Gestational Diabetes Prevalence High, CDC Says

Meg Barbor

June 25, 2014

The prevalence of gestational diabetes mellitus (GDM) in the United States may be as high as 9.2%, according to a new report from the Centers for Disease Control and Prevention (CDC).

"The true prevalence of [GDM] is unknown," write Carla DeSisto, MPH, from the CDC, and colleagues, but the closest estimates are based on data collected from birth certificates and the Pregnancy Risk Assessment Monitoring System (PRAMS) questionnaire. According to their study, 1% to 14% of pregnant women in the United States could develop GDM annually, depending on the type of diagnostic test used and the population studied. The study was published in the June 19 issue of Preventing Chronic Disease.

The purpose of the study was to determine GDM prevalence rates on the basis of birth certificates and PRAMS questionnaires and to compare GDM prevalence identified on the PRAMS questionnaires across 2007-2008 and 2009-2010. PRAMS is "an ongoing, state-based, population-based surveillance system that collects information about maternal behaviors before, during, and after pregnancies that result in live births," the authors write.

Women with GDM have a high risk of developing complications related to pregnancy and delivery, such as infant macrosomia, neonatal hypoglycemia, and cesarean delivery. In addition, they are more than 7 times as likely to develop type 2 diabetes 5 to 10 years later.

Their offspring also have an increased risk of developing impaired glucose tolerance and metabolic complications. Risk factors for GDM include family history of diabetes mellitus, overweight and obesity, nonwhite race, advanced maternal age, and higher parity.

Limitations in Prevalence Assessments

According to the researchers, GDM prevalence rates obtained solely from birth certificates are likely underestimated. As of 2010, only 33 states and the District of Columbia were using the 2003 revised birth certificate, which separates prepregnancy diabetes from GDM. "Moreover, studies indicate that whereas specificity for GDM is high on the birth certificate, sensitivity is as low as 48%," the authors write.

Conversely, prevalence rates obtained from PRAMS may be overestimated. According to a validation study across 5 states, "61.8% of 277 study participants who reported GDM on the questionnaire did not have a GDM diagnosis in their prenatal or hospital medical records," the authors note. In an effort to reduce misclassification, CDC periodically updates its PRAMS questionnaire in accordance with evidence-based revisions.

The researchers defined GDM as present if it were reported on either a birth certificate or a PRAMS questionnaire and if the woman surveyed did not report a history of prepregnancy diabetes.

"[W]omen were asked to select from a list any problems they had during their most recent pregnancy, including 'high blood sugar (diabetes) that started during this pregnancy,' " the authors note, and the women also were asked whether a healthcare professional had told them they had GDM. The questionnaire also collected demographic data.

"Our data suggests that the prevalence of GDM in 2010 was between 4.6% (as reported on the birth certificate only) and 9.2% (as reported on either the birth certificate or PRAMS questionnaire). Although there was high agreement (94.1%) between the 2 sources, more cases of GDM are identified through the PRAMS questionnaire than from the birth certificate," the researchers report.

"Therefore, given the current limitations of both the birth certificate and PRAMS, true GDM prevalence is likely between the estimates obtained from the 2 sources," they note.

They found no difference in prevalence between the 2007-2008 period (8.1%) and the 2009-2010 period (8.5%).

Even using the most conservative estimates, GDM still affects almost 1 in 20 pregnant women in the United States, the researchers emphasize. This means many women and their children have an increased risk for obstetric complications and for developing type 2 diabetes later.

The authors have disclosed no relevant financial relationships.

Prev Chronic Dis. 2014;11:130415. Full text

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