Women who breastfeed for at least five months have more kids

In "Intensive Parenting: Fertility and Breastfeeding Duration in the United States," published in the journal Demography, Cornell University professor of sociology Vida Maralani, with Hunter College professor Samuel Stabler, reports that women who initiate breastfeeding did not differ in how many children they expected to have before they started their families. Rather, the number of children women actually bear differs by how long they breastfeed their first child. Women who breastfeed for shorter durations are more likely to have fewer children than they expected, while women who breastfeed longer are as likely to achieve their expectations as to exceed them.

The researchers caution that their results do not imply that breastfeeding duration causes women to have larger families. They write, "Our study reveals the opposite: the interconnectedness of family preferences and child investment across the life course." But they do find that many factors, such as differences in education, marital status, family income, and working for pay do not explain these patterns. The authors point to the need to study other potential explanations such as spousal support, preferences for time spent with children or work flexibility.

"Breastfeeding is a time-intensive and culturally and emotionally charged topic in the U.S. with many different stakeholders," said Maralani. "Women hear the strong message that they should breastfeed their infants for the first year of life, yet it is unambiguously clear that they find these guidelines difficult to follow in practice."

The researchers used a nationally representative longitudinal dataset, from 1979 to 2012, which provides information on a cohort of nearly 3,700 mothers. They measured women's expected fertility at least one year before women conceived their first child to examine the link between their expectations of future fertility and actual behavior. These data also enabled the authors to account for differences in breastfeeding and fertility by education, age, marital status, family income and work histories.

Maralani and Stabler's findings are in stark contrast to established research that shows highly educated Americans are more likely to have fewer children than they expected. Instead, the researchers write, "long-duration breastfeeding serves as a proxy for identifying a group of very highly educated women who seem to achieve and exceed their expected fertility, suggesting that breastfeeding duration may capture numerous observed and unobserved preferences about family and child investment, and necessarily, the tradeoffs that women and couples make."