Study Evaluates Relationship Between Prenatal Employment, Adverse Birth Outcomes

April 25, 2013 — "Reevaluating the Relationship Between Prenatal Employment and Birth Outcomes: A Policy-Relevant Application of Propensity Score Matching," Kozhimannil et al., Women's Health Issues, March 2013.

"[C]haracterizing the influence of employment on childbirth-related health is relevant for families, employers, insurers, health care providers, and for the government and private sector systems that support the care and well-being of mothers and children," according to Katy Kozhimannil of the University of Minnesota School of Public Health and colleagues. About 67% of first-time mothers are employed during their pregnancies, with 87% working outside the home into their last trimester, the researchers noted.

Prior research on birth outcomes among employed pregnant women is "extensive" but methodologically limited. The researchers noted that it is "very difficult to disentangle a woman's employment choices from her birth outcomes given that both may be influenced by factors that are not easily measured or are unavailable in many data sets," such as financial stress or social support.

Their study aimed to isolate the potential causal impact of full-time, part-time or absence of employment during pregnancy.

Methods

The researchers used data from the Listening to Mothers series of surveys, which included English-speaking women ages 18 to 45 who gave birth to singletons at U.S. hospitals in 2005. The surveys were conducted via telephone or the Internet.

For their analysis, the researchers considered women working 30 or more hours per week to be employed full-time and those working fewer than 30 hours to be working part-time.

The researchers compared birth outcomes among women who were working full-time during pregnancy with those who were employed part-time, as well as with those who were not employed. They also compared outcomes among women who worked part-time during their pregnancies with those who did not work.

Results

There were 632 women who worked full-time, 250 working part-time and 616 who were not employed during their pregnancies, the researchers found. Nearly all of the women had some health insurance coverage for maternity care.

Eighty-four participants (5.6%) gave birth to a low-birthweight infant and 118 (7.9%) delivered preterm, or before 37 weeks of pregnancy.

The researchers found no differences in low birthweight or preterm birth outcomes based on employment status. However, other known risk factors, such as race, were "highly predictive of adverse outcomes," they wrote. Specifically, black women gave birth to infants that weighed an average of 329 grams less and were born about four days earlier than infants born to white women.

Discussion

"Whether a woman is employed full time does not significantly affect her birth outcomes," the researchers wrote, adding, "Although employment is itself not causally linked with adverse birth outcomes, workplace policy ought to be a target of policy efforts, because many known risk markers occur with greater frequency among employed women."

The findings regarding race and birth outcomes are consistent with prior research, Kozhimannil and colleagues noted, adding that their analysis demonstrated "that this race effect is independent of employment status." They wrote, "Continued policy and research efforts are warranted to explore and eliminate the causes of this disparity."

Conclusions

The researchers suggested that "[f]uture efforts to address the persistent problems of low birth weight and preterm births should focus on the characteristics of women (including characteristics related to their jobs) that put them at risk of adverse birth outcomes."

Additional "research may inform employer, insurer, and clinical policies as well as programmatic efforts to improve the health and well-being of employed mothers and their infants and to reduce persistent racial and ethnic disparities in birth outcomes," the researchers concluded.