Maternal diabetes may nearly quadruple the risk of infant death and double the risk of birth defects, a new study shows.

Doctors already knew diabetes can be a major health threat to fetuses and newborns. The new study, published in BMJ Online First, shows the magnitude of that threat.

Mary Macintosh, MD, and colleagues studied 2,359 pregnancies among diabetic women in England, Wales, and Northern Ireland. Macintosh is the medical director for the London-based Confidential Enquiry into Maternal and Child Health.

The deliveries occurred from March 2002 through February 2003. The group included women diagnosed with type 1 diabetes (1,707 women) or type 2 diabetes (652 women) at least a year before the estimated delivery date.

Data came from 231 maternity units in England, Wales, and Northern Ireland that treat women with diabetes.

Planning a Pregnancy When You Have Diabetes

Higher Rate of Infant Deaths, Birth Defects

Infant deaths and birth defects were more common among women with diabetes than in the general population, according to the study.

During the study, the diabetic women had 63 stillborn babies and 75 babies who died within a week of birth. Perinatal death (stillbirth or death within seven days after birth) equaled 32 per 1,000 births for women with type 1 or type 2 diabetes.

That rate is “nearly four times higher than that in the general maternity population,” write Macintosh and colleagues.

A total of 141 major birth defects were identified and confirmed in 109 babies. The rate of birth defects was 46 per 1,000 births -- that’s more than double the general public’s rate of 21 per 1,000 births.

The increased risk of birth defects was highest for congenital heart disease and abnormalities of the nervous system. Those problems were roughly three times more common in the diabetic women than in the general public.

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Study’s Limits

The study doesn’t prove diabetes was responsible for any infant deaths or birth defects.

Perinatal death and birth defects can happen for many reasons and aren’t limited to people with diabetes. Doctors often can’t pinpoint an exact reason for infant deaths or birth defects.

Other factors may have played a role in the study’s findings. For instance, the data shows a relatively high number of babies born with neural tube defects, a problem that has been linked to inadequate intake of the B vitamin folic acid (folate).

In the U.S., enriched grain products, such as flour, are fortified with folic acid. The U.K. doesn’t do this, but the British government is consulting consumers about a plan to do so.

In Macintosh’s study, women with type 2 diabetes were more likely than those with type 1 to be ethnic minorities and to come from economically disadvantaged neighborhoods. It’s hard to know what impact those factors might have had on the results.

Meanwhile, women with diabetes who are pregnant or plan to become pregnant should work with their doctors to boost their chances of having a safe pregnancy. Controlling diabetes is important for everyone with diabetes, pregnant or not.

Diabetes Care in the U.S. Improving

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Macintosh, M. BMJ Online First, June 16, 2006. BMJ.com: “News Roundup,” April 15, 2006. News release, BMJ.