Timing of Screening and Diagnosis for Gestational Diabetes: Effects on maternal and neonatal health outcomes

Abstract

Introduction: Gestational Diabetes Mellitus (GDM) is a condition with rising prevalence. GDM if left untreated leads to health complications for mothers and their babies such as pre-eclampsia, perineal trauma, caesarean section, Large for gestational age infant (LGA), macrosomia, birth injury (shoulder dystocia, bone fracture, nerve palsy) and long term metabolic problems. GDM is tested for and diagnosed so that treatment to reduce the incidence of adverse health outcomes can commence. The time at which testing occurs varies by location but does not appear to be based on clinical or scientific evidence. Aim: To investigate how timing of testing for GDM affects maternal and neonatal health outcomes. Methods: A systematic review synthesised information from studies which specified time (gestational age) at testing and reported maternal and neonatal outcomes in relation to this time. A comprehensive search resulted in 10 studies being eligible for inclusion in the review; 1 quasi-randomised trial and 9 cohort studies. Risk of bias was assessed, data extraction performed and data meta-analysed in Review Manager (Revman) with Forest Plots. Odds ratios with 95% confidence intervals described the effect of early or late screening for GDM on the chance of adverse health outcomes occurring, and the influence of early or late screening on the effect GDM had on adverse health outcomes. Results: Included studies had an overall low risk of bias, and data were available for 16 maternal and neonatal health outcomes. Statistically significant increases in the chances of a LGA infant, macrosomia and caesarean section were identified if women were tested for and diagnosed with GDM later in pregnancy compared with earlier. The effect of GDM on the chance of a woman having a caesarean section was also greater if GDM was tested for and diagnosed later in pregnancy (≥28 weeks’ gestation). Conclusion: Testing for and diagnosing GDM earlier rather than later in pregnancy allows for earlier intervention and appropriate management of hyperglycaemia, reducing the chances of large babies and associated complications. Randomised controlled trials should be conducted to identify the gestational age window where diagnosis and treatment is optimum for prevention of adverse outcomes.