Analysis of 44,279 blood glucose estimations in relation to outcomes in 80 pregnant diabetic women.

A retrospective study was conducted to assess glycaemic control in relation to pregnancy outcomes in pre-existing and gestational diabetics. Computerised blood glucose records from 47 pre-existing diabetic patients and 33 gestational diabetics were collected prospectively and then analysed retrospectively in relation to pregnancy outcomes. There were two spontaneous miscarriages from the pre-existing diabetic cohort. A total of 44,279 individual blood glucose estimations were made. The mean fasting glucose for pre-existing diabetic patients fell significantly throughout pregnancy, being 7.7+/-2.1, 7.2+/-3.1 and 6.5+/-2.4 mmol/l, respectively, for trimesters 1,2 and 3 (P<0.01). The mean post-prandial glucose for each trimester were 8.9+/-2.0, 8.6+/-1.6 and 8.2+/-1.2 mmol/l (P<0.01). The HbAlc for pre-existing diabetic patients for each trimester was 7.5+/-1.4%, 6.1+/-1.0% and 5.9+/-0.7%, respectively. Gestational diabetic patients had a mean fasting glucose of 5.6+/-1.5 mmol/l and a mean post-prandial glucose of 8.0+/-2.1 mmol/l during trimester 3. Home glucose monitoring correlated reasonably well with first trimester HbA1c (r2=0.43, P<0.001), but this relationship became less valid as pregnancy progressed. The mean gestation at delivery was 37 weeks, although 30% of women were delivered between 34 and 37 weeks and 8% delivered before 34 weeks. Labour was induced in 49% of patients and the overall caesarean section rate was 58%. The mean birth weight for pre-existing diabetic patients was 3479 g (1410-5000 g) and for women with gestational diabetes was 3605 g (1890-5920 g). For pre-existing diabetic patients HbA1c did not correlate with birth weight; however, home blood glucose data from trimester 2 did correlate (r2=0.15, P <0.005) and there appeared to be stronger relationship with trimester 3 data (r2=0.24, P <0.005). There was no association between trimester 3 glucose data and birth weight in the gestational cohort. The babies born to pre-existing diabetic mothers had a high incidence of admission to a neonatal unit and over 50% of the babies had proven hypoglycaemia. Our present computerised system for home blood glucose monitoring has shown that for pre-existing diabetes patients but not gestational diabetic patients, glycaemic control in the second and third trimester influences birth weight. The current degree of glycaemic control in the mothers did not prevent a high rate of neonatal hypoglycaemia.