Dietary and lifestyle advice for women to prevent and treat pregnancy hyperglycaemia: identifying and closing research gaps

Abstract

Background Increased glycaemia during pregnancy is associated with adverse health outcomes for women and their babies. This thesis aimed to investigate and evaluate the strategies used for preventing, diagnosing and managing pregnancy hyperglycaemia. Methods Research methodologies used included Cochrane systematic review, qualitative semi-structured interview and a follow-up cohort study of women and babies within a randomised trial. Results Three Cochrane systematic reviews were conducted in identified research gaps. The first review assessed the effects of physical exercise for preventing gestational diabetes mellitus (GDM). Evidence from five randomised controlled trials involving 922 women and their babies suggested no differences in the incidence of GDM, caesarean section or operative vaginal birth between women who received additional exercise interventions and those having routine antenatal care. The second review assessed nine randomised trials involving 429 women and 436 babies investigated eleven different types of dietary advice within six different comparisons. No one type of dietary advice was more effective than others in reducing the risk of caesarean section, operative vaginal birth, large-for-gestational age or macrosomic infants. The third review assessed the effects of different types of management strategies for pregnant women with borderline GDM. Evidence from four randomised controlled trials involving 521 women and their babies suggested additional interventions, including dietary counselling and metabolic monitoring, helped reduce the number of macrosomic and large-for-gestational-age babies without increasing the risks of caesarean section or operative vaginal birth. All three systematic reviews highlighted the need for further, larger, well-designed trials. The qualitative semi-structured interview study explored women’s views on their diagnosis and management for borderline GDM. Twenty-two women attended the interviews. The diagnosis of borderline GDM caused concern for one third of women. The majority of women believed managing their borderline GDM was important and they planned to improve their lifestyle. Factors affecting women’s ability to achieve intended lifestyle changes varied greatly. The most important enabler was thinking about baby’s health. The most significant barrier was a lack of family support. The follow-up cohort study within a randomised trial followed 245 mother-baby pairs at four to 12 months after birth to assess their health. Additional lifestyle interventions during pregnancy for women with borderline GDM had no impact on primary outcomes of maternal weight retention at four months postpartum or their babies’ weight at four to 12 months of age, or any secondary outcomes, except infant subcutaneous adiposity at four months of age. Conclusion Synthesis of available evidence on different strategies for preventing and managing pregnancy hyperglycaemia does not yet permit clear guidance for clinical practice but indicates the need for further trials with long-term follow up to assess impact on mothers and their children. A diagnosis of borderline GDM appears to be a powerful motivator for women to change diet and exercise patterns. As new health knowledge becomes available from further completed trials, a timely update of the relevant Cochrane reviews to include these trials is warranted.