A new Mater Research study suggests that birth at 39 – 40 weeks' gestation is associated with significantly reduced risks of adverse outcomes for babies.
Led by Professor Sailesh Kumar and funded by the National Health and Medical Research Council and Mater Foundation, the study investigated the outcomes of 472,520 ‘low-risk’ single-baby pregnancies in Queensland between 2000 and 2021.
The research team compared the outcomes of ‘planned’ births (involving either induced labour or c-sections) in the 39th week of pregnancy with births in which the pregnancy progressed beyond 40 weeks without intervention.
The study found that planned birth was associated with 52 per cent lower odds of perinatal mortality (stillbirth or neonatal death) and significant reductions in the risk of severe neurological and non-neurological complications in the baby after birth.
Prof Kumar, senior Maternal Fetal Medicine specialist at Brisbane’s Mater Mothers’ Hospitals, and Dr Kylie Crawford, epidemiologist at Mater Research, said the study’s findings were supported by previous research, but cautioned that further randomised trials on the timing and methods of planned birth were needed.
“The finding of this very large observational study was that planned birth at this stage of pregnancy is associated with better perinatal and maternal outcomes,” Prof Kumar said.
“However, these results should not be taken as unqualified support for routinely offering planned birth, particularly by c-section, in the 39th week.”
Prof Kumar said further evidence was required before changes to clinical practices should be recommended.
Regardless of mode of birth, infants born at early-term gestation (in the 37th and 38th week) are known to face higher risks of both short-term complications (such as breathing difficulties and admission to neonatal intensive care) and longer-term complications (such as behavioural problems).
The risks of neonatal and maternal adverse outcomes are also higher when birth occurs at 40+ and 41+ weeks, compared to 39 weeks’ gestation.
Professor Kumar said birth at very prolonged gestations should be avoided whenever possible.
The full paper, titled Perinatal mortality and other severe adverse outcomes following planned birth at 39 weeks versus expectant management in low-risk women: a population-based cohort study was published in The Lancet EClinicalMedicine in February 2025.
