Diabetes and pregnancy

The evidence that rates of type 2 diabetes in pregnancy are rising is largely based on global figures¹ and individual clinicians' reports of younger pregnant women with the condition.² Until recently, care for women with diabetes in pregnancy has focused on type 1 diabetes. A paper in this week's BMJ finds that high rates of congenital anomalies, stillbirth, and neonatal death were reported in women with type 2 diabetes as well as those with type 1 diabetes.³

Data on trends and variations in prevalence in pregnancy are sparse and based largely on indigenous and migrant populations in North America and New Zealand.² Comparisons between studies are difficult as inclusion criteria are inconsistent. Studies vary according to whether they count miscarriages or terminations in their adverse outcomes and whether they include women who are diagnosed as having diabetes in pregnancy and are subsequently found to have type 2 diabetes. Migration of women from countries in Africa and South Asia with high rates of type 2 diabetes has increased the observed prevalence in western European and North American countries; consequent lifestyle changes may have compounded this increased prevalence.

The Confidential Enquiry into Maternal and Child Health undertaken in England, Wales, and Northern Ireland audited 3808 pregnancies in 3733 women with pregestational diabetes who booked for care or delivered between 1 March 2002 and February 2003.⁴ The article by staff from the confidential inquiry in this week's BMJ is based on the 2359 pregnancies audited in the women whose diabetes was diagnosed at least a year before the pregnancy.³ Perinatal mortality rates in babies of women with type 1 and 2 diabetes were similar (31.7 and 32.3 per 1000 total births respectively) and nearly four times higher than in the corresponding general population; for both types of diabetes, the prevalence of major congenital anomalies was more than double that expected. The study supports the view that type 2 diabetes requires the same level of care as type 1 diabetes.³

However, the study made no statistical adjustment for the high proportion of South Asian women in the type 2 diabetes group, 16% of whom were of Pakistani origin, a group with high rates of congenital anomalies. Compared with the white population, this population of Pakistani origin is less likely to choose terminations for fetal anomaly. As most terminations occur before 24 weeks of gestation and are therefore cannot be registered as stillbirths in England and Wales, this white population appears to have a lower loss rate. As a result, the perinatal mortality rates are not comparable. A recent study in Bradford adjusted for ethnic origin and showed that diabetes increased the rate of congenital anomalies among Pakistani women. In addition, rates were higher in women with type 2 diabetes who were using insulin.⁵

Better care before conception and good glycaemic control can improve outcome in women with diabetes.⁶ Women with diabetes and their clinicians should recognise the possibility of pregnancy, particularly at the extremes of reproductive age. Contraception should be available to minimise unplanned pregnancies, since women need to optimise glycaemic control before planning a pregnancy. Women being treated for subfertility in particular need to have good glycaemic control before conception.

Because of the high rate of neural tube defects in women with diabetes, women should take 5 mg of folic acid a day when planning pregnancy. The high rate of cardiac anomalies requires detailed fetal cardiac assessment, which may be difficult to provide in many areas and countries. The benefit of interventions in late pregnancy to reduce stillbirth is less clear, since optimisation of glycaemic control to avoid macrosomia and early delivery has not yet reduced stillbirth rates. A study in the Netherlands of women with type 1 diabetes (84% of whose pregnancies were planned) showed that even though good control could be achieved, complication rates were still higher than for women without diabetes.⁷

This continuing high rate of problems therefore implies that close monitoring and interventions aimed at avoiding late intrauterine death should continue.

As in earlier studies in the United Kingdom and elsewhere, the management of many women in the study by Macintosh and colleagues fell short of recommended standards.³,⁴ This may be because women with type 2 diabetes were more likely to live in disadvantaged areas and come from black and minority ethnic groups.³ Some of these women may have been migrants with difficulties in accessing appropriate care—for example, because of language difficulties or unfamiliarity with the healthcare system. A further stage of the larger study, based on an examination of samples of case notes by confidential enquiry panels, should give a fuller picture of this and other aspects of care.⁴

In view of these difficulties, efforts to improve outcomes should focus on identifying at risk groups—in particular, women with a history of gestational diabetes—as well as on opportunistic screening for early case finding. Ideally, public health measures are needed to prevent the onset of type 2 diabetes, especially among younger women.¹,⁸ This will be challenging in countries where the prevalence of type 2 diabetes is much higher than in the United Kingdom, and where there is limited access to pre-pregnancy and pregnancy care.