Commentary: Controversies in management of diabetes from preconception to the postnatal period

Why does the United Kingdom remain so far from achieving the aim of “a pregnancy outcome for women with diabetes that equates with that of women without diabetes,” an aim outlined at the landmark St Vincent meeting of diabetes experts, government representatives, and patient organisations nearly 20 years ago?¹ Pregnancy outcomes in the UK continue to be substantially worse for women with pre-existing diabetes (both type 1 and type 2), with rates of congenital anomalies and perinatal mortality significantly higher than in non-diabetic women and with care regularly falling short of the required standard.² Many of the recommendations in the new guidelines from the National Institute for Health and Clinical Excellence (NICE) seem sensible and will be of use to all healthcare professionals in this area, but in places they are surprisingly clear cut given the relative paucity of high quality evidence.

The guidelines suggest a comprehensive programme of care from preconception to postnatal management. They include a strong emphasis on preparation for pregnancy, which requires considerable involvement of general practitioners, diabetologists, specialist obstetricians and midwives, and most importantly the women themselves. This message has been echoed by the latest triennial maternal mortality report from the UK, which highlights the importance of joined-up care for such women.³ Given that two thirds of pregnant women with pre-existing diabetes had a haemoglobin A_1C concentration greater than 7% in the first trimester (the threshold for optimal glycaemic control in the report from the Confidential Enquiry into Maternal and Child Health),² achieving the recommendation of aiming to “maintain a HbA_1C below 6.1%” seems particularly optimistic. Much greater uptake of structured education programmes and use of continuous subcutaneous insulin infusion pumps, as shown to be beneficial outside pregnancy, may need to be considered to achieve these tough targets. The resource implications should not be underestimated, particularly when those with poorest control may find it hardest to access and use health care.

The recommendation that screening for gestational diabetes should be by clinical risk factor alone is more controversial. The authors acknowledge the poor sensitivity and specificity of this approach compared with universal administration of oral glucose tolerance tests. In some groups, use of clinical risk factors misses nearly half the women with gestational diabetes,⁴ but the performance of this screening method will depend on the maternal age, ethnicity, and body mass index profile of each population. As the ACHOIS trial⁵ provided evidence of potential benefit for treatment of even mild gestational diabetes, missing a substantial proportion of cases of gestational diabetes may translate into clinical detriment. The ongoing hyperglycaemia and pregnancy outcome trial (which is assessing associations of maternal glycaemia with risks of adverse pregnancy outcome) will clarify further the need for treatment in this milder group. On a positive note, the option to use metformin for the treatment of gestational and type 2 diabetes will be welcomed as an alternative or addition to insulin.

Obstetricians may be surprised, given the limited evidence, at the recommendation to offer delivery to all women with diabetes at 38 weeks’ gestation as this will represent a change in clinical practice for many. It reflects the difficulty with which late pregnancy complications, particularly shoulder dystocia and stillbirth, can be predicted. Women with diabetes already have a caesarean section rate of 60-70%, three times higher than the rate in the general population of women giving birth; the debate continues about the most appropriate rate for caesarean section in diabetic women, given the short and long term risks of this procedure, particularly in obese women. Optimising glycaemic control to prevent macrosomia and understanding the mechanism by which diabetes increases the risk of stillbirth may be more thoughtful approaches in the long term.

In conclusion, many of the NICE recommendations will prove beneficial in ensuring that women with pre-existing or gestational diabetes receive comprehensive care that aims to minimise risks to mother and baby. The recommendations will be most helpful for clinicians managing predominantly white women with type 1 diabetes and a high uptake of medical care and low deprivation; however, in areas with an increasingly obese, ethnically diverse population and a high risk of type 2 and gestational diabetes, implementation will be more challenging.