Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA.
Division of Epidemiology, School of Public Health, University of California Berkeley, Berkeley, CA, USA.
Paediatr Perinat Epidemiol. 2020 Sep;34(5):618-627. doi: 10.1111/ppe.12667. Epub 2020 Mar 17.
Using ICD-9 codes underestimates the prevalence of obesity in adults; however, the validity of these codes in studies of pregnancy-related outcomes is not known.
To compare classification of maternal obesity based on ICD-9 codes in hospital discharge records versus data from birth certificates in the same women, examine predictors of agreement, and assess how associations between obesity and two birth outcomes differ by source of weight data.
This population-based study included 2 329 145 California births between 2007 and 2012. We compared data on obesity from childbirth hospital discharge records (ICD-9 codes for obesity) and birth certificates (pre-pregnancy body mass index (BMI) calculated from weight and height) and identified predictors of agreement between the two sources. Logistic regression models assessed whether the two definitions of obesity resulted in different estimates of the associations of obesity with caesarean birth and large-for-gestational age.
Overall, 464 754 women (20.0%) had obesity based on their pre-pregnancy BMI while only 100 002 (4.3%) had an obesity-related ICD-9 code. The sensitivity of ICD-9-based obesity was low at 16.2%; however, obesity codes were highly specific at 98.7%, with a negative predictive value of 82.5% and a positive predictive value of 75.2%. Among women with obesity identified by the birth certificate, those with pre-pregnancy and pregnancy-related complications (eg diabetes and hypertension) were more likely to have an obesity-related diagnosis in their delivery hospital discharge record. Using ICD-9 codes overestimated the association of obesity with caesarean birth and newborn large-for-gestational age.
ICD-9 codes in childbirth discharge records captured only one in five women with pre-pregnancy obesity. Sensitivity varied by maternal characteristics and conditions. This misclassification resulted in bias when examining the association of obesity and pregnancy-related outcomes.
使用 ICD-9 代码会低估成年人肥胖的患病率；然而，这些代码在与妊娠相关结局的研究中的有效性尚不清楚。
比较基于医院出院记录中 ICD-9 代码的产妇肥胖分类与同一妇女的出生证明数据，研究一致性的预测因素，并评估肥胖与两种出生结局之间的关联因体重数据来源的不同而有何差异。
本研究为基于人群的研究，共纳入 2007 年至 2012 年期间加利福尼亚州的 2329145 例分娩。我们比较了来自分娩医院出院记录（肥胖的 ICD-9 代码）和出生证明（从体重和身高计算得出的孕前体重指数（BMI））的肥胖数据，并确定了两种来源之间一致性的预测因素。Logistic 回归模型评估了肥胖的两种定义是否导致肥胖与剖宫产分娩和大于胎龄儿之间关联的估计值存在差异。
总体而言，464754 名妇女（20.0%）根据孕前 BMI 被诊断为肥胖，而仅有 100002 名妇女（4.3%）存在与肥胖相关的 ICD-9 编码。ICD-9 编码肥胖的灵敏度较低，为 16.2%；然而，肥胖编码的特异性很高，为 98.7%，阴性预测值为 82.5%，阳性预测值为 75.2%。在出生证明诊断为肥胖的妇女中，那些患有孕前和妊娠相关并发症（如糖尿病和高血压）的妇女在分娩医院出院记录中更有可能被诊断为肥胖相关疾病。使用 ICD-9 编码会高估肥胖与剖宫产分娩和新生儿大于胎龄儿之间的关联。
分娩出院记录中的 ICD-9 编码仅捕捉到五分之一有孕前肥胖的妇女。灵敏度因产妇特征和状况而异。这种错误分类会导致在检查肥胖与妊娠相关结局之间的关联时产生偏差。
