Health consequences for mother and baby of substantial pre-conception weight loss in women with obesity

© 2019 Sarah Anna Lucy PriceObesity in women of child-bearing age is common. There is little evidence that modest weight loss using lifestyle modification alters pregnancy outcomes. Bariatric surgery results in substantial weight loss, which reduces the risk of adverse outcomes for the mother but may increase risks for the baby. In order to reduce obesity-related adverse pregnancy outcomes for both mother and baby, alternative approaches to the management of obesity in women planning pregnancy are needed. OBJECTIVE: This study aims to explore the health consequences of substantial pre-conception weight loss, compared with modest pre-conception weight loss, in women with obesity. OUTCOMES: Primary outcome: To determine if non-surgical substantial pre-conception weight loss (10-15% body weight) in women with obesity (BMI 30-55kg/m2) causes a 10% reduction in fasting glucose at 26-28 weeks’ gestation compared with modest pre-conception weight loss (≤ 3% body weight). Secondary outcome: To determine if non-surgical substantial (10-15% body weight) compared with modest pre-conception weight loss (≤ 3% body weight) in women with obesity (BMI 30-55kg/m2) results in a reduction in the rate of (1) a composite of gestational diabetes, gestational hypertension/pre-eclampsia, delivery 37 weeks’ gestation, (7) primary Caesarean section, (8) neonatal hypoglycaemia, (9) neonatal SCN/ICU admission, (10) maternal and neonatal length-of-stay, (11) a decrease in time-to-conception, (12) an increase in live birth rate (13) no difference in gestational weight gain. METHODS: This is a two-arm, parallel group, randomised controlled trial. 164 women with obesity (BMI 30–55 kg/m2), aged 18-28 years old and planning pregnancy were recruited via a social media platform. They were randomised to a 12-week intervention: modest weight loss (MWL ≤ 3% body weight) using a hypocaloric diet or substantial weight loss (SWL 10–15% body weight) using a modified very low energy diet (VLED). Completers of the intervention (Phase 1) were observed for 48-weeks (Phase 2: weight maintenance and Phase 3a: pre-pregnancy). Pregnancies were observed and pregnancy outcome data collected (Phase 3b). RESULTS: This thesis presents an interim analysis of results. In Phase 1, weight loss in MWL and SWL at Week 12 was 3.1% (3.2 0.6 kg) and 11.9% (13.0 0.5 kg) respectively (p<0.01). Cox proportional model demonstrated SWL had a significantly shorter time-to-conception than MWL (p=0.03). There was no difference in the change in fasting maternal glucose between baseline (pre-pregnancy) and 26-28 weeks’ gestation in those achieving modest (MWL -0.41 ± 0.14 (-7.6%)) and substantial (SWL -0.57 ± 0.11 (-10.6%)) pre-conception weight loss (p=0.40). A composite of pre-specified obesity-related adverse pregnancy outcomes was significantly reduced in SWL (34/21 events) compared with MWL (18/28 events) (p=