Woman’s health, education and marital status pre-pregnancy affect birth weight of her daughters, granddaughters

"We know that low-birth-weight babies are more susceptible to later physical and cognitive difficulties and that these difficulties can sharpen the social divide in the U.S. But knowing more about what causes low birth weight can help alleviate the intergenerational perpetuation of social inequality through poor infant health," said Kane, formerly a postdoctoral scholar at The University of North Carolina at Chapel Hill, where the research was conducted. She joined UCI in July.

Published in the June issue of the Journal of Health and Social Behavior, the study is based on both the National Longitudinal Survey of Youth 1979 and the Children of the National Longitudinal Survey of Youth 1979. The former yielded birth weights and pre-pregnancy physical and social health data on female respondents as well as social data on their mothers, while the latter captured this data on the previous survey participants' daughters. In total, Kane looked at 1,580 mother-daughter pairs, focusing on their weight at birth, marital status and education level.

"The odds of having a low-birth-weight baby were one and a half to two times greater for mothers who themselves were born low birth weight compared to mothers who were not born low birth weight," she said. "But also important are social factors, including education and marital status. Putting all of these factors -- both intergenerational and intragenerational -- together in a single model can tell us even more."

For example, education level pre-pregnancy can be transmitted from mothers to daughters across at least three generations, and this intergenerational transmission appears to affect birth weight of future generations, Kane said.

"And knowing that biological factors perpetuate the cycle -- being a low-birth-weight baby makes a woman more susceptible to delivering the same -- we start to see that we can't look at these two factors separately," she said.

This means that causes of low birth weight extend much further back than the time frame that's typically focused on: pregnancy. Kane's work shows that key factors can be traced to the mother's own early life experiences, in addition to factors dating back multiple generations.

"This really makes a difference in how we think about planning future population-level policies or programs that intend to reduce social inequalities in birth weight," she said.