The absence of a menstrual period while nursing is a common physiological state known as lactational amenorrhea. Many mothers find the return of their cycle to be a confusing and irregular process, often marked by bleeding that seems to start and stop without a clear pattern. This irregularity is a direct result of the complex hormonal adjustments taking place in the body as it balances milk production with the reestablishment of reproductive function. Understanding this transition can clarify why the menstrual cycle behaves so erratically during the breastfeeding phase.
How Breastfeeding Delays Menstruation
The primary mechanism responsible for menstrual suppression during lactation centers on the hormone prolactin, which is released from the pituitary gland to stimulate milk production. When a baby latches and suckles, nerve signals travel from the nipple to the mother’s brain, triggering a surge in prolactin levels. These high, sustained levels of prolactin act as a natural inhibitor on the reproductive system.
Prolactin achieves this inhibition by suppressing the release of Gonadotropin-releasing hormone (GnRH) from the hypothalamus. GnRH is the master hormone that signals the pituitary gland to release the hormones necessary for a menstrual cycle to begin. Prolactin specifically impacts the activity of neurons that regulate the GnRH pulse generator.
The suppression of GnRH prevents the regular pulsatile release of Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). Without sufficient levels of LH and FSH, the ovaries cannot mature an egg or initiate the hormonal cascade required for ovulation. Preventing ovulation effectively prevents menstruation, as a true period is the shedding of the uterine lining after failed ovulation.
Why Your Period Starts and Stops
The eventual return of menstruation signals that the hormonal suppression caused by prolactin is beginning to weaken. This change is often triggered by a decrease in the frequency or intensity of milk removal from the breast. Factors like the baby sleeping longer stretches overnight or a reduction in daytime nursing cause prolactin levels to drop.
When prolactin levels fall below the threshold for full suppression, the reproductive system attempts to restart the menstrual cycle. This attempt is often unsuccessful because remaining prolactin still exerts an inhibitory effect on ovarian hormones. The body may begin follicular development and build up the uterine lining, but fail to release an egg or complete the full cycle.
This partial hormonal activity results in light bleeding or spotting, which is an incomplete menstrual cycle. Since prolactin levels fluctuate based on feeding consistency, the spotting often stops until the body attempts another cycle restart. Introducing solid foods or supplemental formula can also accelerate this process by reducing nursing demand, leading to erratic bleeding.
Pumping sessions, while effective for milk removal, may not always provide the same intensity of neural stimulation as direct nursing. The resulting inconsistency in hormonal signaling means that the first few cycles are commonly shorter, lighter, or consist of intermittent bleeding rather than a predictable, full flow. This “start and stop” pattern is a normal indication of the reproductive axis slowly reactivating.
When Irregular Bleeding Requires a Doctor Visit
While irregular and intermittent bleeding is typical while nursing, it is important to distinguish this normal irregularity from signs of a potential medical concern. The presence of lochia, the normal postpartum discharge, can also complicate the picture as it can last for up to six weeks after birth. Concerning bleeding typically involves excessive volume or associated symptoms.
You should seek immediate medical attention if you experience signs of a potential complication, such as a late-onset postpartum hemorrhage.
Warning Signs Requiring Evaluation
- Extremely heavy bleeding that soaks through more than one standard sanitary pad per hour for two consecutive hours.
- Passing very large blood clots, specifically any clot larger than a golf ball.
- Bleeding accompanied by a fever, which may suggest an infection.
- Experiencing severe, unrelenting pelvic pain.
- Bleeding that had stopped completely for several weeks and then suddenly resumes with a heavy flow.