Pregnancy loss and neonatal death in women with type 1 or type 2 diabetes mellitus

Background: Diabetes mellitus (DM) is known to be a significant risk factor for pregnancy loss, either through still-birth or late intrauterine death or as the result of severe congenital malformation. Improved glycemic control and other advances in care substantially reduced the incidence of pregnancy loss in women with type 1 DM in most countries by the 1970s. However, because of a greater prevalence of obesity since the 1980s, the emergence of type 2 DM in pregnancy has become a significant problem. Although more pregnancies now occur in women with type 2 DM than in those with type 1 DM in many locations, relatively little information has been published about pregnancy loss in type 2 DM.

Objectives: This article examines the prevalence and causes of pregnancy loss in type 1 and type 2 DM and identifies factors in addition to glycemic control that may influence pregnancy outcome.

Methods: A MEDLINE search was conducted for recent literature on pregnancy loss in DM. Series reporting >200 pregnancies in type 1 DM and/or >100 pregnancies in type 2 DM were included.

Results: Thirty-four studies were identified (15 in type 1 DM [1997-2007], 19 in type 2 DM [1986-2007]). In type 1 DM, major congenital anomalies now account for ~50% of pregnancy losses, and all-cause perinatal mortality remains higher than in the general population. Several studies have suggested that the perinatal mortality rate is higher in type 2 DM than in type 1 DM. Factors other than glycemic control probably explain this phenomenon: women with type 2 DM typically are older and more obese, and they come from disadvantaged communities—all risk factors for pregnancy loss, particularly late intrauterine death and chorioamnionitis. In some women, type 2 DM may be recognized for the first time during pregnancy; pregnancies in these women carry the same risks of pregnancy loss as those in women with established DM.

Conclusions: Demographic changes in the prevalence of obesity suggest that the prevalence of type 2 DM in pregnancy will almost certainly increase. Although meticulous glycemic control is undoubtedly important in achieving good pregnancy outcomes, clinicians should be aware of the multiple risk factors faced by women with DM.