妊娠期间合理饮食和运动可能减少超重肥胖、剖宫产、妊娠糖尿病
营养不良包括营养不足和营养过剩（超重或肥胖）。妊娠期间的超重或肥胖，可使母婴在妊娠期间以及后续生活均处于风险之中，这对医疗和社会造成很大影响。
2017年7月19日，《英国医学杂志》在线发表国际妊娠体重管理协作组（i-WIP）随机研究个体参与者数据荟萃分析：妊娠期间饮食和体力活动干预对妊娠体重增加和妊娠结局的影响。
个体参与者数据的荟萃分析从统计学和临床上都比集合数据的荟萃分析有更多潜在的优势。集合数据往往不可得到，报告拙劣，对不同研究的来源和表述也相去甚远（例如，比值比和相对风险的比较），而且更倾向报告（并且更加详细）那些在统计学或临床上呈显著性的结果，因此增加了发表偏倚和研究内选择性报告的风险。与此相反，个体参与者数据使不同研究间的标准化分析变得容易，可以直接提取期望的信息，促进显著性的独立以及如何进行报告。个体参与者数据也比原始发表的文章有更长随访时间、更多参与者、更多结局。当然，工作量也非常庞大。
该研究对主要电子数据库从建库至2017年2月的个体参与者数据（对语言无限制），选择妊娠期间干预饮食和体力活动的随机研究，根据年龄、妊娠史、种族、体重指数、现有医疗条件分组，进行系统回顾和荟萃分析。
干预包括获得营养师咨询、特定产前课程，以提供饮食和生活方式的建议，或进行中等强度的体力活动（例如有氧运动）。
结果筛选出符合要求的36项随机研究共12526位女性的个体参与者数据。
干预组与对照组相比，体重增加较少（平均差：-0.70kg，95%置信区间：-0.92～-0.48kg，I²：14.1%；根据33项研究，9320位女性）。
虽然汇总影响评估有利于干预，但是母亲、后代的复合结局差异无统计学意义（比值比：0.90、0.94，95%置信区间：0.79～1.03、0.83～1.08，I²：26.7%、0%；根据24、18项研究，8852、7981位女性）。无证据表明亚组之间的干预影响存在差异，无论对于妊娠体重增加或复合结局，即使年龄、妊娠史、种族、体重指数、现有医疗条件存在差异。
强有力的证据表明，干预使剖宫产显著减少9%（比值比：0.91，95%置信区间：0.83～0.99，I²：0%；根据32项研究，11410位女性），但是个体参与者数据荟萃分析未见对其他个体并发症有显著影响。
当个体参与者数据加入未提供个体参与者数据研究的研究水平数据时，总体影响相似，并可使妊娠糖尿病显著减少24%（比值比：0.76，95%置信区间：0.65～0.89，I²=36.8%；59项研究，16885位女性）的证据较强。
因此，妊娠期间干预饮食和体力活动可能减少体重增加、降低剖宫产率、减少妊娠糖尿病。无证据表明，女性亚组之间的影响存在差异。不过，该研究也存在一些局限性，包括参与者大多为白人、教育程度中到高等，这是一个有利于干预依从性的因素。
对此，牛津大学、布里斯托大学的围产期流行病专家、公共卫生专家、运动与营养专家发表同期评论：妊娠期间饮食和锻炼的生活方式干预安全并有助于控制体重增加。
BMJ. 2017 Jul 19;358:j3119.
Effect of diet and physical activity based interventions in pregnancy on gestational weight gain and pregnancy outcomes: meta-analysis of individual participant data from randomised trials.
International Weight Management in Pregnancy (i-WIP) Collaborative Group.
OBJECTIVE: To synthesise the evidence on the overall and differential effects of interventions based on diet and physical activity during pregnancy, primarily on gestational weight gain and maternal and offspring composite outcomes, according to women's body mass index, age, parity, ethnicity, and pre-existing medical condition; and secondarily on individual complications.
DESIGN: Systematic review and meta-analysis of individual participant data (IPD).
DATA SOURCES: Major electronic databases from inception to February 2017 without language restrictions.
ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomised trials on diet and physical activity based interventions in pregnancy.
DATA SYNTHESIS: Statistical models accounted for clustering of participants within trials and heterogeneity across trials leading to summary mean differences or odds ratios with 95% confidence intervals for the effects overall, and in subgroups (interactions).
RESULTS: IPD were obtained from 36 randomised trials (12 526 women). Less weight gain occurred in the intervention group than control group (mean difference -0.70 kg, 95% confidence interval -0.92 to -0.48 kg, I2=14.1%; 33 studies, 9320 women). Although summary effect estimates favoured the intervention, the reductions in maternal (odds ratio 0.90, 95% confidence interval 0.79 to 1.03, I2=26.7%; 24 studies, 8852 women) and offspring (0.94, 0.83 to 1.08, I2=0%; 18 studies, 7981 women) composite outcomes were not statistically significant. No evidence was found of differential intervention effects across subgroups, for either gestational weight gain or composite outcomes. There was strong evidence that interventions reduced the odds of caesarean section (0.91, 0.83 to 0.99, I2=0%; 32 studies, 11 410 women), but not for other individual complications in IPD meta-analysis. When IPD were supplemented with study level data from studies that did not provide IPD, the overall effect was similar, with stronger evidence of benefit for gestational diabetes (0.76, 0.65 to 0.89, I2=36.8%; 59 studies, 16 885 women).
CONCLUSION: Diet and physical activity based interventions during pregnancy reduce gestational weight gain and lower the odds of caesarean section. There is no evidence that effects differ across subgroups of women.
PMID: 28724518
DOI: 10.1136/bmj.j3119
BMJ. 2017 Jul 19;358:j3283.
Diet and exercise in pregnancy: Lifestyle interventions are safe in pregnancy, and help control weight gain.
Knight M, Foster C.
National Perinatal Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK; Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, Faculty of Social Sciences and Law, University of Bristol, Bristol, UK.
PMID: 28724550
DOI: 10.1136/bmj.j3283