Last updated: Mar 02, 2016
My daughter came out of the womb hungry. Now 10 months old, she happily nurses six times a day. We both thrive on the wonderful intimacy of our nursing relationship. But this relationship may be preventing her from becoming a big sister.


Regular nursing sessions can lessen a woman's fertility. Although it is a nice idea to allow a woman's body time to rest between pregnancies, this can create a real conflict when that woman, like me, is almost 39.

I am part of a relatively new subset of nursing mothers—those whose age necessitates closer-than-ideal spacing between births. Every woman's body is different; some can continue nursing on demand and conceive, while others need to wean completely before they ovulate again. So how do we balance the needs of a current infant against the desire for another child?

Wendy Haldeman, RN, an international board-certified lactation consultant, and one of the founders of the L.A.-based breast-feeding support center The Pump Station, faces this question frequently, as most of her clients are older than 35.

Haldeman encourages mothers to exclusively breast-feed for the first six months, and then, if need be, wean all night feedings. "Often, if moms have a regular 12-hour stretch without suckling, they will ovulate. If not, they have to continue to reduce the number of feedings until they do ovulate." But some moms, she notes, have to wean completely before they are able to ovulate.

How does breast-feeding stave off ovulation?
Although there isn't one clear answer, it seems that high prolactin (the hormone that causes lactation) levels have a lot to do with the continued suspension of ovulation.

Dr. Pamela Berens, MD, an associate professor of obstetrics, gynecology, and reproductive sciences at the University of Texas Health Science Center, at Houston, who researches lactation and breast milk, explained how prolactin levels fluctuate and affect reproductive functioning.

"Baseline prolactin levels typically fall after delivery, and by 2–3 months postpartum, the basal levels are about 40%–50% of initial levels," Dr. Berens says. "Even though the basal level may have dropped, it still roughly doubles with each nursing."

She says that the fall in the basal level is somewhat related to how often you breast-feed, but the pattern and level of prolactin do not accurately predict when your fertility will return.

According to Dr. Berens, prolactin inhibits the normal release of gonadotropin-releasing hormone (GnRH). GnRH is responsible for the release of two hormones—luteinizing hormone (LH) and follicle-stimulating hormone (FSH)—that are crucial to stimulating ovulation. And to make matters worse, when your ovaries are exposed to higher levels of prolactin, the follicles in the ovary do not develop properly.




Am I fertile yet?
Knowing when you're ovulating isn't as simple as having a period—it isn't unusual to menstruate without actually ovulating while breast-feeding. My ob-gyn suggested that I test my LH levels throughout a cycle to make sure that I am actually ovulating, even though I have a regular period.

If I have no LH surge, yet wanted to conceive, I would need to knock out some of my baby's feedings in order to kick-start ovulation.

And therein lies the quandary—do I do what's best for this baby, or some future hypothetical child? (Especially when a recent study found that each year, more than 900 preventable child deaths occur in the United States because most mothers don't follow the six-month breast-feeding recommendation.)

I could hope to join the ranks of the many women who have conceived while breast-feeding. According to a 1993 study published by the World Health Organization, a woman with a child younger than six months, who hasn't had her period return, and is fully or nearly fully breast-feeding has a 2% chance of getting pregnant. But if any of these three criteria are not met, a woman's chance of pregnancy begins to increase.

In my community alone there are dozens of women who can point to the children they conceived while breast-feeding; they were surprised by closely spaced children after they believed that breast-feeding was an effective form of birth control.

But it's a different story for the women who have had reproductive dramas in their family-building efforts, and, like me, are approaching the end of their fertile years. We face a difficult decision between breast-feeding and fertility.