Pregnant women who are obese or have diabetes are more likely to have abnormally large babies. A new study suggests that this rapid fetal growth happens early in pregnancy.
The research conducted by researchers at the University of Cambridge found that babies born to mothers who were obese or had gestational diabetes were abnormally large by the sixth month of pregnancy.
Gestational diabetes is a condition that affects women during pregnancy, with those who are obese at higher risk. Pregnant women who are routinely screened for diabetes, but often not until the sixth month (24 weeks).
"Our study shows that the babies of obese women were more likely to be excessively large around the abdomen even as early as 20 weeks [into pregnancy]," said Smith.
"Women who were diagnosed with pregnancy-related diabetes showed a similar pattern -- though their babies' rapid growth became apparent a bit later, at the 28th week of pregnancy," he said.
The U.S. Preventive Services Task Force recommends that women be screened for gestational diabetes after the 24th week of pregnancy.
"But, the American Congress of Obstetricians and Gynecologists (ACOG) does advise earlier screening for women at increased risk of pregnancy-related diabetes -- including those who are obese," said Dr. Raul Artal, professor emeritus of obstetrics and gynecology at Saint Louis University School of Medicine, in St. Louis.
If a pregnant woman screens negative for gestational diabetes, the test should be repeated between the 24th and 28th week of pregnancy, he added.
Researchers at the Department of Obstetrics & Gynecology at the University of Cambridge analyzed data from the Pregnancy Outcome Prediction study, which followed more than 4,000 first time mothers who were followed through pregnancy.
Ultrasound scans were used to assess the growth of their babies in the womb. The abdominal and head circumference of the fetuses were measured and compared the growth in women who developed gestational diabetes with those who did not.
About 4.2% were diagnosed with gestational diabetes during or after the 28th week of pregnancy. The researchers found no association between the size of the child at 20 weeks and the mother subsequently developing gestational diabetes. However, the fetus of the women diagnosed with gestational diabetes grew abnormally large prior to diagnosis, between 20 and 28 weeks. The findings suggest that the onset of fetal growth disorder in gestational diabetes predates the usual time of screening.
It is well known that maternal obesity is a risk factor for childhood obesity. Even in the absence of gestational diabetes, the babies born of obese women were also twice as likely to be big at 28 weeks. Both obesity and gestational diabetes were associated with an almost 5-fold risk of excessive fetal growth by the 28th week scan.
"Our study suggests that the babies of women subsequently diagnosed with gestational diabetes are already abnormally large by the time their mothers are tested for the disease," says Dr Ulla Sovio from the Department of Obstetrics and Gynecology at the University of Cambridge, the study's first author. "Given the risk of complications for both mother and child from gestational diabetes, our findings suggest that screening women earlier on in pregnancy may help improve the short and long-term outcomes for these women."
"Early screening may be particularly beneficial for obese women as fetal growth is already abnormal by 20 weeks among these women. Any intervention aimed at reducing the risk of abnormal birthweight in the infants of obese women may need to be implemented even earlier."
"We know that the offspring of women with gestational diabetes are at increased risk of childhood obesity, but so far no clinical trials have successfully demonstrated that screening and intervention in pregnancy reduce this risk. Our study suggests a possible explanation: screening and intervention are taking place when the effects of gestational diabetes are already manifested in the fetus," said Smith.
"The evidence from our study indicates that there is an urgent need for trials to assess the effect of earlier screening, both on the outcome of the pregnancy and the long term health of the offspring."
The report was published in the journal Diabetes Care.