Women living in rural counties more likely to deliver before 39 weeks’ gestation

Pregnant women living in rural counties of the United States were more likely to deliver before 39 weeks’ gestation compared with those living in non-rural counties, according to a retrospective cohort study.

The data, which were published in the American Journal of Obstetrics & Gynecology, also showed that women in rural counties were less likely to give birth between 39 and 41 weeks’ gestation.

“National safety and quality efforts have aimed to optimize delivery timing at 39 weeks,” Osinakachukwu Mbata, MD, an OB/GYN resident at the Oregon Health & Science University School of Medicine in Portland, Oregon, and colleagues wrote. “The 39-week rule was the result of evidence suggesting reduced neonatal morbidity and mortality with delivery at 39 weeks or beyond when compared to deliveries in the early term period (defined as 37 weeks, 0 days to 38 weeks, 6 days). Studies show broad compliance with this effort nationally; however, it is unclear if differences in compliance to the 39-week rule exist for rural women.”

Mbata and colleagues used restricted use, linked vital statistics-infant death data from the National Center of Health Statistics, as well as data on maternal county of residence and the county of the delivery hospital, to create a cohort of low-risk, singleton pregnancies.

Overall, the researchers identified 3,010,183 women who met the inclusion criteria. Of these, 338,093 (11.2%) lived in a rural county.

A greater proportion of women with a rural residence vs. those living in non-rural counties gave birth at 36 weeks (3.2% vs. 2.9%), 37 weeks (7.9% vs. 7.6%) and 38 weeks (16.2% vs. 16.1%; all, P < .001). The relative risk ratio for delivery at 36 weeks vs. 39 weeks was 1.03 for women residing in rural counties (95% CI, 1-1.05).

Conversely, a smaller proportion of women living in a rural county delivered at 39 weeks’ gestation to 41 weeks’ gestation compared with their counterparts (72.7% vs. 73.4%; P < .001). The relative risk ratio for delivery at 40 weeks vs. 39 weeks was 0.83 for women living in rural counties (95% CI, 0.82-0.84).

“It is unclear if these differences are the result of medical necessity, differences in timing of spontaneous delivery or variance in application of the 39-week rule,” Mbata and colleagues concluded. “Additional research is needed to identify the source of these differences and any associated adverse effect is warranted.”