Competing interests: LC has spoken at a meeting of the Confidential Enquiry into Maternal and Child Health (CEMACH). AD has received funding from pharmaceutical companies (for consultancy, conference expenses, lecture fees, and research); she is a former officer of the Royal College of Physicians and a former member of the Working Lives intercollegiate committee. RG has received funding from pharmaceutical companies (for advisory services, consultancy, conference expenses, and lecture fees); he is medical adviser to Warwick Diabetes Care at the University of Warwick, chairman of trustees of Pregnancy Sickness Support, and honorary treasurer of the Primary Care Diabetes Society. JH is chair of the neonatal working group for the CEMACH Diabetes in Pregnancy Enquiry, and an adviser and speaker for Baby Friendly Initiative, BLISS, and CEMACH. RH has received funding from pharmaceutical companies (for consultancy, conference expenses, lecture fees, research, and educational support); he is chair of the Professional Advisory Council of Diabetes UK. JW has received funding from pharmaceutical companies (for advisory services, conference expenses, lecture fees, educational support, and working on a helpline); she is a member of Diabetes UK and has participated in CEMACH meetings and attended a meeting of the Management of Diabetes Excellence group.