Early Planned Birth Tied to Greater Risk for Poor Development

Ricki Lewis, PhD

November 07, 2016

Planned birth before 39 weeks' gestation increases risk for poor child development at school age, according to a population-based study published online November 7 and in the December 2016 issue of Pediatrics.

"We found not only that the risk of poor development increased for every additional week a child is born before 39 to 40 weeks' gestation but that it increased more for modes of birth other than vaginal birth after the spontaneous labor, even among women whose pregnancies we were able to identify as being low risk," the researchers write. They suggest that delaying birth for even a week can have significant long-term benefits.

Labor induction and prelabor cesarean section have often been done for nonmedical reasons, including convenience to either patient or physician. Several studies indicate a steady increase in planned births and decrease in overall gestational age from 40 to 39 weeks internationally. However, because development of the fetal brain accelerates after the 32nd week until full term, delivery before 39 weeks could prevent a child from attaining neurodevelopmental potential.

Jason P. Bentley, MBiostat, from the University of Sydney, Australia, and colleagues probed the association between early child development and gestational age at birth, as well as the mode of birth. They considered 153,730 children born in New South Wales between 2002 and 2007 who had undergone school-age assessment using the 100-item Australian Early Development Census.

The authors used linked birth records to determine gestational age at birth and mode of birth. The average age at assessment was 5.5 years.

The authors examined five domains of development: physical health and well-being, language and cognition, social competence, emotional maturity, and general knowledge and communication. Children scoring in the lowest 10% were classified as "developmentally vulnerable" for that domain, and if they fell below the lowest 10% in 2 or more domains, they were considered to be "developmentally high risk" (DHR), which was the primary outcome.

Planned births accounted for 41.4% of the total. That percentage rose to 48.4% of births at 37 weeks and 55.2% at 38 weeks. Overall, 5.6% of the infants were born at 32 to 36 weeks, and 22.5% were born at 37 to 38 weeks.

The researchers found that 9.6% of the children were DHR. These children were more likely to be boys or small for gestational age or had mothers who were younger, were socioeconomically distressed, and smoked during pregnancy.

The risk for DHR decreased with increasing gestational age at delivery, after adjusting for maternal and socioeconomic factors, small for gestational age, age at assessment, and sex.

Specifically, compared with delivery at 40 weeks, the adjusted relative risk (aRR) for DHR was 1.25 (95% confidence interval [CI], 1.08 - 1.44) for 32 to 33 weeks, 1.26 (95% CI, 1.18 - 1.34) for 34 to 36 weeks, 1.17 (95% CI, 1.10 - 1.25) for 37 weeks, 1.06 (95% CI, 1.01 - 1.10) for 38 weeks, 0.98 (95% CI, 0.94 - 1.02) for 39 weeks, and 0.99 (95% CI, 0.94 - 1.03) for 41 or more weeks.

Moreover, when the investigators stratified according to mode of birth, they found that the risk for DHR was elevated after labor induction or prelabor cesarean delivery (aRR, 1.07, 95% CI, 1.04 - 1.12) compared with vaginal birth after spontaneous labor.

Further, the team found that the risks associated with planned delivery and early birth were additive, such that a planned birth at 37 weeks was associated with 26% greater risk for DHR (aRR, 1.26; 95% CI, 1.18 - 1.34) compared with spontaneous labor and vaginal delivery at 40 weeks. Planned delivery at 38 weeks was associated with a 13% increase in relative risk (aRR, 1.13; 95% CI, 1.08 - 1.19).

"[T]he case for avoiding elective or planned delivery before 39 weeks is strong, and getting stronger with data such as that presented by Bentley et al," write Siobhan M. Dolan, MD, MPH, and Mary L. Rosser, MD, PhD, from the Department of Obstetrics & Gynecology and Women's Health at Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, New York, in an accompanying editorial.

Eliminating the practice of planned deliveries will require efforts on multiple fronts, including quality improvement efforts, public education campaigns, and relabelling 37 0/7 to 38 6/7 weeks as early term vs 39 0/7 to 40 6/7 as full term.

"Equally important is that obstetricians and pediatricians provide a unified message to women and families that the optimal timing of planned delivery is at least 39 weeks," they conclude.

Limitations of the study include reliance on medical records and the inability to account for all potential confounding factors.

The researchers and editorial contributors have disclosed no relevant financial relationships.

Pediatrics. Published online November 7, 2016. Abstract

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