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{{more footnotes, date=November 2019 Breastfeeding and fertility are the effects of breastfeeding on the fertility of
postpartum The postpartum (or postnatal) period begins immediately after childbirth Childbirth, also known as labour or delivery, is the ending of pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In ...
women. Hormones associated with lactation and breastfeeding can variably and unreliably inhibit processes involved with fertility. Because of the high variation of this process, breastfeeding is not recommended to be a method of contraception by medical providers. The physiological importance of this inhibition is so that women who are breastfeeding have a decreased likelihood of a subsequent pregnancy while they are still wanting to breastfeed.


Reliability

Breastfeeding Breastfeeding, also called nursing, is the process of feeding a mother's breast milk to her infant, either directly from the breast or by expressing (pumping out) the milk from the breast and bottle-feeding it to the infant. The World Healt ...

Breastfeeding
is not a sole method of postpartum
contraception Birth control, also known as contraception, anticonception, and fertility control, is a method or device used to prevent pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offsp ...
that is recommended by medical providers, because it is so highly variable. There are many factors that contribute to the reliability of using breastfeeding as a method of postpartum contraception. The amount and frequency of breastfeeding, natural or artificial, affect all of these factors. Additionally, they all vary in duration and potency of their effect on
fertility Fertility is the capability to produce offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual reproduction, two organisms. Collective ...
. The time in which a
lactating Lactation describes the secretion of milk Milk is a nutrient A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with ...

lactating
woman does not
menstruate Menstruation (also known as a period and many other colloquial Colloquialism or colloquial language is the linguistic style used for casual (informal) communication Communication (from Latin Latin (, or , ) is a classical lan ...
is called
lactational amenorrhea Lactational amenorrhea, also called postpartum infertility, is the temporary postnatal The postpartum (or postnatal) period begins immediately after childbirth Childbirth, also known as labour or delivery, is the ending of pregnancy ...
.
Amenorrhea Amenorrhea is the absence of a menstrual period The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cy ...
is the medical term that means “no menstruation.” If a woman is not menstruating, her uterine lining is not proliferating and shedding. The purpose of uterine lining proliferation is to provide a favorable environment for a potential fertilized
zygote A zygote (, ) is a eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...

zygote
. A thick uterine lining is rich in grooves and blood vessels. The grooves increase the surface area inside the
uterus The uterus (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of th ...

uterus
, giving the fertilized zygote many different options for locations to
implant Implant can refer to: Medicine *Implant (medicine), or specifically: **Brain implant **Breast implant **Buttock augmentation, Buttock implant **Cochlear implant **Contraceptive implant **Dental implant **Fetal tissue implant **Implantable cardiov ...
. Blood vessels provide the implanted zygote with the sufficient amount of nutrients necessary for its development. Without uterine proliferation, implantation is extremely rare. The length of time in which a postpartum woman does not
ovulate Ovulation is the release of egg An egg is the organic vessel containing the in which an develops until it can survive on its own, at which point the animal hatches. An egg results from of an . Most s, (excluding s), and lay eggs, alth ...

ovulate
is another factor. During ovulation, an egg develops, leaves the
ovary The ovary is an organ found in the female reproductive system The female reproductive system is made up of the internal and external sex organs that function in reproduction of new offspring. In humans, the female reproductive system is im ...

ovary
, and travels down the
fallopian tube The Fallopian tubes, also known as uterine tubes, salpinges (singular salpinx), or oviducts, are tubes that stretch from the ovaries The ovary is an organ found in the female reproductive system 400px, 1. Labia_majora.html"_;"title="V ...

fallopian tube
. There, it will most likely get fertilized if sperm cells are present. If ovulation does not occur, there is no egg present to be fertilized and become a developing zygote. Hormones present during breastfeeding can inhibit ovulation and uterine proliferation. The level of inhibition is highly variable in potency and is not uniform from woman to woman. Time since delivery contributes to the fertility of a postpartum woman as well. There is a direct relationship between time and fertility. As time increases, fertility also increases. Each woman’s body is different and therefore there are no set percentages or data on how much time would increase fertility and by how much. This is why medical providers do not recommend using breastfeeding as a primary method for contraception. Other contraceptive use contributes to postpartum fertility as well. Medical providers will often recommend that sexually active postpartum woman be on some form contraceptive to avoid a subsequent pregnancy if desired, due to the low reliability of breastfeeding as a contraceptive.


Physiology

During pregnancy, levels of
estrogen Estrogens or oestrogens, are a class of natural or synthetic sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid , hypothetical a steroid with ...

estrogen
and
progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

progesterone
are high and stimulate the production of
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical , CH4; is among the simplest organic compounds. In chemistry Chemistry is t ...

dopamine
. Dopamine inhibits the production of
prolactin Prolactin, also known as lactotropin, is a protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir Jo ...
. Because of this, prolactin is not produced during pregnancy. After childbirth, levels of estrogen and progesterone plummet, no longer stimulating the production of dopamine. Without dopamine present, prolactin’s production is no longer inhibited. Both prolactin and
oxytocin Oxytocin (Oxt or OT) is a peptide hormonePeptide hormones or protein hormones are hormones whose molecules are peptides or proteins, respectively. The latter have longer amino acid chain lengths than the former. These hormones have an effect o ...

oxytocin
are needed for breastfeeding to occur. Oxytocin secretion is stimulated by
suckling Breastfeeding, also called nursing, is the process of feeding a mother's breast milk to her infant, either directly from the breast or by expressing (pumping out) the milk from the breast and bottle-feeding it to the infant. The World Healt ...

suckling
. Suckling sends sensory input to the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
where higher brain centers block dopamine and release oxytocin. The presence of oxytocin triggers the secretion of prolactin. Prolactin regulates the production of milk and delivery of that milk into the alveoli of breast tissue where it waits to be excreted. Oxytocin regulates the excretion of milk by targeting the layer of smooth muscle cells that surround the alveoli, causing them to contract. As this muscle contracts, milk is forced out of the alveoli, through ducts, and out of the breast via the nipple. The prolactin that is being secreted during one round of feeding is making milk for the next round of feeding. Oxytocin is expelling milk that was made during the last feeding. A breastfeeding mother’s fertility is decreased because higher amounts of prolactin inhibit
GnRH Gonadotropin-releasing hormone (GnRH) is a releasing hormone Releasing hormones and inhibiting hormones are hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδ ...
through a direct relationship. The less prolactin there is secreted, the less inhibition occurs. Inhibition and fertility have an inverse relationship. The less inhibition that occurs, the higher the fertility rate will be. If there are fewer suckling events, there will be less prolactin production. If suckling ceases, prolactin levels will return to those of a non-pregnant woman.


Importance

If breastfeeding did not have any effect on fertility, then newly postpartum women would have an increased likelihood of getting pregnant. If they were to become pregnant again within the period of time in which they are breastfeeding their newborn, their next pregnancy would inhibit the production of milk as explained above. Breastfeeding’s inhibitory actions prevent, variably and limited as explained above, the occurrence of a subsequent pregnancy.


References

Chao, S. "The Effect of Lactation on Ovulation and Fertility." ''Clinics in Perinatology''. U.S. National Library of Medicine, Mar. 1987. Web. 21 Nov. 2019 McGregor, James A. "Lactation and Contraception." ''SpringerLink''. Springer, Boston, MA, 01 Jan. 1983. Web. 21 Nov. 2019. Planned Parenthood. "Breastfeeding as Birth Control: Information About LAM." ''Planned Parenthood''. N.p., n.d. Web. 21 Nov. 2019. Shaaban, Mamdouh M. "Contraception with Progestogens and Progesterone during Lactation." ''The Journal of Steroid Biochemistry and Molecular Biology''. Pergamon, 17 Jan. 2003. Web. 21 Nov. 2019. Breastfeeding