Effect of metformin in addition to an antenatal diet and lifestyle intervention on fetal growth and adiposity: the GRoW randomised trial

BACKGROUND

The infants born to women who are overweight or obese in pregnancy are at an increased risk of being born macrosomic or large for gestational age. Antenatal dietary and lifestyle interventions have been shown to be ineffective at reducing this risk. Our aim was to examine the effects of metformin in addition to a diet and lifestyle intervention on fetal growth and adiposity among women with a BMI above the healthy range.

METHODS

Women who had a body mass index ≥25 kg/m² in early pregnancy, and a singleton gestation, were enrolled in the GRoW trial from three public maternity hospitals in metropolitan Adelaide. Women were invited to have a research ultrasounds at 28 and 36 weeks' gestation at which ultrasound measures of fetal biometry and adiposity were obtained. Fetal biometry z-scores and trajectories were calculated. Measurements and calculations were compared between treatment groups. This secondary analysis was pre-specified.

RESULTS

Ultrasound data from 511 women were included in this analysis. The difference in femur length at 36 weeks' gestation was (0.07 cm, 95% CI 0.01-0.14 cm, p = 0.019) and this was was statistically significant, however the magnitude of effect was small. Differences between treatment groups for all other fetal biometry measures, z-scores, estimated fetal weight, and adiposity measures at 28 and 36 weeks' gestation were similar.

CONCLUSIONS

The addition of metformin to dietary and lifestyle advice in pregnancy for overweight and obese women has no clinically relevant effect on ultrasound measures of fetal biometry or adiposity.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry ( ACTRN12612001277831 ).

Rationale and study design for lifestyle intervention in preparation for pregnancy (LIPP): A randomized controlled trial

INTRODUCTION

Maternal obesity increases neonatal risk for obesity and metabolic syndrome later in life. Prior attempts to break this intergenerational obesity cycle by limiting excessive gestational weight gain have failed to reduce neonatal adiposity. Alternatively, pre-conception lifestyle interventions may improve the in utero metabolic milieu during early pregnancy leading to improved fetal outcomes. This randomized controlled trial (RCT) is evaluating whether a lifestyle intervention to reduce weight and improve maternal metabolism in preparation for pregnancy (LIPP) attenuates neonatal adiposity, compared to standard medical advice.

MATERIAL AND METHODS

Overweight/class 1 obese women after a previous pregnancy, ~12 weeks postpartum, preparing for a subsequent pregnancy, will be block randomized (1:1) to either LIPP or standard of care in a parallel design. Randomization is stratified by lactation status and overweight vs. class 1 obesity. The LIPP program consists of intensive short-term weight loss followed by weight maintenance until conception using supervised exercise and a low glycemic Mediterranean diet.

PRIMARY OUTCOMES

Group differences in neonatal adiposity at birth assessed by PEA POD and placental mitochondrial lipid metabolism.

SECONDARY OUTCOMES

Group differences in maternal pregravid and gestational body composition, insulin sensitivity, β-cell function, fasting metabolic and inflammatory biomarkers, and overall quality of life. Exploratory outcomes include umbilical cord blood insulin resistance, lipid profile and inflammation.

DISCUSSION

This RCT will determine the efficacy of maternal weight loss prior to pregnancy on reducing neonatal adiposity. Findings may change standard obstetrical care by providing Level 1 evidence on lifestyle interventions improving neonatal outcomes for women planning for pregnancy.

CLINICAL TRIAL REGISTRATION

NCT03146156.

The mediating effects of gestational diabetes on fetal growth and adiposity in women who are overweight and obese: secondary analysis of the LIMIT randomised trial

OBJECTIVE

To describe the mediating effect of maternal gestational diabetes on fetal biometry and adiposity measures among overweight or obese pregnant women.

DESIGN

Secondary analysis of the LIMIT randomised trial.

SETTING

Public hospitals, metropolitan Adelaide, South Australia.

POPULATION

Pregnant women with body mass index (BMI) ≥25 kg/m² and singleton gestation.

METHODS

Fetal ultrasound measures at 36 weeks of gestation and baseline BMI from women randomised to the LIMIT trial Standard Care group (n = 912 women) were used to conduct causal mediation analyses using regression-based methods.

MAIN OUTCOMES MEASURES

Ultrasound measures of fetal biometry and adiposity at 36 weeks of gestation.

RESULTS

Increased maternal BMI was associated with increased measures of fetal head circumference [direct (unmediated) effect 0.18 (95% CI: 0.05-0.31), P = 0.005; total effect 0.17 (95% CI: 0.02-0.31), P = 0.018], abdominal circumference [direct effect 0.26 (95% CI: 0.11-0.41), P = 0.001; total effect 0.26 (95% CI: 0.11-0.42), P = 0.001] and estimated fetal weight [direct effect 0.22 (95% CI: 0.08-0.35), P = 0.002; total effect 0.22 (95% CI: 0.08-0.35), P = 0.002], with no evidence of mediation by treated gestational diabetes. There was no apparent association between maternal BMI and fetal adiposity measures, or mediation by treated gestational diabetes.

CONCLUSIONS

We show an important association between increased maternal BMI and fetal growth, not mediated by treated gestational diabetes. There was no association between increased maternal BMI and fetal adiposity measures, or mediation by treated gestational diabetes. Whether these findings represent 'saturation' in the effect of maternal BMI on fetal growth or the effect of treatment of GDM is unclear.

FUNDING

This project was funded by a 4-year project grant from the National Health and Medical Research Council (NHMRC), Australia (ID 519240); The Channel 7 Children's Research Foundation, South Australia; and the US National Institutes of Health (R01 HL094235-01).

TWEETABLE ABSTRACT

Increased fetal growth associated with maternal obesity is not mediated by gestational diabetes.

Increased fetal adiposity prior to diagnosis of gestational diabetes in South Asians: more evidence for the 'thin-fat' baby

AIMS/HYPOTHESIS

Gestational diabetes mellitus (GDM) is associated with an increased future risk of obesity in the offspring. Increased adiposity has been observed in the newborns of women with GDM. Our aim was to examine early fetal adiposity in women with GDM.

METHODS

Obstetric and sonographic data was collated for 153 women with GDM and 178 controls from a single centre in Chennai, India. Fetal head circumference (HC), abdominal circumference (AC), femur length (FL) and biparietal diameter (BPD) were recorded at 11, 20 and 32 weeks. Anterior abdominal wall thickness (AAWT) as a marker of abdominal adiposity at 20 and 32 weeks was compared between groups. Adjustments were made for maternal age, BMI, parity, gestational weight gain, fetal sex and gestational age.

RESULTS

Fetuses of women with GDM had significantly higher AAWT at 20 weeks (β 0.26 [95% CI 0.15, 0.37] mm, p < 0.0001) despite lower measures of HC, FL, BPD and AC. AAWT remained higher in the fetuses of women with GDM at 32 weeks (β 0.48 [0.30, 0.65] mm, p < 0.0001) despite similar measures for HC, FL, BPD and AC between groups. Both groups had similar birthweights at term. There was an independent relationship between fasting plasma glucose levels and AAWT after adjustment as described above.

CONCLUSIONS/INTERPRETATION

A 'thin but fat' phenotype signifying a disproportionate increase in adiposity despite smaller or similar lean body mass was observed in the fetuses of mothers with GDM, even at 20 weeks, thus pre-dating the biochemical diagnosis of GDM. Increased AAWT may serve as an early marker of GDM.