April 26, 2021

Kaiser Permanente analysis finds managing weight, diet, and stress reduces risk of premature delivery

A combination of 3 healthy lifestyle factors is associated with a 70% lower risk of preterm birth, according to an analysis of data from a Kaiser Permanente study involving nearly 2,500 pregnant women in Northern California.

In the study, women whose weight early in pregnancy was within recommended parameters, who ate a healthful diet, and who had stress at low to moderate levels were 70% less likely than women without any of those lifestyle factors to have an early birth. The findings were published April 26 in The American Journal of Clinical Nutrition.

photo of Yeyi Zhu, PhD

Yeyi Zhu, PhD

“These findings highlight the importance of an overall healthy lifestyle versus focusing on individual risk factors,“ said lead author Yeyi Zhu, PhD, a research scientist with the Kaiser Permanente Division of Research. “Multiple prenatal factors influence one another and are difficult to disentangle. We hope this combination approach produces useful information for women and their doctors.”

Preterm birth takes place before 37 weeks gestation and is the second-leading cause of neonatal mortality in the United States. Risk factors for preterm birth include genetic traits, medical conditions, and lifestyle factors. This study focused on lifestyle factors that were potentially modifiable.

The researchers examined data from 2,449 women enrolled between 2013 and 2017 in the Pregnancy Environment and Lifestyle Study, known as PETALS, which tracked health, environmental, and lifestyle factors through pregnancy. Women reported information about both their current status during pregnancy and previous, prepregnancy lifestyle. The researchers also had information from the women’s electronic health records about lifestyle factors in the year prior to conception.

photo of Mara Greenberg, MD

Mara Greenberg, MD

Women whose weight, diet, and stress were in healthy ranges had lower risk of preterm birth than women who did not have those factors in healthy ranges. The difference in risk increased with the number of healthy lifestyle factors: 70% lower risk with healthy weight, diet, and stress levels; 51% lower with 2 of these factors; and 38% lower with 1 factor.

“Overall, this is a call for investing in women’s health over their lifespans, not just during pregnancy, which can be considered a societal responsibility as well as a capability of large integrated health care organizations such as ours,” said Mara Greenberg, MD, a maternal-fetal medicine specialist with The Permanente Medical Group and perinatal clinical and research director with the Kaiser Permanente Regional Perinatal Service Center. “Such an investment also stands to reduce well-described disparities in preterm birth.”

Focus on preconception, early pregnancy

The study focused on the period before pregnancy and on its first 12 weeks. Nearly 1 in 10 women in the sample had all 3 modifiable low-risk factors in healthy ranges. Of the 2,449 women in the study, 160 (6.5%) delivered early (before 37 weeks), similar to the prevalence in California at the time. Women who delivered preterm were more likely to be older; self-identify as African American, Asian, or Pacific Islander; have obesity before pregnancy; or have a history of hypertension or depression.

Along with examining the roles of weight, diet, and stress, the researchers also considered factors such as smoking, drinking alcohol, and moderate-to-vigorous physical activity and did not find significant associations with preterm birth. However, they also noted the women in this study reported lower smoking and alcohol use rates than is typical of pregnant women in the United States.

Other research on lifestyle factors and preterm birth risk has largely focused on each individual factor, and results have been mixed. The authors said this analysis is different because it grouped healthy lifestyle factors together and focused on both early pregnancy and preconception, when women can take action to increase the chances of a full-term delivery. “Our findings suggest patients may benefit from a broad healthy lifestyle prevention approach that includes weight management, dietary quality, and psychological health during preconception and early pregnancy,” said senior author Assiamira Ferrara, MD, PhD, senior research scientist with the Division of Research.

While the results suggest women can influence their risk of preterm birth by addressing their weight, diet, and stress before and during early pregnancy, they should also be aware of other factors under their control, such as avoiding alcohol and smoking, the authors said.

The researchers said the analysis was strengthened by using data for a relatively large number of women of diverse racial and ethnic backgrounds. Ferrara and her colleagues are now following the children of women from the PETALS study through the ECHO program (or Environmental influences on Child Health Outcomes), a National Institutes of Health initiative including 50,000 children. The project will assess whether a mother’s healthy lifestyle during pregnancy may reduce the long-term consequences for a child born prematurely, such as impaired neurodevelopment and growth.

The study was funded by the National Institute of Environmental Health Sciences and the ECHO program, National Institutes of Health, Office of the Director.

Other co-authors were Monique M. Hedderson, PhDSylvia E. Badon, PhD; Juanran Feng, MS; and Charles Quesenberry, PhD, all of the Division of Research.