Gestational Age at Arrest of Development: An Alternative Approach for Assigning Time at Risk in Studies of Time-Varying Exposures and Miscarriage.

Gestational Age at Arrest of Development: An Alternative Approach for Assigning Time at Risk in Studies of Time-Varying Exposures and Miscarriage. Am J Epidemiol. 2018 Dec 06;: Authors: Sundermann AC, Mukherjee S, Wu P, Velez Edwards DR, Hartmann KE Abstract Time between arrest of pregnancy development and miscarriage represents a window in which pregnancy is nonviable and not developing. In effect, the loss has happened and exposures cannot influence its fate. However, epidemiologic studies of miscarriage traditionally use gestational age at miscarriage to assign time in survival analyses, which overestimates duration of exposure and time at risk. In the Right from the Start pregnancy cohort (2000-2012), we characterized the gap between estimated gestational age at arrest of development (GAAD) and miscarriage using transvaginal ultrasound in 500 women recruited from 3 states (North Carolina, Tennessee, and Texas). We compare effect estimates from models using GAAD versus gestational age at miscarriage to assign time at risk through a simulation study of 4 exposure patterns with varying effect sizes. The median gap between GAAD and miscarriage was 23 days (inter-quartile range 15-32 days). Use of GAAD decreased bias and variance of the estimated association for time-varying exposures, whereas half the time using gestational age at miscarriage led to estimates that differed from the true effect by more than 20%. Using GAAD to assign t...
Source: Am J Epidemiol - Category: Epidemiology Authors: Tags: Am J Epidemiol Source Type: research