223 GLYCOHEMOGLOBIN (Hb AIc): CORRELATION WITH MATERIAL BLOOD GLUCOSE CONTROL IN PREGNANCY

Abstract

Hemoglobin AIc (Hb AIc), the glycosylated form (β-chain) of Hb A, normally comprises <6% of total hemoglobin, but has been found by us previously in third trimester diabetic pregnancy to be elevated (7-10%) and to correlate with infant birth weight. In contrast, non-pregnant uncontrolled diabetics have glycohemoglobin levels which may be 8-15% and may represent the integrated mean blood glucose level over the previous weeks and months. Since fetal size in infants of diabetic mothers has been related to maternal third trimester blood glucose control, we examined the relationship between third trimester maternal Hb AIc and maternal blood glucose control. Twelve diabetic women without evidence of vascular disease and with singleton births had Hb AIc levels determined in their third trimester using Amberlite cation exchange chromatography. Mean random blood glucose values (n=5-32) for each subject were determined for the twelve week period prior to Hb AIc measurement. Hb AIc correlated significantly with mean random blood glucose (r=0.84, p <0.01) as well as birth weight corrected for gestational age (r=0.78, p <0.01). In eight of these same women who required insulin, Hb AIc was determined serially 5-8 months postpartum. Seven of eight had higher Hb AIc levels postpartum (6.0±0.5 vs 8.4±0.6, M±SEM) at a time when glucose management was not accomplished. We speculate that lower levels of Hb AIc later in diabetic pregnancy are due to better blood glucose control during this period.