By Lisa Rapaport

(Reuters Health) – Pregnant women with diabetes may be more likely to experience a stillbirth when they have obesity or poorly controlled blood sugar, a new study suggests.

Even without these extra health issues, women with diabetes who become pregnant face a four to five times higher risk of stillbirth than women without diabetes, and this risk has remained stubbornly high even as stillbirth rates have declined in the general population, researchers note in Diabetologia.

For the current study, researchers examined data on diabetic mothers who gave birth in Scotland between 1998 and 2016.

About 70% of the deliveries were in women with type 1 diabetes, the less common form of the disease, which develops in childhood or young adulthood when the pancreas can’t produce insulin. In Type 2 diabetes, which is linked with obesity and aging, the body can’t properly use or make enough insulin to convert blood sugar into energy.

Overall, the stillbirth rates were 16.1 for every 1,000 deliveries with type 1 diabetes and 22.9 for every 1,000 deliveries with type 2 diabetes.

With type 1 diabetes, higher blood sugar before conception or during late pregnancy was associated with stillbirth rates that were 3% to 6% higher.

For type 2 diabetes, elevated blood sugar before conception was tied to a 2% greater stillbirth risk, while higher BMI increased the risk by 7%

While most of the stillbirths happened when the fetus was premature, roughly one-third occurred when the pregnancy was full term.

“The question has to be asked whether earlier delivery of diabetic pregnancies could prevent these term stillbirths, but we don’t know the answer to this,” said Dr. Sharon Mackin, lead author of the study and a researcher at the University of Glasgow in Scotland.

“The optimal timing of delivery in pregnancy complicated by diabetes is not clear,” Mackin said by email.

The absolute risk of stillbirth was highest for infants who were small for their gestational age, particularly for mothers with type 1 diabetes.

Stillbirths were also more likely among infants who were large for their gestational age for mothers with both types of diabetes.

The study wasn’t a controlled experiment designed to prove whether or how specific factors might directly cause stillbirths among women with diabetes.

One limitation is that diabetes treatments changed dramatically over the study period and might have impacted stillbirth rates. Researchers also lacked data on some individual patient characteristics that might impact birth outcomes, and they had no details from death certificates to confirm what might have caused each stillbirth.

Doctors currently advise women with diabetes to deliver in the 38th week of pregnancy, Mackin said. Any sooner, and babies might have an increased risk of breathing problems from immature lung development.

“The risk of such breathing problems is higher in the 37th week than at later weeks,” Mackin said. “I think this is a key area of research that needs to be explored further before any further recommendations can be made to changing routine delivery care for these women.”

SOURCE: Diabetologia, online July 29, 2019.