From the aCenter for Clinical Epidemiology, Lady Davis Institute, Jewish General Hospital, Montreal, QC, Canada; bDepartment of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, QC, Canada; cDepartment of Pediatrics, McGill University, Montreal, QC, Canada; and dDepartment of Medicine, McGill University, Montreal, QC, Canada.
Epidemiology. 2017 Nov;28(6):854-862. doi: 10.1097/EDE.0000000000000713.
Studies on the safety of prenatal medication use require valid estimation of the pregnancy duration. However, gestational age is often incompletely recorded in administrative and clinical databases. Our objective was to compare different approaches to estimating the pregnancy duration.
Using data from the Clinical Practice Research Datalink and Hospital Episode Statistics, we examined the following four approaches to estimating missing gestational age: (1) generalized estimating equations for longitudinal data; (2) multiple imputation; (3) estimation based on fetal birth weight and sex; and (4) conventional approaches that assigned a fixed value (39 weeks for all or 39 weeks for full term and 35 weeks for preterm). The gestational age recorded in Hospital Episode Statistics was considered the gold standard. We conducted a simulation study comparing the described approaches in terms of estimated bias and mean square error.
A total of 25,929 infants from 22,774 mothers were included in our "gold standard" cohort. The smallest average absolute bias was observed for the generalized estimating equation that included birth weight, while the largest absolute bias occurred when assigning 39-week gestation to all those with missing values. The smallest mean square errors were detected with generalized estimating equations while multiple imputation had the highest mean square errors.
The use of generalized estimating equations resulted in the most accurate estimation of missing gestational age when birth weight information was available. In the absence of birth weight, assignment of fixed gestational age based on term/preterm status may be the optimal approach.
产前药物使用安全性的研究需要对妊娠周期进行有效的评估。然而，在行政和临床数据库中，妊娠周期往往记录不完整。我们的目标是比较不同的方法来估计妊娠周期。
使用来自临床实践研究数据链接和医院入院统计数据库的数据，我们研究了以下四种方法来估计缺失的妊娠周期：（1）纵向数据的广义估计方程；（2）多重插补；（3）基于胎儿出生体重和性别估计；（4）传统方法，即分配固定值（所有为 39 周，足期为 39 周，早产为 35 周）。医院入院统计记录的妊娠周期被认为是金标准。我们进行了一项模拟研究，比较了这些方法在估计偏差和均方误差方面的表现。
共有 25929 名婴儿来自 22774 名母亲，被纳入我们的“金标准”队列。当纳入出生体重时，广义估计方程的平均绝对偏差最小，而当所有缺失值均分配 39 周妊娠周期时，平均绝对偏差最大。当使用广义估计方程时，均方误差最小，而多重插补的均方误差最大。
当有出生体重信息时，使用广义估计方程可以最准确地估计缺失的妊娠周期。在没有出生体重信息的情况下，根据足月/早产状态分配固定的妊娠周期可能是最佳方法。
