Comparison of analyses among live births, live births and stillbirths, and all survival outcomes for selected exposures and birth defects; National Birth Defects Prevention Study, 1997 – 2011.
Estimates were obtained from Firth’s logistic regression models with profile likelihood 95% confidence intervals adjusted for maternal age category, race/ethnicity, and first trimester exposure to a vitamin containing folic acid. The reference line indicates the null value. Birth defects are arranged in order of prevalence of stillbirth and termination from highest (top) to lowest (bottom). Exposures are arranged from (left) lowest association with prevalence of stillbirth and termination to (right) highest. If multiple fetuses in a multifetal pregnancy had eligible birth defects the oldest fetus was selected for inclusion.
a The 95% CI among live births only (3.16, 7.20) excludes the point estimate among all survival outcomes (live births, stillbirths, and terminations; 2.44) and slightly overlaps the upper bound of the 95% confidence interval for the latter model (1.73, 3.35).