A Multi-State Analysis of Early-Term Delivery Trends and the Association With Term Stillbirth Trends in Stillbirth by Gestational Age in the United States, 2006–2012 Stillbirth and the 39-Week Rule: Can We Be Reassured?

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We wish to express concern about the collection of articles suggesting that the 39-week rule has not increased the rate of U.S. term stillbirth.1–3 The 39-week rule has definitely increased the gestational age at delivery for a significant proportion of U.S. term deliveries1; an association is known to exist between increasing gestational age at term and increasing prospective risk of stillbirth.4 It would seem logical to expect that the application of the 39-week rule should lead to at least some increase in the rate of term stillbirth.4 Are these articles adequately reassuring?Little et al1 analyzed a U.S. dataset that encompassed term singleton births between 2005 and 2011. The 39-week rule was not widely enforced until 2010; therefore, this study includes just one postcodification year and likely does not adequately reflect the 39-week rule's actual effects. In addition, this article does not report the decrease in the proportion of term pregnancies that delivered during or after the 40th week of gestation during the study period. This actual trend would be expected to decrease the incidence of late-term stillbirth, which would both reduce the overall rate of term stillbirth and obscure the actual effects of the 39-week rule.MacDorman et al2 report that the prospective risk of term stillbirth as a function of gestational age did not change between 2006 and 2012. However, the overall yearly rate of term stillbirth is based on both strata-specific rates and the distribution of populations among the various strata. If the 39-week-rule moved a significant proportion of deliveries to higher-risk strata, then—all else being equal—that shift should have caused an increase in the overall rate of term stillbirth.Although the editorial by Bailit and Lappen3 clearly states that “further research is needed,” their main message was one of reassurance. However, before a medical practice is implemented, it is important to be sure that it is not harmful (primum non nocere). For the 39-week rule, that criteria has not yet been met. Until high-quality research can show that the 39-week rule actually provides more benefit than harm, its enforced use should be reconsidered.

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