The goal of the prospective, population-based study, conducted by Dr. Dorte M. Jensen and associates and reported in the June issue of Diabetes Care, was to find a threshold value for peri-conceptional A1C below which the risk of congenital malformation and perinatal mortality is higher than that of the general population.
The study cohort, drawn from the Danish Diabetes Association registry, included 933 primiparous, singleton pregnancies that were delivered after 24 weeks’ gestation (plus 3 that were terminated prior to 24 weeks because of congenital malformation).
There were 45 infants with congenital malformations, including 23 that were major, and 31 perinatal deaths, of which 5 involved major malformations, Dr. Jensen, at the University of Southern Denmark, Odense, and her associates report.
Compared with the background population, the relative risk of serious adverse outcomes was 1.6 for women whose periconceptional A1C was < 6.9% (p = NS). However, incidence of perinatal mortality -- 2.1% -- was significantly increased (RR = 2.8, p < 0.05), which probably reflects that “factors other than hyperglycemia, such as smoking, nephropathy, preeclampsia, preterm delivery, and A1c in late pregnancy, (also) affect perinatal mortality.”
The risk of serious adverse outcomes increased gradually with increasing levels of A1C between 6.9% and 10.3% (overall RR = 2.2, p < 0.05), until values reached 10.4% or greater, when the relative risk increased abruptly to 4.7.
“In conclusion,” the authors write, “the results of this study support a recommendation of preconceptional A1C levels < 7% in women with type 1 diabetes, emphasizing the importance of prepregnancy counseling.”
Diabetes Care 2009;32:1046-1048.