Bodnar Lisa M, Abrams Barbara, Siminerio Lara, Lash Timothy L
Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Department of Obstetrics, Gynecology, and Reproductive Sciences, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Matern Child Nutr. 2016 Jul;12(3):632-8. doi: 10.1111/mcn.12160. Epub 2014 Dec 17.
Birth certificates are an important source of pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) data for surveillance and aetiologic studies, but little is known about their validity in twin pregnancies. Twins experience high rates of adverse perinatal outcomes that have been associated with BMI and GWG in singletons. Our objective was to evaluate the accuracy of birth certificate-derived pre-pregnancy BMI and GWG compared with medical record-derived data in a sample of 186 twin pregnancies at a teaching hospital in Pennsylvania (2003-2010). Twelve strata were created by simultaneous stratification on pre-pregnancy BMI (underweight, normal weight/overweight, obese class 1, obese classes 2 and 3) and GWG (<20th, 20-80th, >80th percentile). The agreement of birth certificate-derived pre-pregnancy BMI category with medical record BMI category was lowest among underweight mothers [75% (95% confidence interval 51-91%) ] and highest among normal/overweight [97% (90-99%) ] and obese classes 2 and 3 mothers [97% (85-99%) ]. Agreement for GWG category from the birth certificate varied from 57% (41-70%) for GWG >80th percentile to 80% (65-91%) and 82% (72-89%) for GWG <20th and 20th-80th percentiles, respectively. The misclassification of BMI and GWG was primarily due to error in pre-pregnancy weight rather than weight at delivery or height. Agreement proportions for twins were not meaningfully different from the proportions in a comparable sample of singleton pregnancies. These data suggest that birth certificate-based BMI and GWG data are prone to error in twin pregnancies. Those who use these data should conduct internal validation studies and adjust their results using bias analyses.
出生证明是用于监测和病因学研究的孕前体重指数（BMI）和孕期体重增加（GWG）数据的重要来源，但对于其在双胎妊娠中的有效性知之甚少。双胎妊娠的围产期不良结局发生率较高，这些结局与单胎妊娠中的BMI和GWG有关。我们的目的是在宾夕法尼亚州一家教学医院的186例双胎妊娠样本（2003 - 2010年）中，评估出生证明得出的孕前BMI和GWG与病历得出的数据相比的准确性。通过对孕前BMI（体重过轻、正常体重/超重、肥胖1级、肥胖2级和3级）和GWG（<第20百分位数、第20 - 80百分位数、>第80百分位数）同时分层创建了12个层次。出生证明得出的孕前BMI类别与病历BMI类别的一致性在体重过轻的母亲中最低[75%（95%置信区间51 - 91%）]，在正常/超重母亲[97%（90 - 99%）]以及肥胖2级和3级母亲[97%（85 - 99%）]中最高。出生证明中GWG类别的一致性在GWG >第80百分位数时为57%（41 - 70%），在GWG <第20百分位数和第20 - 80百分位数时分别为80%（65 - 91%）和82%（72 - 89%）。BMI和GWG的错误分类主要是由于孕前体重的误差，而非分娩时体重或身高的误差。双胎妊娠的一致性比例与单胎妊娠可比样本中的比例没有显著差异。这些数据表明，基于出生证明的BMI和GWG数据在双胎妊娠中容易出错。使用这些数据的人应进行内部验证研究，并使用偏差分析调整其结果。
