The World Health Organization recommends that newborn children be breastfed exclusively for the first six months of their lives, with continued partial breastfeeding for up to two years. In the U.S., the American Academy of Pediatrics also recommends six months of exclusive breastfeeding, and at least 12 months of complementary breastfeeding. And yet for all of this, few women anywhere in the industrialized world ever come close to meeting those recommendations — and they often cite a common problem: They can’t produce enough breast milk.
Past research has suggested that in many cases, the problem may simply be one of perception — particularly among women who don’t fully understand normal lactation. In other instances, technical difficulties with breastfeeding may also contribute to the sense that not enough milk is being produced. But other factors have also been implicated. A series of studies from the Cincinnati Children’s Hospital Medical Center, for example, have shown links between diabetes — an increasingly common disease — and low breastmilk production.
The bottom line: There is still a great deal that researchers don’t understand about this most basic human activity and the problems many women may be experiencing.
“Lactation is the last bastion of women’s health that we’re still really screwing up,” said Alison Stuebe, an OB-GYN at the University of North Carolina School of Medicine. “We don’t know much about breast function. When a woman experiences trouble breastfeeding, there’s no battery of tests to figure out why it’s happening. She’s often told to try harder.”
While definitive research into the issue is lacking, two recent studies — one conducted in Denmark, and another in the United States — have attempted to uncover environmental factors that might contribute to low milk production. Both studies focused on perfluorinated compounds (PFCs), a large group of chemicals used in the manufacture of everything from nonstick cookware and camping gear to carpets, food wrappers, and firefighting foams.
Along with her colleagues, Amalie Timmermann, a research assistant in the Department of Environmental Medicine at the University of Southern Denmark, assessed 1,130 women from two birth cohorts in the Faroe Islands, a Danish archipelago in the North Atlantic. The researchers measured the levels of PFC chemicals in each mother’s blood. For some mothers they took measurements late in pregnancy, for others they measured levels shortly after they gave birth.
Women with the highest levels of one PFC called perfluorooctane sulfonic acid (PFOS) in their blood stopped breastfeeding almost one-and-a-half months earlier than women with the lowest levels of the chemical. Women with higher levels of another PFC called perfluorooctanoic acid (PFOA) stopped exclusive breastfeeding about 15 days earlier. Exclusive breastfeeding meant that the infants received only breast milk or water, but no other foods during that time. Many mothers continue to breastfeed for some time after introducing formula or other foods. The study was published in July in the journal Reproductive Toxicology.
On average, the Faroese study women breastfed exclusively for five months and continued some breastfeeding for a total of nine months. Their PFC exposures were comparable to average levels of the chemicals found in people in the U.S. and Europe, Timmermann said.
The U.S. study, led by Brown University researchers, looked at 336 women who gave birth at Cincinnati, Ohio area hospitals. Many had unusually high PFC levels, because their homes were located downstream from a major chemical plant. Rather than calculating how much sooner mothers with high PFC levels stopped breastfeeding like the Danish researchers did, the U.S. group looked at how much more likely women with high PFC levels were to stop breastfeeding by certain benchmark points. They found that women with the highest blood levels of PFOA were 77 percent more likely to completely stop breastfeeding by three months, and 41 percent more likely to completely stop breastfeeding by six months than women with the lowest PFOA levels. The study was published in May in Environmental Research.
The women in the Cincinnati study had roughly twice the levels of PFOA in their bodies as most Americans, according to the study’s authors. The Cincinnati women also spent far less time breastfeeding, on average, than their Faroese counterparts. Most women in the Cincinnati study breastfed exclusively for less than one month. Their average total time spent breastfeeding was about six months.
In both studies, the researchers controlled for other factors known to influence breastfeeding practices, including race or ethnicity, education level, and prior breastfeeding experience.
Megan Romano, an epidemiologist at Dartmouth College who led the U.S. study while she was at Brown University, suggested the relationship was clear. “Taken together, these studies show a link between greater exposure to these substances and shorter duration of breastfeeding,” she said, “though it may vary from population to population which [PFC] exposure is most important.”
But it’s also possible that PFC exposure isn’t really involved at all, and these early correlations are merely that — a point that the researchers themselves conceded. Stuebe noted that a host of social factors — from inadequate support from healthcare providers and insufficient maternity leave, to a lack of privacy at work for pumping — can influence a woman’s decision to stop breastfeeding. And it’s also possible that some unmeasured environmental exposure could be behind the association.
Until more research is focused on the underlying physiology of breastfeeding, including the influence of various environmental factors on breastfeeding mothers, the mystery will likely continue.
“Clearly more research is needed to identify specific practices or environmental exposures that are disrupting physiology,” Stuebe said, “and making it harder than evolution would have intended to breastfeed.”