Lactation: Why Menstruation Stops During Breastfeeding

Lactation

Why is it that during the lactation period, menstruation does not occur (or is suppressed)? Is this statement correct? What is the relationship with lactation hormones or oxytocin (OT)? What is the correct mechanism? Could you please provide detailed information?

herbnet, 20~29 year old female. Ask Date: 2001/07/11

Dr. Lin Zhaopei reply Obstetrics and Gynecology

During the lactation period, the pituitary gland secretes a significant amount of prolactin, which inhibits the secretion of ovulatory hormones from the brain, resulting in a temporary absence of menstruation.
However, once the lactation period exceeds three months, this inhibitory effect gradually diminishes, which is why some women who breastfeed for an extended period may experience the return of their menstrual cycle.
Prolactin is primarily secreted during childbirth and when the infant suckles; it facilitates milk ejection and uterine contractions, aiding in the rapid recovery of the uterus postpartum.
However, it does not have an impact on the presence or absence of menstruation.

Reply Date: 2001/07/11

More Info

During lactation, many women experience a temporary cessation of menstruation, a phenomenon known as lactational amenorrhea. This is a normal physiological response that can be attributed to hormonal changes in the body during breastfeeding. Understanding the mechanisms behind this can provide insight into the relationship between lactation and menstruation.

The primary hormones involved in lactation are prolactin and oxytocin. Prolactin is produced by the anterior pituitary gland and plays a crucial role in milk production. When a baby suckles at the breast, nerve signals are sent to the hypothalamus, which stimulates the release of prolactin. Elevated levels of prolactin not only promote milk synthesis but also inhibit the secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. GnRH is essential for the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland, which are critical for the menstrual cycle.

As prolactin levels remain high during breastfeeding, the suppression of GnRH leads to decreased levels of LH and FSH. This hormonal imbalance prevents the ovaries from producing estrogen and progesterone, the hormones necessary for ovulation and the menstrual cycle. Consequently, menstruation is delayed or may stop altogether during the breastfeeding period.

The duration of lactational amenorrhea can vary significantly among women. Factors such as the frequency and duration of breastfeeding sessions, the introduction of supplementary feeding, and individual hormonal responses can influence how long menstruation remains absent. For instance, exclusive breastfeeding (where the infant receives only breast milk) typically leads to a longer duration of amenorrhea compared to mixed feeding (breast milk along with formula or solid foods).

It's important to note that while lactational amenorrhea can be a natural form of contraception, it is not foolproof. Ovulation can occur before the first postpartum period, meaning that it is possible for a woman to conceive again while still breastfeeding, even if she has not yet resumed menstruation.

In summary, the cessation of menstruation during lactation is primarily due to the elevated levels of prolactin, which inhibit the hormonal signals necessary for ovulation and menstruation. This natural mechanism allows the body to focus on nurturing the newborn while also providing a temporary form of birth control. However, individual experiences may vary, and it is essential for breastfeeding mothers to be aware of their bodies and consult healthcare providers for personalized advice regarding menstruation and fertility during this period.

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