Women with type 1 diabetes should keep their blood glucose levels well controlled before they become pregnant, in order to minimize the risk of serious adverse pregnancy outcomes, results of a large Danish study indicate.

A blood measurement known as A1C is an indicator of how well glucose levels are kept in the normal range over the long term. The goal of the present study was to find a threshold pre-conception value for A1C below which the risk of having a baby with malformations or that dies soon after birth is no higher than in the general population.

The study looked at 933 women with diabetes who were having their first baby. Forty-five babies were born with birth defects, including 23 that were major, and 31 infants died before or soon after delivery, of which 5 involved major malformations, Dr. Dorte Jensen, at the University of Southern Denmark, Odense, and her associates report in the medical journal Diabetes Care.

They found that the risk of serious adverse outcomes was statistically no higher than for the background population when women with diabetes had A1C readings of less than 6.9% around the time of conception.

The risk of serious adverse outcomes increased gradually with levels of A1C above 6.9% and doubled when it reached 10.3%; at A1C readings of 10.4% or greater, the risk quadrupled.

"In conclusion," the investigators write, "the results of this study support a recommendation of preconceptional A1C levels less than 7% in women with type 1 diabetes, emphasizing the importance of prepregnancy counseling."