Glycohemoglobin in diabetic pregnancy: a sequential study.

Glycohemoglobin (Hb Alc) was assayed sequentially during pregnancy and post partum in 53 women. In a group of nondiabetic women (N = 13) Hb Alc fell significantly (p less than 0.001) from the first to the third trimester and then rose to first-trimester levels by 12 weeks' post partum. Glycohemoglobin levels of insulin-dependent diabetic patients (N = 28) followed a similar pattern but at significantly elevated levels compared to nondiabetic patients (p less than 0.001). In contrast, patients with chemical diabetes (N = 12) did not manifest any change of Hb Alc with time, although they did have glycohemoglobin levels above those of the normal subjects during the third trimester (p less than 0.001) and before 12 weeks' post partum (p less than 0.02). It is speculated that these fluctuations in Hb Alc are most likely due to changes in long-term blood glucose control. Additionally, because Hb Alc increased in vitro oxygen affinity, some of these women were followed for parameters of oxygen transport as well. No significant changes of parameters of oxygen transport were found, with the exceptions of P50 in vivo and P50pH7.40 during the third trimester and of P50 in vivo before 12 weeks' post partum