SMFM 2016 Poster Presentation

Nicholson, James M., Lisa C. Kellar, Serdar H. Ural and Jerome L. Yaklic (2016). “Increases in the Rates of Term Stillbirth in the USA Following the Adoption of the 39-Week Rule: When are the Additional Stillbirths Occurring?” Poster presented at the Society for Maternal-Fetal Medicine’s 36th Annual Pregnancy Meeting 2016 (SMFM 2016), Atlanta, GA, USA, 5 February 2016.

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ABSTRACT

Objective
Observational studies have identified associations between early-term delivery, as compared to full-term delivery, and various neonatal morbidities. As a result, an obstetric guideline called “the 39-week rule” was implemented throughout the USA in 2010. The rule restricts “non-indicated” planned delivery prior to 39 weeks of gestation and thereby increases the likelihood that deliveries occur during or after the 39th week of gestation. However, there is a known link between increasing gestational age and increasing cumulative risk of term stillbirth, and the USA rate of term stillbirth has increased since the implementation of the 39-week rule. This study sought to determine the gestational age pattern behind the increase in term stillbirth rate.

Study Design
Sequential ecological study over a 7-year period, using state data. Patterns of the timing of term birth, overall yearly stillbirth rate, and changes in the rate-proportion for each week of the term period over the 7-year period were the metrics of interest.

Results
Usable datasets were obtained from 46 states. Between 2007 and 2013 in the USA, the proportion of term births occurring before the 39th week of gestation decreased (Figure 1) and the overall rate of term stillbirth increased (Figure 2). The increase in the incidence of term stillbirth appeared to occur primarily in the 37th, 38th and 39th weeks of gestation (Figure 3).

Conclusion
Despite a reduction in the proportion of term births that occurred in the 37th and 38th weeks of gestation the burden of term stillbirth gestation, grew among early-term deliveries. The burden of term stillbirth also increased within the 39th week of gestation. Hence, the increase in the burden of term stillbirth appears to have increased primarily within the gestational ages that were most directly impacted by the 39-week rule. This study raises the possibility that the 39-week rule may be causing serious unintended harm. Additional studies measuring the possible impact of the implementation of the 39-week rule on major childbirth outcomes are urgently needed.

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