Abstract:
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We investigate the causal effects of etanercept on birth defects, which raise attention as the proportion of liveborn infants with major birth defects was higher for women exposed to etanercept compared to diseased etanercept unexposed women. An outstanding problem is the missing birth defect outcomes due to spontaneous abortion since in accepted standard practice an infant or a fetus is assumed not to be malformed unless a defect is found. This led to likely bias (and missing not at random) because, according to the theory of “terathanasia”, a defected fetus is more likely to be spontaneously aborted. In this paper we aim to estimate and provide inference for the causal parameters of scientific interest, including the principal effects, making use of the missing data mechanism informed by terathanasia. During the process we also deal with complications in the data including left truncation, observational nature, and rare events. We report our findings which not only provide a more in-depth analysis than previously done on etanercept, but also shed light on how similar studies on causal effects of medication (or vaccine, other substances etc.) during pregnancy may be analyzed.
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