High maternal blood sugar levels and Body Mass Index (BMI) were found to be the main risk factors associated with stillbirth in women with diabetes.
“Achievement of near normal blood sugar levels remains key to reducing risk”
Researchers from the University of Glasgow studied the health records of 5,392 singleton babies born to 3,847 mothers with pre-pregnancy diabetes in Scotland between April 1998 and June 2016.
The stillbirth rates among mothers with type 1 diabetes was 16.1 per 1,000 births, and 22.9 per 1,000 births in those with type 2 diabetes. This compared with 4.9 per 1,000 births in the general population.
The researchers found that one third of stillbirths in mothers with diabetes occurred close to full-term.
Mortality rates were highest for babies born small for their gestational age, but large infants were also at increased risk.
The study, carried out by Dr Robert Lindsay and Dr Sharon Mackin, of the Institute of Cardiovascular and Medical Sciences, University of Glasgow, was published today in the journal Diabetologia.
The authors noted that maternal obesity, older age mothers and smoking were already known to be key “modifiable” risk factors for stillbirth but data on pregnancies complicated by diabetes was more limited.
They said stillbirth rates among diabetic mothers had stayed high over recent years despite improvements seen in pregnant women in general.
In line with other studies, maternal blood glucose level was found to be the key risk factor for stillbirth.
Women with type 1 diabetes who suffered stillbirth had higher average blood glucose levels at all stages of pregnancy.
Whereas pre-pregnancy blood glucose levels appeared to be a more important predictor of stillbirth in women with type 2 diabetes.
Nevertheless, the authors found that in clinical practice mothers with type 2 diabetes were less likely to take up pre-pregnancy counselling around blood sugar control than those with type 1.
“Achievement of near normal blood sugar levels remains key to reducing risk,” the authors suggested.
They said health professionals needed methods of supporting women to improve blood glucose levels in pregnancy.
Another risk factor for stillbirth in mothers with type 2 diabetes was found to be high maternal BMI.
Maternal obesity is known to increase the chance of stillbirth in all women because it is associated with higher rates of preeclampsia, congenital abnormalities and fetal overgrowth.
Therefore, women also needed weight management support before and during their pregnancy, the authors said.
Meanwhile, the study authors said optimal timing of delivery in mothers with diabetes remained “controversial”.
“Midwives play a key role in advising and supporting women to eat more healthily”
They noted how many medical authorities including the National Institute for Health and Care Excellence in England recommended an early delivery for diabetic mothers.
Previous studies have shown that the risk of stillbirth increases five-fold at full-term and in this study a third of stillbirths happened in the final stage of pregnancy.
“It would seem then that earlier delivery would be a sensible approach,” said the authors.
“However, because of potential issues with early delivery – including respiratory distress syndrome as a result of inadequate lung development – we suggest that the increased risk of neonatal morbidity needs to be more formally explored before recommendations for optimal timing of delivery are made, particularly where mothers are managing to obtain almost normal blood glucose levels.”
The study also “unexpectedly” found that a high proportion of stillborn babies (81%) were male among the mothers with type 2 diabetes – four times higher than the rate in female babies.
However, the authors warned that the overall numbers were low and more studies on this matter would be “useful”.
They suggested that the higher stillbirth rate for boys could be explained by a combination of a higher metabolic demand, known to occur for male foetuses in the later stages of pregnancy, with a vulnerability caused by male foetuses having smaller placentas.
Responding to the research, Birte Harlev-Lam, executive director of professional leadership at the Royal College of Midwives, said the findings built on existing evidence that woman with existing diabetic conditions required additional monitoring during their pregnancies in line with national guidance.
However, she said there was currently no UK guidelines on what constituted a safe weight gain during pregnancy despite the increased risk of developing gestational diabetes if becoming overweight.
She said midwives were well placed to support women with their weight before and during pregnancy but they needed to be given the time and resources to do this.
“Midwives play a key role in advising and supporting women to eat more healthily so it is vital they have enough time to spend with women to promote and discuss the benefits of eating a healthy balanced diet,” she added. “We also need to ensure that women who require support services are signposted to appropriate weight management services and social support.”