Importance: Birth at 39 weeks' gestation is common and thought to be safe for mother and neonate. However, findings of long-term outcomes for children born at this gestational age have been conflicting.
Objective: To evaluate the association of birth at 39 weeks' gestation with childhood numeracy and literacy scores at ages 7 to 9 years compared with birth at 40 to 42 weeks' gestation.
Design, setting, and participants: In this Australian statewide, population-based cohort study using a causal inference framework based on target trial emulation, perinatal data on births between January 1, 2005, and December 31, 2011, were linked to educational outcomes at 7 to 9 years of age. Statistical analyses were performed from December 2022 to June 2023.
Exposure: Birth at 39 weeks' gestation compared with birth at 40 to 42 weeks' gestation.
Main outcomes and measures: Numeracy and literacy outcomes were assessed at 7 to 9 years of age using Australian National Assessment Program-Literacy and Numeracy data and defined by overall z score across 5 domains (grammar and punctuation, reading, writing, spelling, and numeracy). Multiple imputation and doubly robust inverse probability weighted regression adjustment were used to estimate population average causal effects.
Results: The study population included 155 575 children. Of these children, 49 456 (31.8%; 24 952 boys [50.5%]) were born at 39 weeks' gestation and were compared with 106 119 (68.2%; 52 083 boys [49.1%]) born at 40 to 42 weeks' gestation. Birth at 39 weeks' gestation was not associated with altered educational outcomes for children aged 7 to 9 years compared with their peers born at 40 to 42 weeks' gestation (mean [SE] z score, 0.0008 [0.0019] vs -0.0031 [0.0038]; adjusted risk difference, -0.004 [95% CI, -0.015 to 0.007]). Each educational domain was investigated, and no significant difference was found in grammar and punctuation (risk difference [RD], -0.006 [95% CI, -0.016 to 0.005]), numeracy (RD, -0.009 [95% CI, -0.020 to 0.001]), spelling (RD, 0.001 [95% CI, -0.011 to 0.0013]), reading (RD, -0.008 [95% CI, -0.019 to 0.003]), or writing (RD, 0.006 [95% CI, -0.005 to 0.016]) scores for children born at 39 weeks' gestation compared with those born at 40 to 42 weeks' gestation. Birth at 39 weeks' gestation also did not increase the risk of scoring below national minimum standards in any of the 5 tested domains.
Conclusions and relevance: Using data from a statewide linkage study to emulate the results of a target randomized clinical trial, this study suggests that there is no evidence of an association of birth at 39 weeks' gestation with numeracy and literacy outcomes for children aged 7 to 9 years.