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Delivering Late-term Babies: Is Later Better? :

July 12, 2021

When is the optimal time to deliver a full-term infant?

When is the optimal time to deliver a full-term infant? The thinking on this has changed over the years, as more data have come out. For instance, anywhere between 37 and 42 weeks was acceptable for a long time. Then, because of concerns about immature development for the early term infants and because of concerns about macrosomia and meconium aspiration for the late term infants, the sweet spot for delivering an infant seems to be between 39 and 40 weeks. It is rare when I see a baby who was born past 40 weeks’ gestation. But do we have that right?

Dr. Amanda Hedges and colleagues at Rutgers University and Princeton University looked at educational outcomes at age 9 years for infants who were born between 37 and 41 weeks’ gestation. The article describing their findings is being early released this week in Pediatrics. (10.1542/peds.2020-021287)

The authors analyzed data from the Fragile Families and Child Wellbeing study, a national cohort study that recruited infants born in 75 urban hospitals. The children were followed longitudinally, and when the children were 9 years old, the researchers requested permission to interview each child’s teachers. They asked the teacher to rate the child’s academic skills, in comparison to other children, in math, science and social studies, and language and literacy.

The authors found that children who were born at 39-40 weeks’ gestation were rated higher in academic performance than those who were born at 37-38 weeks’ gestation. However, the surprising result is that children who were born at 41 weeks’ gestation were rated higher than those born at 39-40 week’s gestation!

The authors provide possible explanations for this finding, related to ongoing synaptogenesis during the last few weeks of gestation.

Two obstetricians, Dr. Whitney Lieb and Dr. Siobhan Dolan from Icahn School of Medicine at Mount Sinai, in an accompanying commentary (10.1542/peds.2021-051427), note that many of the children in this study were from minority and low-income families. Could the timing of delivery possibly contribute to a reduction in disparities? They believe that these findings are important and must be considered by obstetricians when considering the optimal timing for birth.

Certainly, a single study may not be sufficient to change consensus about the best time to deliver an infant, but I would not be surprised if we see a shift towards later births as obstetricians and pediatricians consider findings such as these.

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