Obesity and gestational diabetes linked to excessive fetal growth

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Babies of women who are both obese and develop gestational diabetes are five times as likely to be excessively large by 6 months of pregnancy, according to research published in Diabetes Care.
[gestational diabetes in pregnancy]
Gestational diabetes can put both mother and baby at risk.

Gestational diabetes is one of the most commonly acquired disorders of pregnancy, and obesity increases susceptibility.

Estimates vary as to its prevalence, but according to the Center for Vulnerable Populations at San Francisco General Hospital and Trauma Center, gestational diabetes affected somewhere between 7-18% of pregnancies in the US in 2013.

The condition can affect the mother’s health and cause excessive growth in the unborn child. The Centers for Disease Control and Prevention (CDC) explain that when the baby’s blood sugar is too high, the baby becomes “overfed,” leading to extra growth.

This increases the risk to the mother when giving birth, and the child is more likely to develop obesity and diabetes later in life.

Control of gestational diabetes is normally possible through diet and exercise; if not, medication is available.

At 8-12 weeks of pregnancy, women are screened for gestational diabetes through a blood glucose test, and, according to current guidelines in the US and the UK, those at greatest risk can have a full test at 24-28 weeks. In reality, most women attend screening at 28 weeks.

Five-fold increase in chance of fetal overgrowth

Researchers from the Department of Obstetrics & Gynecology at the University of Cambridge in the UK analyzed data for over 4,000 first-time mothers.

The mothers were part of the Pregnancy Outcome Prediction study, which used ultrasound scans to collect data on abdominal and head circumference, in order to assess fetal growth.

Researchers compared the growth of babies whose mothers had gestational diabetes with those whose mothers did not.

At or after 28 weeks, 4.2% of mothers received a diagnosis of gestational diabetes.

At 20 weeks, there was no link between the size of the child and a later emergence of gestational diabetes.

However, from 20-28 weeks, there was excessive growth among fetuses of women who were later found to have gestational diabetes. In other words, by the time diagnosis took place, at 28 weeks, the babies were already large.

The findings suggest that fetal growth disorder in gestational diabetes starts before screening usually takes place.

This means that current screening programs may be too late in the pregnancy to prevent long-term health effects on the child.

Maternal obesity is a common risk factor for childhood obesity, so the researchers also examined data for women who were obese. Even without a diagnosis of diabetes, the babies of women with obesity were twice as likely to be big at 28 weeks.

If a mother had both obesity and gestational diabetes, the risk of excessive fetal growth by 28 weeks was almost five times greater.

Need to review the timing of screening

First author Dr. Ulla Sovio points out that babies of women with gestational diabetes are already abnormally large by the time their mothers are tested. She suggests screening women earlier to improve outcomes in the short and long term.

Senior author Prof. Gordon Smith notes that clinical trials have not shown that screening and intervention in pregnancy reduce the risk of childhood obesity.

The current study, he says, suggests this is because screening and intervention come too late, when the fetus is already experiencing the effects of gestational diabetes.

Prof. Smith calls for trials to assess whether earlier screening would make a difference to the outcome of the pregnancy and the child’s long-term health.

Janet Scott, research and prevention lead for the stillbirth charity Sands, the stillbirth and neonatal death charity, says:

“We know from recent enquiries that failure to screen for gestational diabetes currently plays a part in a significant number of potentially avoidable stillbirths at term. Good risk assessment is crucial to avoiding harm to mothers and babies, and we welcome these important findings.”

Scott believes the findings could help improve antenatal care for high-risk pregnancies.

Medical News Today reported last year on research suggesting that depression and a sedentary pregnancy could be risk factors for gestational diabetes.

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