Response to Harcombe

The crux of Dr. Harcombe’s critique is her assertion that our study design was inappropriate for our research objective, which was to investigate whether maternal carbohydrate restriction before conception was associated with neural tube defects (NTDs) in the National Birth Defects Prevention Study (NBDPS), a population-based case-control study of birth defects (Desrosiers, Siega-Riz, Mosley, Meyer, & The National Birth Defects Prevention Study, 2018). In her Letter, Dr. Harcombe claims that our study is fundamentally flawed because “cases should have been women who restrict carbohydrates and the controls should have been women who don’t and the outcome measure should have been NTD-affected pregnancies.” Despite her confusing (mis)use of the terms case and control, what Dr. Harcombe appears to be describing is a cohort study.