A high-risk pregnancy is one where the mother or the fetus has an increased risk of adverse outcomes compared to uncomplicated pregnancies. No concrete guidelines currently exist for distinguishing “high-risk” pregnancies from “low-risk” pregnancies, however there are certain studied conditions that have been shown to put the mother or fetus at a higher risk of poor outcomes. These conditions can be classified into three main categories: health problems in the mother that occur before she becomes pregnant, health problems in the mother that occur during pregnancy, and certain health conditions with the fetus.
In 2012, the CDC estimated that there were approximately 65,000 pregnancies deemed "high-risk" in the United States.
Causes
Mother-related factors
Pregnancies could be considered high risk if the mother has certain pre-existing health conditions. These include:
* Age
** Older age - Pregnancies in women over the age of 35 are considered "
advanced age". First-time pregnant women in this age group may have normal pregnancies, but research indicates that these women are at increased risk of having: first trimester miscarriage, chromosomal abnormalities in the fetus, and
fetal growth restriction
Intrauterine growth restriction (IUGR), or fetal growth restriction, refers to poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...
(FGR).
Advanced age is associated with a higher risk for fetal chromosomal abnormalities such as
Down Syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...
(Trisomy 21) and
Trisomy 13
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
.
Some of these chromosomal abnormalities are further associated with an increased risk of miscarriage in the first trimester. It is not yet well-understood how older age leads to increased risk of FGR, but studies have suggested that it could be related to placenta dysfunction.
** Younger age -
Pregnant teenagers are more likely to develop
anemia
Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...
, have preterm births, and have low birth weight babies.
*Chronic high blood pressure - The CDC estimates the rate of chronic hypertension in the US as 166.9 per 100,000 hospital deliveries. Hypertension is considered a risk factor for high-risk pregnancy because it leads to an increased risk of
pre-eclampsia
Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease ...
,
restricted fetal growth, and
preterm birth
Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks Gestational age (obstetrics), gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 we ...
.
It is not yet well-understood how hypertension leads to increased risk of these outcomes. However, it is thought that hypertension leads to decreased blood flow to the
placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
.
Decreased blood flow to the fetus could lead to restricted growth and trigger other changes that increase the risk of pre-eclampsia, restricted fetal growth, and pre-term birth.
*
Pre-existing diabetes - Pre-existing diabetes that is not managed during pregnancy is associated with increased risk of spontaneous abortions in the first few weeks of pregnancy and increased risk of congenital malformations such as
congenital heart defects
A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...
and
neural tube defects
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo b ...
.
The mechanism through which hyperglycemia results in these malformations is still an area being studied, but increased oxidative stress resulting from hyperglycemia is a potential contributor. Pre-existing diabetes is also associated with an increased risk of high birth weight or
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 ...
and preterm birth. Macrosomia can put the fetus at risk of
brachial plexus
The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...
injury due to
shoulder dystocia
Shoulder dystocia is when, after vaginal delivery of the head, the baby's anterior shoulder gets caught above the mother's pubic bone. Signs include retraction of the baby's head back into the vagina, known as "turtle sign". Complications for th ...
during vaginal delivery.
* Cardiac/heart disease - During pregnancy, there is an increase in the volume of circulating blood. In women with cardiac disease, this increased blood volume can worsen/exacerbate
existing heart disease.
*
Autoimmune disease
An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. At least 80 types of autoimmune diseases have been identified, with some evidence suggesting that there may be more than 100 types. Nearly a ...
Fetal-related factors
In some pregnancies, certain conditions that arise in the developing fetus or fetuses can put a pregnancy into a high risk category. In these situations, special care must be taken during the pregnancy to address these factors while the fetus is still in the womb to reduce the chances of morbidity and mortality. Common fetal related factors that can create a high risk pregnancy include:
*
congenital 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 ...
*
multiple gestations
*
fetal growth restriction
Intrauterine growth restriction (IUGR), or fetal growth restriction, refers to poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...
Pregnancy-related factors
Other reasons a pregnancy may be classified as high-risk include if the mother develops a medical condition during pregnancy or if complications occur during pregnancy.
* ''Conditions developed during pregnancy:''
**
Preeclampsia
Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease ...
: Preeclampsia is a syndrome marked by a sudden increase in the blood pressure of a pregnant woman after the 20th week of pregnancy. It can affect the mother's kidneys, liver, and brain. When left untreated, the condition can be fatal for the mother and/or the fetus and result in long-term health problems.
**
Eclampsia
Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
: Eclampsia is a more severe form of preeclampsia, marked by seizures and coma in the mother.
**
HELLP Syndrome
HELLP syndrome is a complication of pregnancy; the acronym stands for hemolysis, elevated liver enzymes, and low platelet count. It usually begins during the last three months of pregnancy or shortly after childbirth. Symptoms may include feelin ...
**
Gestational diabetes
Gestational diabetes is a condition in which a woman without diabetes develops high blood sugar levels during pregnancy. Gestational diabetes generally results in few symptoms; however, it increases the risk of pre-eclampsia, depression, and of ...
: Gestational diabetes (GDM) is diabetes that first develops when a woman is pregnant. Many women can have healthy pregnancies if they manage their diabetes, following a diet and treatment plan from their health care provider. Uncontrolled gestational diabetes increases the risk for adverse perinatal outcomes such as preterm labor and delivery, preeclampsia, and other hypertension-related conditions in pregnancy. Additionally, some evidence suggests that GDM is associated with long-term outcomes such as development of
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, ...
in the mother and future obesity in the infant.
* ''Timing of pregnancy:''
**
Preterm birth
Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks Gestational age (obstetrics), gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 we ...
(infants born before 37 weeks of pregnancy)
***
PROM
A promenade dance, commonly called a prom, is a dance party for high school students. It may be offered in semi-formal black tie or informal suit for boys, and evening gowns for girls. This event is typically held near the end of the school yea ...
(Pre-labor Rupture of Membranes)
**
Post-term pregnancy (infants born after 42 weeks of pregnancy)
* ''Placenta -'' The
placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
is a structure within the uterus that facilitates exchange of nutrients, oxygen, and waste products between the mother and the fetus. When this connection between mother and fetus is abnormally positioned, the pregnancy is more complicated and requires careful delivery technique.
**
Placental abruption
Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dangerou ...
**
Placenta accreta
Placenta accreta occurs when all or part of the placenta attaches abnormally to the '' myometrium'' (the muscular layer of the uterine wall). Three grades of abnormal placental attachment are defined according to the depth of attachment and invas ...
* ''
Infections
An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
-'' Different types of infections may be spread from mother to fetus, predisposing adverse pregnancy outcomes. An existing infection in the mother may be passed along to the fetus during pregnancy through the placenta. A newborn infant is also directly exposed to pathogens during delivery through the vaginal canal or breastfeeding. Fetal infections that develop during pregnancy may trigger spontaneous abortion or affect typical fetal growth and development. Several infections that are notably associated with pregnancy include
Group B streptococcus
''Streptococcus agalactiae'' (also known as group B streptococcus or GBS) is a gram-positive coccus (round bacterium) with a tendency to form chains (as reflected by the genus name '' Streptococcus''). It is a beta- hemolytic, catalase-negative ...
,
Bacterial vaginosis
Bacterial vaginosis (BV) is a disease of the vagina caused by excessive growth of bacteria. Common symptoms include increased vaginal discharge that often smells like fish. The discharge is usually white or gray in color. Burning with urination ...
,
yeast infections, and
Zika virus
''Zika virus'' (ZIKV; pronounced or ) is a member of the virus family ''Flaviviridae''. It is spread by daytime-active ''Aedes'' mosquitoes, such as '' A. aegypti'' and '' A. albopictus''. Its name comes from the Ziika Forest of Uganda, whe ...
. Some of these infections may be rare but are associated with significant infant morbidity and mortality, particularly if the infection spreads throughout the fetal nervous system. Early evidence shows that
COVID-19
Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
maternal infection in pregnancy may increase adverse outcomes such as preeclampsia.
*
Twin-to-twin transfusion syndrome
Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS), twin oligohydramnios-polyhydramnios sequence (TOPS) and stuck twin syndrome, is a complication of monochorionic multiple pregnancies (the most common ...
Management
Management of high risk pregnancy is dependent on the specific etiology and situation of each particular pregnancy. Some examples of management for certain conditions include:
* Diabetes: To manage diabetes, self-monitoring using finger stick
blood glucose monitoring
Blood glucose monitoring is the use of a glucose meter for testing the concentration of glucose in the blood ( glycemia). Particularly important in diabetes management, a blood glucose test is typically performed by piercing the skin (typically, ...
is recommended.
Medical nutritional therapy and insulin therapy, as well as anti-hyperglycemic oral medications are also recommended.
* Chronic hypertension: Anti-hypertensive agents that are safe to use during pregnancy should be used to manage hypertension during pregnancy. ACOG also recommends low dose aspirin in pregnant women who have chronic hypertension and other pre-eclampsia risk factors.
* Congenital defects: The management of congenital defects in the fetus depends on the specific condition. For example, certain cardiac anomalies must be corrected to avoid irreversible damage during the gestational period, such as using fetal cardiac catheterization to correct pulmonary atresia with intact ventricular septum. Spina Bifida is another common condition that can be repaired before birth. Other anomalies, such as hypoplastic left heart syndrome, can be monitored throughout the pregnancy and treated with surgery soon after birth.
* Multiple gestations: Although conditions that are more common in multiple gestations, such as preterm birth, should be monitored properly during the pregnancy, there is currently limited evidence to evaluate the ability of specialized antenatal care on improving outcomes for the parent or infant.
*
Infections
An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmiss ...
: Early and regular prenatal care is important. A provider should be consulted about options including prevention via medication prophylaxis or vaccines, and treatment such as appropriate use of antibiotics (ex. for
congenital syphilis
Congenital syphilis is syphilis present ''in utero'' and at birth, and occurs when a child is born to a mother with syphilis. Untreated early syphilis infections results in a high risk of poor pregnancy outcomes, including saddle nose, lower ext ...
) or antifungals. Another option for prevention of transmission includes delivery via
Caesarian delivery.
Anxiety surrounding "high-risk pregnancy" label
The concept of a high risk pregnancy has been shown to elicit a strong emotional response in some pregnant women, including fear, anger, and guilt. In addition, some studies show that a pregnancy labeled "high risk" may lead to more unnecessary testing than without the label, increasing these fears and reducing the pregnant woman's sense of control over the situation. Managing anxiety in pregnancies deemed high risk has been deemed an important focus in research, although there is currently limited high quality studies on the issue.
References
{{reflist
Pathology of pregnancy, childbirth and the puerperium
Grief
Sex chromosome aneuploidies