Milk Production and Menses: What's the Connection?

“I’ve heard that milk production can drop when I get my period. Is that true? Does that mean I won’t have enough milk for my baby?” Concerns about milk production top the “worry list” for many new parents. [1] Among these worries is whether the return of the menses will affect milk production. But keep in mind that for the vast majority of parents, milk production is a hardy process. Until about 150 years ago, our species’ survival depended on it. Before the 1880s, there was no safe substitute for human milk, and many babies who were not nursed did not survive. If milk-making was so fragile and easily disrupted, the human race would not have thrived. For many parents, an effective antidote to these worries is the empowerment that comes with a basic understanding of milk-making dynamics and how their own actions affect milk production.

How Milk Production Works

After birth, many new families mistakenly believe that healthy milk production is either there or it’s not there. While some lactating parents are naturally bigger milk producers than others, the most influential factor in the volume of milk made is what parents (and babies) do or don’t do. And that’s a good thing. While not every challenge can be overcome, it can be reassuring to know that many strategies are available to both prevent and address milk-production issues.   

What dynamics are most important to know? “Drained glands make milk faster” is one critical dynamic. [2] The breasts consist in part of glands, where with stimulation milk is made. For the lion’s share of nursing parents, more milk removals per day, either by nursing or milk expression, is the key to healthy milk production. The more times each day the milk is removed and the more fully it’s removed, the faster milk is produced. That’s how parents of multiples produce enough milk for twins and triplets. (And they do!) We even have recorded cases of parents producing enough milk for quadruplets. [3] How do they do it? They nurse their babies around the clock whenever their little ones show feeding cues (rooting, hand-to-mouth, fussing). Very frequent nursing (or pumping) gives their body the signal to keep making milk faster.

The opposite is also true: “Full glands make milk slower.” When parents replace nursing or milk expression sessions with formula (or even expressed milk from their freezer stash), the milk that accumulates in their glands sends their body the signal to make milk slower. Many new parents are unaware that feeding formula without pumping can decrease their milk production. [4] Sadly, some families find that as they supplement with formula more and more and stimulate their glands less and less, milk production slows and more supplements are needed.   

It is also common during the early weeks for families unfamiliar with nursing norms to misinterpret their baby’s normal feeding behaviors. Because their baby wants to nurse again soon after feeding (nature’s way of stimulating faster milk production), they erroneously believe this is a sign they don’t have enough milk. Newborns often bunch their feeds together (“cluster nurse”) during some parts of the day. This does not mean milk production is low. (Whatever the baby’s behavior, the expected weight gain is proof positive of ample milk production.)

Nursing and Fertility

In addition to affecting rate of milk production, nursing frequency also affects fertility. Due to the hormones released when baby nurses, in general, more frequent nursing leads to longer periods of infertility after birth. But each person’s biochemistry is unique, so the effect of nursing on fertility varies from person to person.

What’s average? When parents exclusively nurse from birth, gradually introduce solid foods around 6 months, and continue night feeds, some estimate that on average return of the menses occurs at around 1 year. However, if the lactating parent is not directly nursing at all feeds (even if expressed milk is given), solids are introduced earlier than 6 months, or the baby does not nurse at night, earlier return of menses is likely. [5]

During the nearly 40 years I’ve helped nursing families, I’ve seen a range of experiences. Some exclusively nursing parents begin menstruating as early as 6 weeks after birth, while others (myself included) go as long as 2 years before their first post-birth period. When nursing intensity is similar, this variation in body response is due to individual differences in biochemistry. After 6 months, the more time that passes before the first period, the more likely it is that ovulation will occur before the menses begin. [6] This means, of course, that it is possible to become pregnant before the first period.

Dips in Milk Production During the Menstrual Cycle

Many parents do not experience slowed milk production during their menstrual cycle, so this is another example of individual differences. Keep in mind that sometimes the return of the menses is a symptom of fewer daily milk removals, which also causes a slowing of milk production. In other words, rather than the menses causing slowed milk production, nursing or pumping fewer times per day may be the root cause of both the period returning and slowed milk production.  

What are signs of a decrease in milk production? Definitely an unexpected slowing of the baby’s weight gain. Are there other signs? Yes, but these may have other causes. A baby who was happily going for hours between feeds may suddenly revert back to the feeding frenzies (cluster nursing) common in newborns. Baby may want to nurse again within a few minutes or even all evening. But other factors—such as teething pain and illness—may cause these behaviors, too. If the number of milk removals per day dropped within the last few weeks (is baby sleeping longer at night?), this may cause slowed milk production, too. The overlap of this behavior with the menstrual cycle is sometimes coincidental.

Boosting Milk Production

Should slowed milk production cause panic? No. It’s helpful to know that at an average nursing session, babies only take only about two thirds of the milk available in the gland. [2] Nursing longer, more often, or even continuously gives a baby access to lots more milk. (Nature builds in a milk reserve.) Just keep moving baby back and forth from side to side until he is done. Think of the glands as fountains continuously producing milk rather than a container that can be emptied. Responding to baby’s cues to feed more often or longer not only provides the baby with more milk; it also stimulates faster milk production, quickly returning it to its previous level. Most likely, within a couple of days, baby will return to his normal feeding pattern. Giving formula or previously pumped milk, on the other hand, does NOT send the body the signal to make milk faster. When in doubt, take baby for a weight check. With a healthy weight gain, ample milk production is a given. In this case, another cause is responsible for baby’s change in behavior.

What is it about the menstrual cycle that causes some parents to experience a small but temporary slowing of milk production? After ovulation, blood levels of estrogen and progesterone rise and calcium levels fall. [7] For some, higher estrogen levels are associated with decreased milk production, [8] but to have this effect,  estrogen levels usually need to be much higher than the levels measured after ovulation.   

For parents who experience a noticeable slowing of milk production related to their menstrual cycle, taking a calcium/magnesium supplement may help. U.S. lactation consultants Lisa Marasco and Diana West suggest this in their 2020 book for parents,  Making More Milk. [9] (Its comprehensive second edition describes what is currently known about every aspect of milk production.) Although at this writing we have no research on the impact of taking calcium/magnesium supplements on milk production during the menstrual cycle, some report good results. These authors suggest taking between 500 mg calcium/250 mg magnesium and 1000 mg calcium/500 mg magnesium starting 3 days before an expected period and continuing it for the first 3 days after bleeding begins. They say some see results within 24 hours. 

The key point to remember is that for most families, milk production is extremely resilient. By taking advantage of frequent nursing and/or milk expression, even if milk-making slows in the short term, baby can usually get the milk she needs by simply nursing longer and more often. With this extra stimulation, milk production usually quickly rebounds to previous levels.

References

1 Morrison, A.., Gentry, R., & Anderson, J. (2019). Mothers’ reasons for early breastfeeding cessation. MCN: American Journal of Maternal/Child Nursing, 44(6):325-330.

2 Kent, J. C. (2007). How breastfeeding works. Journal of Midwifery & Women’s Health, 52(6), 564-570.

3 Berlin, C. M. (2007). “Exclusive” breastfeeding of quadruplets. Breastfeeding Medicine, 2(2), 125-126.

4 DaMota, K., Banuelos, J., Goldbronn, J., et al. (2012). Maternal request for in-hospital supplementation of healthy breastfed infants among low-income women. Journal of Human Lactation, 28(4), 476-482.

5 Labbok, M. H. (2015). Postpartum sexuality and the Lactational Amenorrhea Method for contraception. Clinical Obstetrics and Gynecology, 58(4), 915-927.

6 Lewis, P. R., Brown, J. B., Renfree, M. B., et al. (1991). The resumption of ovulation and menstruation in a well-nourished population of women breastfeeding for an extended period of time. Fertility and Sterility, 55(3), 529-536.

7 Dullo P, Vedi N. (2008). Changes in serum calcium, magnesium and inorganic phosphorus levels during different phases of the menstrual cycle. Journal of Human Reproductive Sciences, 1(2):77-80.

8 Oladapo, O. T., & Fawole, B. (2012). Treatments for suppression of lactation. Cochrane Database of Systematic Reviews(9), CD005937. doi:10.1002/14651858. CD005937.pub3.

9 Marasco, L., & West, D. (2020). Making More Milk: The Breastfeeding Guide to Increasing Your Milk Production (2nd ed.). New York, NY: M