Aims: To evaluate the outcome of two specific changes in the policy of managing pregnancy in Type 1 diabetes over a 5-year period. The need for change had been identified following an audit in the previous 5-year period: firstly, the need for intensive effort to improve the uptake of pre-pregnancy counselling; secondly, a modest relaxation of the targets for blood glucose control during labour to minimize the risk of maternal hypoglycaemia.
Methods: Data were collated from maternal and neonatal case notes from all women with Type 1 diabetes mellitus managed by Newcastle obstetric services between August 1989 and July 1994 (n = 80), comparing data with 40 such women looked after between November 1985 and July 1989.
Results: The age of the women, blood glucose control during pregnancy, gestation at delivery, and birth weight were similar in the 5-year period under study to those previously reported for the first study period. Mean blood glucose in labour for Period 2 was 5.5 +/- 0.6 mmol/l, exactly 1.0 mmol/l higher than the mean blood glucose achieved in labour for Period 1. As a consequence, only 22.5% women (18/80) experienced one or more episodes of blood glucose less than 3.0 mmol/l compared with 40.0% women in Period 1 (16/40) (P < 0.01). There was no effect of maternal blood glucose on neonatal blood glucose provided the former was within the range 4-8 mmol/l during labour. However, if maternal blood glucose was over 10 mmol/l, the infant's blood glucose was always low (1.3 +/- 0.8 vs. 2.5 +/- 1.5 P < 0.02). Macrosomia (over the 90th percentile for gestational age) was observed in 43.1% of infants in Period 1, and the mean birth weight was not different from Period 1. In the initial 5-year period 27.5% (11/40) women received specific pre-pregnancy care for their diabetes, compared with 21.3% (17/80) in Period 2 despite the intensive programme of education. There were six cases of congenital abnormality and two antepartum deaths (10% adverse outcome).
Conclusions: The target range for blood glucose control in labour of 4-7 mmol/l minimizes maternal hypoglycaemia in labour and the data indicate that an upper limit of 8 mmol/l would not increase the risk of neonatal hypoglycaemia. Fresh thought is required about the matter of preventing congenital abnormalities by achieving better pre-pregnancy and peri-conception blood glucose control.