Change in Large for Gestational Age Birth Rates Over Time Related to Diabetes during Pregnancy Status: The Colorado Birth Registry 1989-2003

Background: Diabetes is increasing in the U.S. and diabetes during pregnancy is an important risk factor for birth related complications, including babies born large for gestational age (LGA).

Methods and Design: Retrospective analysis of data from the state of Colorado Birth Certificate Registry during 1989-2003 (n=886,019) was used to investigate trends in incidence of pregnancies complicated by diabetes and trends in LGA babies. The crude number of pregnancies and those complicated by diabetes were determined as well as change in birth weight by diabetes status adjusting for year of birth, gestational age, and maternal weight gain. Logistic regression was used to determine whether the effect of diabetes in pregnancy has changed over time with LGA as the outcome.

Results: The percentage of pregnancies complicated by diabetes, primarily gestational, has increased from 1.84% to 3.21% during this time. The average birth weight decreased over time, and was higher in diabetic pregnancies than controls. There was a significant trend (p<0.0001) towards decreased birth weight (9.2 grams/year) in the gestational diabetes pregnancies(GDPs) from 1995-2003 and a similar non-significant trend in pre-existing diabetic pregnancies. LGA decreased significantly after 1995 while LGA in controls has remained constant.

Conclusions: Pregnancies complicated by diabetes have increased in Colorado, but LGA among GDPs has decreased. This may indicate improvement in pre-natal care among pregnancies to mothers with pre-existing diabetes or mothers who develop diabetes during pregnancy. An alternative explanation is that Ob/Gyn physicians are recognizing the risk of LGA births and are delivering infants of diabetic mothers earlier.