Ovulation and the return of the menstrual cycle can lead to a noticeable, though typically temporary, reduction in milk supply for some individuals. This fluctuation is a common physiological event that occurs when the body begins shifting back toward fertility while still maintaining lactation. The hormonal balance governing milk production is highly sensitive to the reintroduction of the reproductive cycle, creating a brief period where milk synthesis slows down. This phenomenon is a short-lived response to natural hormonal shifts, not a sign of permanent low supply.
The Hormonal Mechanism
Milk production operates primarily under the influence of the hormone prolactin, which signals the mammary glands to synthesize milk. During pregnancy and the immediate postpartum period, high levels of estrogen and progesterone suppress the receptors for prolactin, preventing copious milk production until after birth. Once the placenta is delivered, these hormones drop sharply, allowing prolactin to take over and initiate full milk production.
When the body resumes ovulation, it starts producing higher amounts of estrogen and progesterone, particularly during the luteal phase (the time between ovulation and menstruation). These re-emerging reproductive hormones temporarily interfere with lactation by suppressing prolactin receptors in the breast tissue. This hormonal antagonism results in a transient slowdown of milk synthesis.
Beyond the direct hormone interference, the return of the menstrual cycle is also associated with a temporary drop in blood calcium levels. Calcium is an important mineral for milk production and the function of the milk-making cells. This decline in circulating calcium, which happens after ovulation, is thought to be another contributing factor to the observed dip in supply. This dual action—hormonal receptor suppression and mineral fluctuation—is the underlying mechanism behind the temporary reduction in milk volume.
Recognizing the Temporary Change
A mother may first notice the effects of a returning cycle about a week or two after ovulation, aligning with the luteal phase when progesterone levels are highest. The physical sign most commonly observed is a noticeable softening of the breasts, which feel less full or engorged than usual. For those who pump, a measurable decrease in expressed milk volume is a clear indicator of the supply dip.
The baby’s behavior at the breast may also change during this time. Infants might become fussier, pull on and off the nipple, or seem dissatisfied with the flow. This is due to reduced milk flow and a subtle shift in the milk’s taste. Research indicates that during the luteal phase, the milk composition changes: sodium and chloride temporarily increase, making the milk taste slightly saltier, while lactose (milk sugar) decreases, making it less sweet.
This change in supply and taste is typically short-lived and should resolve once the menstrual flow begins or ends, and the levels of estrogen and progesterone return to their baseline. Recognizing this pattern—a brief dip followed by a return to normal—can help distinguish a temporary, cycle-related fluctuation from a persistent issue with low supply. While the milk’s overall nutritional quality is not compromised, proactive management is required to ensure the baby continues to feed effectively.
Strategies for Maintaining Supply
Since the supply dip is related to temporary hormonal and mineral changes, effective strategies focus on maintaining milk removal frequency and supplementing specific nutrients. Increasing the frequency of nursing or pumping sessions is the primary method to counteract the slowdown. Stimulating the breast more often sends frequent signals to the brain to produce prolactin, overriding the temporary hormonal suppression.
For mothers who primarily pump, incorporating a power pumping session daily during the affected week can be highly beneficial. This involves short, frequent pumping intervals designed to mimic a cluster-feeding baby, which effectively boosts prolactin release. Regardless of feeding method, ensuring complete drainage of the breast at each session is important, as residual milk signals the body to slow production.
Nutritional supplementation, specifically with calcium and magnesium, is a targeted strategy to address the mineral drop associated with the luteal phase. Many lactation experts recommend taking a combined calcium and magnesium supplement in a 2:1 ratio, such as 500 mg of calcium with 250 mg of magnesium. This supplementation should begin at the point of ovulation and continue through the first few days of the menstrual period, helping to stabilize the mineral levels that support milk synthesis.
Temporary use of mild galactagogues (substances that help increase milk supply) can also be considered during the dip. Foods like oatmeal are often cited as helpful, and herbal supplements such as fenugreek or blessed thistle may be used for a few days to bridge the temporary gap. These aids should be used alongside increased milk removal, and mothers should consult a healthcare provider or lactation consultant before beginning any new supplement regimen.