Diabetes Care, Vol 21, Issue 4 535-538, Copyright © 1998 by American Diabetes Association
The effect of glycemic control in the pre-conception period and early pregnancy on birth weight in women with IDDM
AE Gold, R Reilly, J Little and JD Walker
Department of Diabetes, Royal Infirmary, Edinburgh, Scotland, U.K.
OBJECTIVE: To examine data from pregnancies in women with IDDM to assess
the relative effects of mean glycosylated hemoglobin levels before
conception, at booking, and during the 3 trimesters of pregnancy on birth
weight. Good glycemic control during pregnancy in women with IDDM is
important to minimize the risk of fetal malformation and macrosomia. Recent
studies have suggested that glycemic control in the 1st trimester is more
important than glycemic control during the 2nd or 3rd trimesters. RESEARCH
DESIGN AND METHODS: The case records of 65 deliveries to women with IDDM
were reviewed. Fifty-seven deliveries were included in the present study.
Of the deliveries reviewed, 32 women were in their first pregnancy and 25
women were multiparous. Only viable pregnancies were included because the
major outcome variable of interest was birth weight. Glycosylated
hemoglobin was recorded for each time period. RESULTS: The median
standardized birth weight was 1.1 SD higher than the nondiabetic mean. When
pregnancies, in which the birth weight was greater than 1 SD above the
nondiabetic mean, were compared with pregnancies, in which birth weight was
less than 1 SD above the mean, significant differences were observed
between the groups in HbA1 at 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 = 0.03), at booking (9.5 +/- 2.2 vs. 8.4 +/- 1.6%, P = 0.04),
and at 0-12 weeks' gestation (9.5 +/- 2.2 vs. 8.0 +/- 1.3%, P = 0.04), but
HbA1 later in pregnancy did not differ significantly between the groups.
Correlational analysis of all 57 pregnancies revealed significant
correlations between birth weight and HbA1 at 0-6 months pre-conception (r
= 0.44, P = 0.002), at booking (r = 0.43, P = 0.001), at 0-12 weeks'
gestation (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, with
stepwise regression analysis, only HbA1 at 0-12 weeks' gestation entered
into the equation with a multiple r value of 0.48. CONCLUSIONS: Glycemic
control in the immediate pre-conception period and early 1st trimester
appears to have a greater influence on birth weight than does glycemic
control during the later weeks of pregnancy.