Effect of management policy upon 120 Type 1 diabetic pregnancies: policy decisions in practice

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.

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.

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).

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.