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Prenatal nutrition addresses nutrient recommendations before and during pregnancy. Nutrition and
weight management Weight management includes the techniques and physiological processes that contribute to a person's ability to attain and maintain a certain weight. Most weight management techniques encompass long-term lifestyle strategies that promote healthy ...
before and during
pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...
has a profound effect on the development of
infants An infant or baby is the very young offspring of human beings. ''Infant'' (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is a formal or specialised synonym for the common term ''baby''. The terms may also be used to ...
. This is a rather critical time for healthy development since infants rely heavily on maternal stores and nutrient for optimal growth and health outcome later in life. Prenatal nutrition has a strong influence on
birth weight Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European descent is , with the normative range between . On average, babies of South Asian and Chinese descent weigh about . As far as low birth weight ...
and further development of the infant. There was a study at the National Institution of Health which found that babies born from an obese mother have a higher probability to fail tests of fine motor skills which is the movement of small muscles such as the hands and fingers. A common saying that a woman "is eating for two" while pregnant implies that a mother should consume twice as much during pregnancy, but is misleading. Although maternal consumption will directly affect both herself and the growing
fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...
, overeating excessively will compromise the baby's health as the infant will have to work extra hard to become healthy in the future. Compared with the infant, the mother possesses the least biological risk. Therefore, excessive calories, rather than going to the infant, often get stored as fat in the mother. On the other hand, insufficient consumption will result in lower birth weight. Maintaining a healthy weight during
gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
lowers adverse risks on infants such as
birth defects A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
, as well as chronic conditions in adulthood such as
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
,
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
, and
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
(CVD). Ideally, the rate of weight gain should be monitored during pregnancy to support the most ideal infant development.


Background


Barker's hypothesis – influences of birth weight on health in later life

The "Barker Hypothesis", or
Thrifty phenotype Thrifty phenotype refers to the correlation between low birth weight of neonates and the increased risk of developing metabolic syndromes later in life, including type 2 diabetes and cardiovascular diseases. Although early life undernutrition is th ...
, states that conditions during pregnancy will have long-term effects on adult health. Associated risk of lifelong diseases includes
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
,
type-2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...
,
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
, and
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
. Babies born lighter in weight appear to have an increased rate of mortality than babies born at a heavier weight. This does not mean that heavy babies are less of a concern. Death rate would rise as birth weight increases beyond normal birth weight range. Therefore, it is important to maintain a healthy
gestational weight gain right Gestational weight gain is defined as the amount of weight gain a woman experiences between conception and birth of an infant. Recommendations The Institute of Medicine (IOM) recommendations for gestational weight gain are based on body m ...
throughout pregnancy for achieving the optimal infant birth weight. When this theory was first proposed, it was not well accepted and was met with much skepticism. The main criticism was that
confounding In statistics, a confounder (also confounding variable, confounding factor, extraneous determinant or lurking variable) is a variable that influences both the dependent variable and independent variable, causing a spurious association. Con ...
variables such as environmental factors could attribute to many of the chronic diseases such that low birth weight alone should not be dictated as an independent risk factor. Subsequent research studies supporting the theory attempted to adjust these environmental factors and in turn, provided more convincing results with minimal confounding variables. "Barker's Hypothesis" is also known as " Fetal Programming Hypothesis". The word "programming" illustrates the idea that during critical periods in early fetal development, there are persisting changes in the body structure and function that are caused by environmental stimuli. This relates to the concept of developmental plasticity where our genes can express different ranges of physiological or morphological states responding to the environmental conditions during fetal development. If the mother has an inadequate diet then it signals the baby that the living condition in the long term will be impoverished. Consequently, the baby adapts by changing its body size and metabolism to prepare for harsh conditions of food shortages after birth. Physiological and metabolic processes in the body undergo long-term changes as a result of restricted growth. When the living environment switches from the condition of malnutrition to a society of abundant supply of nutrients, this exposes the baby to a bountiful environment that goes against what its body is designed for and this places the baby at a higher risk of adult diseases later in adulthood. By the same token, if the fetus growing in the womb of a healthy mother is exposed to prolonged famine after birth, the infant would be less adaptive to the harsh environment than low-birth-weight babies.


Pedersen's hypothesis – influences of maternal glucose concentration on fetal growth

In 1952, the Danish physician
Jørgen Pedersen Jørgen Pedersen (1914–1978) was an Epidemiologist. He is known for his hypothesis concerning the correlation of hyperglycemia during pregnancy and disease in later life. Life and work In 1952 he formulated the hypothesis that hyperglycemia i ...
of the
University of Copenhagen The University of Copenhagen ( da, Københavns Universitet, KU) is a prestigious public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in ...
, formulated the hypothesis that maternal hyperglycemia during pregnancy might cause fetal
hyperglycemia Hyperglycemia is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a blood sugar level higher than 11.1 mmol/L (200  mg/dL), but symptoms may not start to become noticeable until even ...
, thus exposing the fetus to elevated insulin levels. This would result in an increased risk of fetal macrosomia and neonatal hypoglycemia. The
blood glucose Glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood of humans or other animals. Approximately 4 grams of glucose, a simple sugar, is present in the blo ...
concentration in humans is mainly dependent on
diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...
, especially energy-ingestion and the percentage of
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
s in the diet. High glucose concentrations in the blood of pregnant women cause an intensified transfer of nutrient to the fetus, increasing fetal growth. Studies could link higher maternal glucose to an increase in infant birth weight as well as different extents of morbidity, among other things the incidence of congenital malformations, supporting the Hypothesis, that even moderately increased blood glucose in the absence of diabetes positively influences growth in the fetus. Subsequently, alterations of Pedersen's Hypothesis took place:
Nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
s other than sugar and their linkage to fetal overgrowth in
diabetic Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level (hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased app ...
pregnancy were taken into account, too, but the crucial role of the fetal
hyperinsulinism Hyperinsulinism refers to an above normal level of insulin in the blood of a person or animal. Normal insulin secretion and blood levels are closely related to the level of glucose in the blood, so that a given level of insulin can be normal for on ...
and monitoring of motherly glucose was nevertheless stressed. Recent studies pointed out that diabetes in the mother could foster even more lasting effects on the child's health than previously thought, even raising the risk of
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
and
type 2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...
.


Historical cases

Various nutritional conditions, both times of
scarcity In economics, scarcity "refers to the basic fact of life that there exists only a finite amount of human and nonhuman resources which the best technical knowledge is capable of using to produce only limited maximum amounts of each economic good. ...
and of
abundance Abundance may refer to: In science and technology * Abundance (economics), the opposite of scarcities * Abundance (ecology), the relative representation of a species in a community * Abundance (programming language), a Forth-like computer prog ...
occurred time and again in different societies at different times, and thus in some cases epidemiological studies have exposed a
correlation In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics ...
between the nutritional status of pregnant women and the health of their children or even grandchildren.


The Dutch famine

Since small birth weight is associated with an increased risk of chronic diseases in later life, and poor maternal nutrition during gestation contributes to restricted fetal development, maternal malnutrition may be a cause of increased disease susceptibility in adulthood. The
Dutch famine of 1944 Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...
or the "Hunger Winter" during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
serves as an epidemiological study that is used to examine the effects of maternal under-nutrition during different gestational stages. The famine was a period (roughly five to six months) of extreme food shortage in the west of the Netherlands. The famine was imposed on a previously well-nourished population and the official daily
ration Rationing is the controlled distribution of scarce resources, goods, services, or an artificial restriction of demand. Rationing controls the size of the ration, which is one's allowed portion of the resources being distributed on a particular ...
for the general adult population gradually decreased from 1800 calories in December 1943 to 1400 calories in October 1944 to below 1000 calories in the late November 1944. December 1944 to April 1945 was the peak of the famine where the official daily ration fell abruptly to about 400~800 calories. Even though pregnant and lactating women had extra food during the famine, these extra supplies could no longer be provided peaking the famine. In the early May 1945, the liberation of the Netherlands restored the food supply. The daily ration had increased to more than 2000 calories in June 1945. What is unique about Dutch Famine as an experimental study on the effects of maternal malnutrition is that the population was strictly circumscribed in time and place and the sudden onset and relief of the famine was imposed on a previously well-nourished population. The Dutch Famine during World War II had a profound effect on the health condition of the general public, especially women who conceived during the period of time. The period of maternal starvation is shown to have limited intrauterine growth and has been identified as one of the most important contributors to
coronary heart disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pla ...
as well as other chronic diseases later in life. These findings agree well with Barker's hypothesis; it supports the theory that maternal under-nutrition leads to a lower birth weight due to restricted intrauterine development and ultimately leads to higher risks of chronic conditions in adult life.


The French paradox

The
French paradox The French paradox is an apparently paradoxical epidemiological observation that French people have a relatively low incidence of coronary heart disease (CHD), while having a diet relatively rich in saturated fats, in apparent contradicti ...
regards the seemingly paradoxical fact that people living in France since many generations suffer from a relatively little incidence of
heart disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, hea ...
, although the traditional
French cuisine French cuisine () is the cooking traditions and practices from France. It has been influenced over the centuries by the many surrounding cultures of Spain, Italy, Switzerland, Germany and Belgium, in addition to the food traditions of the re ...
is high in saturated fatty acids. One explanation suggested for the paradox is the potential impact of nutritional enhancements during pregnancy and the first months and years of life that would positively influence the health of following generations: After the defeat in the Franco-German War, a nutrition program for pregnant women and small children with the aim of strengthening future generations of soldiers was introduced by the French Government. This might be one explanation for positive health-outcomes in following generations.


Recommendations for pregnant women


Gestation stages

Gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
is the period of
embryo development An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
from conception to birth. Gestation is about 40 weeks in humans and is divided into three
trimesters Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but can ...
, each spanning 3 months. Gestational stages, on the other hand, are based on physiological fetal development, which include the germinal stage, embryonic stage and fetal stage. Germinal stage is the stage from fertilization to about 2 weeks. The fertilized egg or the zygote becomes a blastocyst where the outer layer and the inner cell mass differentiate to form placenta and the fetus respectively. Implantation occurs at this stage where the blastocyst becomes buried in the
endometrium The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional laye ...
. Embryonic stage is approximately from 2 weeks to 8 weeks. It is also in this stage where the blastocyst develops into an
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
, where all major features of humans are present and operational by the end of this stage. Fetal stage is from 9 weeks to term. During this period of time, the embryo develops rapidly and becomes a
fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...
. Pregnancy becomes visible at this stage. File:Color10 weeks pregnant.jpg, Embryo at 8 weeks after fertilization File:Color20 weeks pregnant.jpg, Fetus at 18 weeks after fertilization File:Color40 weeks pregnant.jpg, Fetus at 38 weeks after fertilization


Pre-pregnancy weight and gestational weight gain

The pattern and amount of weight gain is closely associated with gestational stages. Additional energy is required during pregnancy due to the expansion of maternal tissues and stored to support fetal development. In the
first trimester Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...
(blastogenesis and early embryonic stages), the mother experiences a minimal weight gain (approximately 0.5-2 kilograms), while the
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
weighs only 6 grams. In the
second trimester Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...
and
third trimester Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but can ...
(late embryonic and fetal stages), the fetus undergoes rapid weight growth and the weight increases to about 3000~4000 grams. It is also in this period that the mother experiences the bulk of her gestational weight gain but the amount of weight gain varies greatly. The amount of weight gain depends strongly on their pre-pregnant weight. Generally, a normal weight is strongly recommended for mothers when entering gestation, as it promotes overall health of infants. Maternal body weight is determined by the
Body Mass Index Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m2, resulting from mass in kilograms and he ...
(BMI) which is defined as the weight in kilograms divided by the square of the height in meters. While pregnant, body weight should be managed within the recommended gestational weight gain range as it is shown to have a positive effect on pregnancy outcomes. Gestational weight gain should also be progressive and the recommended weight depends on pre-pregnant body weight. Since the total weight gain depends on pre-pregnant body weight, it is recommended that underweight women should undergo a larger weight gain for healthy pregnancy outcomes, and overweight or obese women should undergo a smaller weight gain.


Normal weight women

Women having a BMI of 18.5~24.9 are classified as having a ''normal or healthy'' body weight. This group has the lowest risk of adverse birth outcomes. Their babies are least likely to either be low-birth weight or high-birth weight. It is advised that women with a normal weight before pregnancy should gain a total of 11.5 kilograms to 16.0 kilograms throughout gestation, which is approximately 0.4 kilogram per week in the second and third trimesters. In order to maintain a steady weight gain, the mother should engage in mild physical activities. Participating in
aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cellu ...
activities such as walking and swimming 3 to 4 times a week is usually adequate. Vigorous physical activity is not recommended since an excessive loss of calories is induced which is not sufficient to support fetal development. A proper diet is also essential to healthy weight gain. The common saying "a woman is eating for two" often leads to mothers thinking that they should eat twice as much. In reality, only a small increase in caloric intake is needed to provide for the fetus; approximately 350 calories more in the second trimester and 450 calories more in the third trimester. Also, healthy choices should be emphasized for these extra calories such as
whole grain A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm. As part of a general healthy diet, consumption of whole grains is associated w ...
products,
fruits In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particula ...
and vegetables as well as low-fat dairy alternatives.


Underweight women

Women are classified as ''underweight'' if they have a pre-pregnant BMI of 18.5 or below. Low pre-pregnancy BMI increases the risk of low birth weight infants, but the risk can be balanced by an appropriate gestational weight gain from 12.5 to 18.0 kilograms in total, or about 0.5 kilogram each week in the second and third trimesters. Underweight women usually have inadequate nutrient stores that are not enough to provide for both herself and the fetus. While exercise and a proper diet are both needed to maintain the recommended weight gain, a balance between the two is very important. As such, underweight mothers should seek individualized advice tailored especially for themselves.


Overweight and obese women

Women with a high pre-pregnancy weight are classified as ''overweight or obese'', defined as having a BMI of 25 or above. Women with BMI between 25 and 29.9 are in the overweight category and should gain between 7.0 and 11.5 kilograms in total, corresponding to approximately 0.28 kilogram each week during the second and third trimesters. Whereas women with BMI of 30 or above are in the obese category and should gain only between 5.0 and 9.0 kilograms overall, which equates to roughly 0.2 kilogram per week in the second and third trimesters. Diet, exercise or a combination of both has been seen to reduce weight gain in pregnancy by 20% and reduce high blood pressure. Diet with exercise may reduce the risk of caesarean section, having a large baby and having a baby with serious breathing problems. Diet and exercise help pregnant women not gain too much weight during pregnancy when compared with giving the women no help to control weight gain or routine care (usually one session in the pregnancy). In general, walking is encouraged for mothers classified in this category. Unfortunately, estimated energy requirements for them are not available. As such, they are encouraged to record activity and intake level. This can be done with the help of tools such as My Food Guide Servings Tracker from
Health Canada Health Canada (HC; french: Santé Canada, SC)Health Canada is the applied title under the Federal Identity Program; the legal title is Department of Health (). is the Structure of the Canadian federal government#Departments, with subsidiary unit ...
and EATracker that are available online. In extreme cases where the BMI exceeds 35, help from a registered
dietitian A dietitian, medical dietitian, or dietician is an expert in identifying and treating disease-related malnutrition and in conducting medical nutrition therapy, for example designing an enteral tube feeding regimen or mitigating the effects of ca ...
is recommended.


Summary table

The following table summarizes the recommended rate of weight gain and total weight gain according to pre-pregnancy BMI for singleton pregnancies. The first column categorizes the type of body weight based on the Body Mass Index. The second column summarizes the total recommended weight gain for each type of body weight, and the third column presents the corresponding weekly weight gain during the period when the fetus undergoes rapid growth (during second and third trimesters). In extreme cases, the amount of total and weekly weight gain can vary by a factor of two depending on a woman's pre-pregnant weight. For example, a woman in the obese category is recommended to gain a total of 5~9 kilograms, whereas an underweight woman needs to gain up to 18 kilograms in weight. .


Recommendations for low and high birth weight


Diagnosis

To have a good estimate of birth weight,
ultrasonography Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...
or
ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
during pregnancy and the date of last menstrual period are needed. Measured values from ultrasonography are compared with the growth chart to estimate fetal weight. Crown-rump length can be used as the best ultrasonographic measurement for correct diagnosis of gestational age during the first trimester. This correlation between crown-rump length and gestational age would be most effectively shown when no growth defects are observed in the first trimester. If growth defects were observed in the first trimester, then the measurement of the date of last menstrual period becomes quite important since the crown-heel length has become less of a reliable indicator of gestational age. After the 20th week of pregnancy, the mother would need to visit the doctor for the measurement of
fundal height Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess fetal growth and development during pregnancy. It is measured from the top of the mother's uterus to the top of the mother's pubic symphysis. Fundal height, ...
, which is the length from the top portion of the uterus to the pubic bone."Small for Gestational Age"
''Lucile Packard Children's Hospital'', 2010. Retrieved 9 November 2010.
The length measured in centimeters should correspond to the number of weeks that the mother has been pregnant. If the measured number is higher or lower than 2 centimeters, further tests using ultrasound would be needed to check the results. Another way to estimate fetal size is to look at the mother's weight gain. How much weight the mother gains can be used to indicate fetal size.


Low birth weight

There are two ways to determine
small for gestational age Small for gestational age (SGA) newborns are those who are smaller in size than normal for the gestational age, most commonly defined as a weight below the 10th percentile for the gestational age. Causes Being small for gestational age is broadly ...
(SGA) infants. Many research studies agree that SGA babies are those with birth weight or crown-heel length measured at two
standard deviations In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while ...
or more below the mean of the infant's gestational age, based on data consisting of a reference population. Other studies classify SGA babies as those with birth weight values below the 10th percentile of the growth chart for babies of the same gestational age. This indicates that these babies are weighing less than 90% of babies of the same gestational age. Many factors, including maternal, placental, and fetal factors, contribute to the cause of impaired fetal growth. There are a number of maternal factors, which include age, nutritional status, alcohol use, smoking, and medical conditions. Insufficient uteroplacental perfusion is an example of a placental factor. Chromosomal abnormalities and genetic diseases are examples of fetal factors. Identification of the causes of SGA for individual cases aids health professionals in finding ways to handle each unique case.Lisa Gourley
"Prenatal Nutrition"
''Healthline Networks, Inc.'', 2002. Retrieved 5 November 2010.
Nutritional counseling, education, and consistent monitoring can be helpful to assist women bearing SGA infants. Complications for the infant include limitations in body growth since the number and size of cells in tissues is smaller. The infant likely did not receive enough oxygen during pregnancy so the oxygen level is low. It is also more difficult to maintain body temperature since there is less blood flow within the small body. As such, it is necessary to monitor oxygen level to make sure that it doesn't go too low. If the baby can't suck well, then it may be necessary for tube-feed. Since the baby cannot maintain body temperature sufficiently, a temperature-controlled bed would help to keep their bodies from losing heat. There are ways to help prevent SGA babies. Monitoring fetal growth can help identify the problem during pregnancy well before birth. It would be beneficial to seek professional help and counseling.


High birth weight

Research shows that when birth weights of infants are greater than the 90th percentile of the
growth chart A growth chart is used by pediatricians and other health care providers to follow a child's growth over time. Growth charts have been constructed by observing the growth of large numbers of healthy children over time. The height, weight, and head ...
for babies of the same gestational age, they are considered
large for gestational age Large for gestational age (LGA) is a term used to describe infants that are born with an abnormally high weight, specifically in the 90th percentile or above, compared to other babies of the same developmental age. Macrosomia is a similar term tha ...
or LGA.Children's Hospital of Wisconsin
"Large for Gestational Age"
''Children's Hospital and Health System'', 2010. Retrieved 9 November 2010.
This indicates that these babies are weighing more than 90% of babies of the same gestational age. Many factors account for LGA babies, including
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
and excessive nutrient supply. It seems that a common factor for LGA babies is whether or not the mother has diabetes when she is pregnant. An indicator for excessive growth, regardless of gestational age, is the appearance of
macrosomia Large for gestational age (LGA) is a term used to describe infants that are born with an abnormally high weight, specifically in the 90th percentile or above, compared to other babies of the same developmental age. Macrosomia is a similar term tha ...
.BabyCenter Medical Advisory Board
"Labor complication: Big baby (macrosomia)"
''BabyCenter, L.L.C.'', 2006. Retrieved 5 November 2010.
Many complications are observed for LGA babies and their mothers. A longer delivery time may be expected since it is a difficult birth. The infant would likely suffer hypoglycemia (low glucose level in the blood) after birth. The infant would also have difficulty breathing. There might be a need for early delivery if the baby gets too big and perhaps
Caesarean section Caesarean section, also known as C-section or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen, often performed because vaginal delivery would put the baby or mo ...
would be needed. Since the baby is bigger, there's a higher chance of injury when coming out of the mother's body. To increase the blood glucose level in blood, a glucose/water solution can be offered to the infant. There are ways to help prevent LGA babies. It is necessary to monitor fetal growth and perform pregnancy examinations to determine health status and detect any possibility of unrecognized diabetes. For diabetic mothers, careful management of diabetes during pregnancy period would be helpful in terms of lowering some of the risks of LGA.


Points to consider

The goal of pregnancy is to have a healthy baby. Maintaining healthy and steady weight gain during pregnancy promotes overall health and reduces the incidence of prenatal
morbidity A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
and
mortality Mortality is the state of being mortal, or susceptible to death; the opposite of immortality. Mortality may also refer to: * Fish mortality, a parameter used in fisheries population dynamics to account for the loss of fish in a fish stock throug ...
. This, in turn, has a positive effect on the baby's health. Since conditions during pregnancy will have long-term effects on adult health, "moderation" should be considered for both dietary and physical activity recommendations. Most importantly, the total recommended pregnancy weight gain depends on pre-pregnant body weight, and weight issues should be addressed before pregnancy.


Research


Malnutrition and the placenta

The placenta may adapt to maternal malnutrition in an effort to support fetal development and protect against adverse nutritional exposures. In pregnant mice, undernutrition and high fat diets have been shown to alter both placental size and structure, including the expression of key transport systems. Placentae from mothers fed a high fat diet appeared to adapt to excessive nutrient supply, while placentae from undernourished mothers were less mature with impaired transport. These placental adaptations could help to explain why offspring from malnourished pregnancies experience altered growth.


Future direction for research

It is reasonable to expect higher weight gain for multiple gestations. Recommendations for women carrying twins are given but more research should be done to precisely determine the total weight gain, as these ranges are wide. Also, the ranges for underweight women carrying twins is unknown. There was not enough information to recommend weight gain cutoffs and guidelines for women carrying three or more babies, women of short stature (<157 centimetres), and pregnant teens. Estimated energy requirements (EER) for overweight/obese women are unavailable so more research is needed to evaluate on that. There are also important links between nutrition and mental health across pregnancy. For example, a woman experiencing low mood may be more likely to smoke, use alcohol or neglect her dietEarly life programming as a target for prevention of child and adolescent mental disorders: intervention and research directions. BMC Medicine: Special issue on Prevention of Mental Disorders
12:33


Practical advice for mothers

The following general tips can be helpful to pregnant women. It would be beneficial to maintain adequate physical activity to meet energy needs from the food consumed. Eating a balanced diet would be optimal for healthy pregnancy results.Larissa Hirsch

''The Nemours Foundation'', 2008. Retrieved 17 November 2010.
To prevent problems like dehydration and constipation, it is important to drink enough fluids, especially water, to support blood volume increases during pregnancy.Ministry of Health Promotion
"The Juicy Story on Drinks"
''Queen's Printer for Ontario'', 2010. Retrieved 18 November 2010.
It is recommended to accompany regular meals with a daily prenatal vitamin supplement that has sufficient
folic acid Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...
and iron content. If the fetus is predicted to have low birth weight, in addition to the general recommendations, it would be ideal to increase caloric intake, which can be done by having extra Food Guide Servings daily. If the fetus is predicted to have high birth weight, smaller and more frequent meals should be consumed to allow better weight management. Moderate sugar intake, such as fruit juices, is also suggested.Alberta clinical experts
"Prediabetes or Impaired Glucose Intolerance"
, ''HealthLink Alberta'', 2008. Retrieved 21 November 2010.
It is essential to limit food and beverages with high calories and salt content."Prenatal Nutrition Guidelines for Health Professionals – Background on Canada's Food Guide"
''Health Canada'', 2009. Retrieved 23 November 2010.


See also

*
Smoking and pregnancy Tobacco smoking during pregnancy causes many detrimental effects on health and reproduction, in addition to the general health effects of tobacco. A number of studies have shown that tobacco use is a significant factor in miscarriages among pregn ...
*
Nutrition and pregnancy Nutrition and pregnancy refers to the nutrient intake, and dietary planning that is undertaken before, during and after pregnancy. Nutrition of the fetus begins at conception. For this reason, the nutrition of the mother is important from before co ...
* Fetal Origins Hypothesis * Fetal Programming


References

{{Pregnancy Health issues in pregnancy Midwifery