We thank Dr Hill for his interest in our article that reported an association between the adoption of the 39-week rule and a significant increase in the rate of term stillbirth in the United States from 2007 through 2013.
Dr Hill questions our primary finding based on his claim that our data set was not complete and that a recently published article concluded that the recent increases noted in rates of US term stillbirth were not statistically significant. We are puzzled by Dr Hill’s outright dismissal of our findings. The data used in our article were impartially provided by 45 states and the District of Columbia and our final data set contained information on >86% of term deliveries (ie, >21 million deliveries) that occurred in the United States during the time the 39-week rule was adopted. In contrast, the article cited by Dr Hill did not include any data from 2012 through 2013 in its analysis. This is a significant deficiency because progressive changes in the timing of term childbirth were continuing to occur in 2012 through 2013, and these changes were the direct result of the 39-week rule. The full impact of the 39-week rule on term stillbirth rates is therefore not adequately assessed by the article cited by Dr Hill. A different study cited by Dr Hill actually supports rather than challenges our findings.
At the heart of this issue is the question: Does the 39-week rule represent an optimal management approach to term pregnancy? Dr Hill states that it does, and recommends that the strict application of the rule to low-risk pregnancies should continue until further research is done. We remain steadfast in our belief that rates of US term stillbirth have increased and we agree with others that the use of the 39-week rule may increase term stillbirth rates. We are also aware that the rate of term neonate neonatal intensive care unit admission increased from 2007 through 2013, and that no large study exists that reports statistically significant associations between the adoption of the 39-week rule and improvements in rates of any important childbirth outcome. Given evidence of possible harm, and given the lack of evidence of actual benefit, we believe it is our duty to question the wisdom of the strict use of this overly simplistic rule. For many pregnancies–including some currently considered low-risk–the optimal time of delivery is most likely <39 weeks.