Joanna Tieu, Philippa Middleton, Caroline A Crowther, Emily Shepherd

Infants born to mothers with pre-existing type 1 or type 2 diabetes mellitus are at greater risk of congenital anomalies, perinatal mortality and significant morbidity in the short and long term. Pregnant women with pre-existing diabetes are at greater risk of perinatal morbidity and diabetic complications. The relationship between glycaemic control and health outcomes for both mothers and infants indicates the potential for preconception care for these women to be of benefit. This is an update of the original review, which was first published in 2010. To assess the effects of preconception care in women with diabetes on health outcomes for mothers and their infants. We searched Cochrane Pregnancy and Childbirth's Trials Register (31 January 2017) and reference lists of retrieved articles. Randomised controlled trials (RCTs) assessing the effects of preconception care for diabetic women. Cluster-RCTs and quasi-RCTs were eligible for inclusion but none were identified. Two reviewers independently assessed study eligibility, extracted data and assessed the risk of bias of the included studies. We checked data for accuracy and assessed the quality of the evidence using the GRADE approach. We included three trials involving 254 adolescent girls with type 1 or type 2 diabetes, with an overall unclear to high risk of bias. The three trials were conducted at diabetes clinics in the USA, and assessed the READY-Girls (Reproductive-health Education and Awareness of Diabetes in Youth for Girls) programme versus standard care.Considering primary outcomes, one trial reported no pregnancies in the trial period (12 months) (very low-quality evidence, with downgrading based on study limitations (risk of bias) and imprecision); in the other two trials, pregnancy was an exclusion criterion, or was not clearly reported on. None of the trials reported on the other primary maternal outcomes, hypertensive disorders of pregnancy and caesarean section; or primary infant outcomes, large-for-gestational age, perinatal mortality, death or morbidity composite, or congenital malformations. Similarly, none of the trials reported on the secondary outcomes, for which we had planned to assess the quality of the evidence using the GRADE approach (maternal: induction of labour; perineal trauma; gestational weight gain; long-term cardiovascular health; infant: adiposity; type 1 or 2 diabetes; neurosensory disability).The majority of secondary maternal and infant outcomes, and outcomes relating to the use and costs of health services were not reported by the three included trials. Regarding behaviour changes associated with the intervention, in one trial, participants in the preconception care group had a slightly higher score for the actual initiation of discussion regarding preconception care with healthcare providers at follow-up (nine months), compared with those in the standard care group (mean difference 0.40, 95% confidence interval -0.02 to 0.82 (on a scale of 0 to 4 points); participants = 87) (a summation of four dichotomous items; possible range 0 to 4, with 0 being no discussion). There are insufficient RCT data available to assess the effects of preconception care for diabetic women on health outcomes for mothers and their infants.More high-quality evidence is needed to determine the effects of different protocols of preconception care for diabetic women. Future trials should be powered to evaluate effects on short- and long-term maternal and infant outcomes, and outcomes relating to the use and costs of health services. We have identified three ongoing studies that we will consider in the next review update.