Gestational impaired glucose tolerance does not increase perinatal mortality in a developing country: cohort study

Participants, methods, and results

The study hospital (catchment population 250 000; 4500 deliveries a year) accounts for 22% of deliveries of babies in Mauritius, hospital deliveries being 80% of all deliveries on the island.1 Cases were registered in 1993–6 at a joint obstetric and medical service for diabetes, and were also found by monitoring admissions to the obstetric wards, and by monitoring all requests for obstetric oral glucose tolerance tests. Data were collected from the mother and from hospital and national records. Diabetes and impaired glucose tolerance were diagnosed using the 1985 WHO criteria.2 Outcomes were assessed as miscarriage (<28 weeks), stillbirth, live birth, or neonatal death (<1 week). Neonatal data were obtained from neonatal records, and background information was obtained from national statistics and routinely collected hospital obstetric data. Standard statistical tests were used for analysis of categorical and continuous data.

A total of 294 glucose intolerant pregnancies were registered in 270 women with diabetes or impaired glucose tolerance (mean age 31; SD 6 years). Of these, 110 cases were of pregestational onset and the remainder were diagnosed during pregnancy (86 diabetes, 98 impaired glucose tolerance); nine were lost to follow up and 18 miscarried.

Outcome in the 267 pregnancies resulting in live birth or stillbirth is shown in the table. Perinatal mortality was 124/1000 for women with pregestational diabetes and 116/1000 for women with gestational diabetes, giving relative risks well above the rate in the background population (26/1000). There was no excess perinatal mortality in women with gestational impaired glucose tolerance (22/1000). The excess perinatal mortality in women with pregestational diabetes comprised a similar excess of stillbirths and early neonatal mortality; in gestational diabetes it was related particularly to an excess of stillbirths (81/1000). All but one of the cases of perinatal mortality in gestational diabetes occurred in 43 women who had fasting hyperglycaemia ≥7.8 mmol/l at presentation.

Mean birth weight was significantly higher in babies born to women with gestational diabetes and impaired glucose tolerance than in the background population but not in babies born to women with pregestational diabetes (table). The incidence of macrosomia was highest in the gestational diabetes group and was also significantly increased in the pregestational diabetes group. It was not significantly increased in the group with gestational impaired glucose tolerance, despite this group having the highest gestational age at delivery. Four infants of mothers with pregestational or gestational diabetes weighed ≥4500 g (2%; relative risk 9.2 (3.0 to 29.0)) but none weighed ≥4500 g in the group with gestational impaired glucose tolerance. Rates of caesarean section were significantly above background in all the glucose intolerant groups (table). Both hypoglycaemia and hyperbilirubinaemia were significantly more common in infants of women with pregestational and gestational diabetes than in those of women with gestational impaired glucose tolerance (table).

Comment

In Mauritius women diagnosed as frankly diabetic during pregnancy carry the same risks as women with pregestational diabetes, but pregnancies with gestational impaired glucose tolerance have an outcome identical to that of the background population across several measures. This is consistent with reports from Belfast and Bangkok. 3 4 The 1999 WHO Consultation reiterated that the term “gestational diabetes” should encompass both gestational impaired glucose tolerance and diabetes, and that women with impaired glucose tolerance should be managed as women with frank diabetes.5 Worldwide, most cases found on screening in pregnancy are of impaired glucose tolerance rather than diabetes. 3 4 Our data do not support using limited resources in developing countries to identify women with impaired glucose tolerance and to manage them in line with WHO recommendations.