Have gestational diabetes? Timing of delivery matters

Maternal-fetal specialists pinpoint which week is safest for baby

Dr. Nir Melamed with his patient Cherrylou Bautista. Melamed is a clinician-scientist specializing in maternal-fetal medicine at Sunnybrook Research Institute.

Photo: Nation Wong

Gestational diabetes affects up to 15%–20% of pregnant women. It is often clinical practice to induce labour in these cases at 38 or 39 weeks to decrease complications that include cesarean delivery, birth trauma and shoulder dystocia, a severe obstetrical emergency, whereby, after delivery of the head, the anterior shoulder of the infant gets stuck against the woman’s pubic bone. This condition can lead to nerve injury and paralysis of the arm, as well as fetal asphyxia and death. Doctors are not sure, however, whether inducing labour actually improves outcomes because only a few studies with small sample sizes have looked at the issue.

This lack of clarity led Dr. Nir Melamed, a clinician-scientist in the Women & Babies Research Program at Sunnybrook Research Institute (SRI) to investigate.

“The purpose was to determine whether routine induction of labour at 38 or 39 weeks can decrease the risk of cesarean section and improve the baby’s outcomes,” says Melamed. “The rationale is that gestational diabetes can lead to accelerated growth of a baby who might be exposed to high levels of glucose and insulin.” A large infant increases the risk of serious complications, he notes.

Melamed led the study using data from the Better Outcomes Registry & Network Ontario, or BORN, a registry of all births in Ontario. He looked at 14,600 women with gestational diabetes who delivered babies between April 2012 and March 2014.

He and his colleagues compared the outcomes of women who were induced at 38 weeks with those who were managed expectantly and did not deliver until at least 39 weeks. Separately, they looked at women induced at 39 weeks and compared them with those who were managed expectantly and did not deliver until at least 40 weeks.

“We found that at either 38 or 39 weeks, induction of labour decreased the rates of cesarean section quite dramatically—by about 27%, a finding which may have huge implications in terms of complications, costs and resources,” says Melamed.

Inducing labour at 38 weeks, however, was not risk-free. It came with a higher rate of neonatal morbidity and admission to the neonatal intensive care unit for jaundice and low blood sugar levels.

“Our study provides more support to induce labour at 39 weeks because it results in a similar decrease in cesarean section rate like 38 weeks, but at the same time it doesn’t have adverse effects on the baby,” he says.

Melamed notes the results provide a foundation to establish guidelines and protocols. Dr. Jon Barrett, director of the Women & Babies Research Program at SRI, agrees. “This will change practice and impact the timing of delivery of patients with gestational diabetes,” says Barrett. “A very basic question: ‘When is the best time to deliver?’ was extremely well answered by Dr. Melamed and his team. It gives clear direction to a common practice.”

The study will help inform future trials supported by the Greater Toronto Area-Obstetrical (GTA-OBS) Network, which Barrett established in 2013. Sunnybrook leads the 16-hospital-strong network, which accounts for more than 65,000 births annually.

— Eleni Kanavas

Melamed’s research is supported by the GTA-OBS Network. Barrett holds the Waks Family Chair in Maternal-Fetal Medicine Research.