Quiz Ref ID Excessive and insufficient gestational weight gain have been associated with adverse pregnancy outcomes, including small for gestational age (SGA), large for gestational age (LGA), macrosomia, cesarean delivery, gestational diabetes mellitus (GDM), preeclampsia, postpartum weight retention, and offspring obesity.^1-4 The Institute of Medicine (IOM; now known as the National Academy of Medicine) recommendations regarding gestational weight gain were developed in 1990 to guide clinical practice.⁵ These aimed to reduce the incidence of low-birth-weight babies and were based on a 1980 National Natality Survey of a largely white population. The updated IOM guidelines in 2009⁶ incorporated World Health Organization (WHO) categories of maternal body mass index (BMI; calculated as weight in kilograms divided by height in meters squared; BMI for underweight, <18.5; normal weight, 18.5-24.9; overweight, 25-29.9; and obese, ≥30)⁷ and recommended less gestational weight gain for obese women (Table 1). The 2009 guidelines identified maternal and infant relationships with gestational weight gain but were based on lower general population BMI with limited ethnic diversity. The 2009 IOM guidelines are endorsed by the American College of Obstetricians and Gynecologists, although they are not universally implemented.⁸

The association between Institute of Medicine (IOM) guidelines and pregnancy outcomes across ethnicities is uncertain. We evaluated the associations of gestational weight gain (GWG) outside 2009 IOM guidelines, with maternal and infant outcomes across the USA, western Europe and east Asia, with subgroup analyses in Asia. The aim was to explore ethnic differences in maternal prepregnancy body mass index (BMI), GWG and health outcomes across these regions. Systematic review, meta-analysis and meta-regression of observational studies were used for the study. MEDLINE, MEDLINE In-Process, Embase and all Evidence-Based Medicine (EBM) Reviews were searched from 1999 to 2017. Studies were stratified by prepregnancy BMI category and total pregnancy GWG. Odds ratio (ORs) 95% confidence intervals (CI) applied recommended GWG within each BMI category as the reference. Primary outcomes were small for gestational age (SGA), preterm birth and large for gestational age (LGA). Secondary outcomes were macrosomia, caesarean section and gestational diabetes. Overall, 5874 studies were identified and 23 were included (n = 1,309,136). Prepregnancy overweight/obesity in the USA, Europe and Asia was measured at 42%, 30% and 10% respectively, with underweight 5%, 3% and 17%. GWG below guidelines in the USA, Europe and Asia was 21%, 18% and 31%, and above was 51%, 51% and 37% respectively. Applying regional BMI categories in Asia showed GWG above guidelines (51%) was similar to that in the USA and Europe. GWG below guidelines was associated with a higher risk of SGA (USA/Europe [OR 1.51; CI 1.39, 1.63]; Asia [1.63; 1.45, 1.82]) and preterm birth (USA/Europe [1.35; 1.17, 1.56]; Asia [1.06; 0.78, 1.44]) than GWG within guidelines. GWG above guidelines was associated with a higher risk of LGA (USA/Europe [1.93; 1.81, 2.06]; Asia [1.68; 1.51 , 1.87]), macrosomia (USA/Europe [1.87; 1.70, 2.06]; Asia [2.18; 1.91, 2.49]) and caesarean (USA/Europe [1.26; 1.21, 1.33]; Asia [1.37; 1.30, 1.45]). Risks remained elevated when regional BMI categories were applied for GWG recommendations. More women in Asia were categorised as having GWG below guidelines using World Health Organization (WHO) (60%) compared to regional BMI categories (16%), yet WHO BMI was not accompanied by increased risks of adverse outcomes. Women in the USA and western Europe have higher prepregnancy BMI and higher rates of GWG above guidelines than women in east Asia. However, when using regional BMI categories in east Asia, rates of GWG above guidelines are similar across the three continents. GWG outside guidelines is associated with adverse outcomes across all regions. If regional BMI categories are used in east Asia, IOM guidelines are applicable in the USA, western Europe and east Asia.

Background: Diet- and physical activity-based interventions in pregnancy have the potential to alter maternal and child outcomes.Objectives: To assess whether or not the effects of diet and lifestyle interventions vary in subgroups of women, based on maternal body mass index (BMI), age, parity, Caucasian ethnicity and underlying medical condition(s), by undertaking an individual patient data (IPD) meta-analysis. We also evaluated the association of gestational weight gain (GWG) with adverse pregnancy outcomes and assessed the cost-effectiveness of the interventions.Data sources: MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects and Health Technology Assessment database were searched from October 2013 to March 2015 (to update a previous search).Review methods: Researchers from the International Weight Management in Pregnancy Collaborative Network shared the primary data. For each intervention type and outcome, we performed a two-step IPD random-effects meta-analysis, for all women (except underweight) combined and for each subgroup of interest, to obtain summary estimates of effects and 95% confidence intervals (CIs), and synthesised the differences in effects between subgroups. In the first stage, we fitted a linear regression adjusted for baseline (for continuous outcomes) or a logistic regression model (for binary outcomes) in each study separately; estimates were combined across studies using random-effects meta-analysis models. We quantified the relationship between weight gain and complications, and undertook a decision-analytic model-based economic evaluation to assess the cost-effectiveness of the interventions.Results: Diet and lifestyle interventions reduced GWG by an average of 0.70 kg (95% CI –0.92 to –0.48 kg; 33 studies, 9320 women). The effects on composite maternal outcome [summary odds ratio (OR) 0.90, 95% CI 0.79 to 1.03; 24 studies, 8852 women] and composite fetal/neonatal outcome (summary OR 0.94, 95% CI 0.83 to 1.08; 18 studies, 7981 women) were not significant. The effect did not vary with baseline BMI, age, ethnicity, parity or underlying medical conditions for GWG, and composite maternal and fetal outcomes. Lifestyle interventions reduce Caesarean sections (OR 0.91, 95% CI 0.83 to 0.99), but not other individual maternal outcomes such as gestational diabetes mellitus (OR 0.89, 95% CI 0.72 to 1.10), pre-eclampsia or pregnancy-induced hypertension (OR 0.95, 95% CI 0.78 to 1.16) and preterm birth (OR 0.94, 95% CI 0.78 to 1.13). There was no significant effect on fetal outcomes. The interventions were not cost-effective. GWG, including adherence to the Institute of Medicine-recommended targets, was not associated with a reduction in complications. Predictors of GWG were maternal age (summary estimate –0.10 kg, 95% CI –0.14 to –0.06 kg) and multiparity (summary estimate –0.73 kg, 95% CI –1.24 to –0.23 kg).Limitations: The findings were limited by the lack of standardisation in the components of intervention, residual heterogeneity in effects across studies for most analyses and the unavailability of IPD in some studies.Conclusion: Diet and lifestyle interventions in pregnancy are clinically effective in reducing GWG irrespective of risk factors, with no effects on composite maternal and fetal outcomes.Future work: The differential effects of lifestyle interventions on individual pregnancy outcomes need evaluation.Study registration: This study is registered as PROSPERO CRD42013003804.Funding: The National Institute for Health Research Health Technology Assessment programme.

Variations in intervention rates, without subsequent reductions in adverse outcomes, can indicate overuse. We studied variations in and associations between commonly used childbirth interventions and adverse outcomes, adjusted for population characteristics. In this multinational cross-sectional study, existing data on 4,729,307 singleton births at ≥37 weeks in 2013 from Finland, Sweden, Norway, Denmark, Iceland, Ireland, England, the Netherlands, Belgium, Germany (Hesse), Malta, the United States, and Chile were used to describe variations in childbirth interventions and outcomes. Numbers of births ranged from 3,987 for Iceland to 3,500,397 for the USA. Crude data were analysed in the Netherlands, or analysed data were shared with the principal investigator. Strict variable definitions were used and information on data quality was collected. Intervention rates were described for each country and stratified by parity. Uni- and multivariable analyses were performed, adjusted for population characteristics, and associations between rates of interventions, population characteristics, and outcomes were assessed using Spearman’s rank correlation coefficients. Considerable intercountry variations were found for all interventions, despite adjustments for population characteristics. Adjustments for ethnicity and body mass index changed odds ratios for augmentation of labour and episiotomy. Largest variations were found for augmentation of labour, pain relief, episiotomy, instrumental birth, and cesarean section (CS). Percentages of births at ≥42 weeks varied from 0.1% to 6.7%. Rates among nulliparous versus multiparous women varied from 56% to 80% versus 51% to 82% for spontaneous onset of labour; 14% to 36% versus 8% to 28% for induction of labour; 3% to 13% versus 7% to 26% for prelabour CS; 16% to 48% versus 12% to 50% for overall CS; 22% to 71% versus 7% to 38% for augmentation of labour; 50% to 93% versus 25% to 86% for any intrapartum pain relief, 19% to 83% versus 10% to 64% for epidural anaesthesia; 6% to 68% versus 2% to 30% for episiotomy in vaginal births; 3% to 30% versus 1% to 7% for instrumental vaginal births; and 42% to 70% versus 50% to 84% for spontaneous vaginal births. Countries with higher rates of births at ≥42 weeks had higher rates of births with a spontaneous onset (rho = 0.82 for nulliparous/rho = 0.83 for multiparous women) and instrumental (rho = 0.67) and spontaneous (rho = 0.66) vaginal births among multiparous women and lower rates of induction of labour (rho = −0.71/−0.66), prelabour CS (rho = −0.61/−0.65), overall CS (rho = −0.61/−0.67), and episiotomy (multiparous: rho = −0.67). Variation in CS rates was mainly due to prelabour CS (rho = 0.96). Countries with higher rates of births with a spontaneous onset had lower rates of emergency CS (nulliparous: rho = −0.62) and higher rates of spontaneous vaginal births (multiparous: rho = 0.70). Prelabour and emergency CS were positively correlated (nulliparous: rho = 0.74). Higher rates of obstetric anal sphincter injury following vaginal birth were found in countries with higher rates of spontaneous birth (nulliparous: rho = 0.65). In countries with higher rates of epidural anaesthesia (nulliparous) and spontaneous births (multiparous), higher rates of Apgar score < 7 were found (rhos = 0.64). No statistically significant variation was found for perinatal mortality. Main limitations were varying quality of data and missing information. Considerable intercountry variations were found for all interventions, even after adjusting for population characteristics, indicating overuse of interventions in some countries. Multivariable analyses are essential when comparing intercountry rates. Implementation of evidence-based guidelines is crucial in optimising intervention use and improving quality of maternity care worldwide.