THE EFFECT OF GLYCEMIC CONTROL IN THE PRE-CONCEPTION PERIOD AND EARLY-PREGNANCY ON BIRTH-WEIGHT IN WOMEN WITH IDDM

OBJECTIVE - To examine data from pregnancies in women with IDDM to ass ess the relative effects of mean glycosylated hemoglobin levels before conception, at booking, and during the 3 trimesters of pregnancy on b irth weight. Good glycemic control during pregnancy in women with IDDM is important to minimize the risk of fetal malformation and macrosomi a. Recent studies have suggested that glycemic control in the Ist trim ester is more important than glycemic control during the 2nd or 3rd tr imesters. RESEARCH DESIGN AND METHODS - The case records of 65 deliver ies to women with IDDM were reviewed. Fifty-seven deliveries were incl uded in the present study. Of the deliveries reviewed, 32 women were i n their first pregnancy and 25 women were multiparous. Only viable pre gnancies were included because the major outcome variable of interest was birth weight. Glycosylated hemoglobin was recorded for each time p eriod. RESULTS - The median standardized birth weight was 1.1 SD highe r than the nondiabetic mean. When pregnancies, in which the birth weig ht was greater than 1 SD above the nondiabetic mean, were compared wit h pregnancies, in which birth weight was less than 1 SD above the mean , significant differences were observed between the groups in HbA(1) a t 6-12 months pre-conception (10.0 +/- 2.3 vs. 8.6 +/- 1.4%, P = 0.02) , at 0-6 months pre-conception (10.2 +/- 2.4 vs. 8.7 +/- 2.0%, P = 0.0 3), at booking (9.5 +/- 2.2 vs. 8.4 +/- 1.6%, P = 0.04), and at 0-12 w eeks' gestation (9.5 +/- 2.2 vs. 8.0 +/- 1.3%, P = 0.04), but HbA(1) l ater in pregnancy did not differ significantly between the groups. Cor relational analysis of all 57 pregnancies revealed significant correla tions between birth weight and HbA(1) at 0-6 months pre-conception (r = 0.44, P = 0.002), at booking (r = 0.43, P = 0.001), at 0-12 weeks' g estation (r = 0.48, P = 0.001), at 12-24 weeks' gestation (r = 0.45, P = 0.001), and at 24 weeks to term (r = 0.34, P = 0.009). However, wit h stepwise regression analysis, only HbA(1) at 0-12 weeks' gestation e ntered into the equation with a multiple r value of 0.48.CONCLUSIONS - Glycemic control in the immediate pre-conception period and early Ist trimester appears to have a greater influence on birth weight than do es glycemic control during the later weeks of pregnancy.