Does a retrospective cohort study of implanted medical devices and selected chronic diseases in Medicare claim data?
For the most part, our study confirms our previous case-control results. Although confounding by presurgical conditions (such as diabetes) remains a plausible explanation of the findings, several associations are worthy of more detailed research.
Fetal size in the second trimester is a determinant of birth weight and pregnancy duration, small fetuses having lower birth weights and longer pregnancies (up to 13 days compared with large fetuses). Our results support a concept of individually assigned pregnancy duration according to growth rates rather than imposing a standard of 280-282 days on all pregnancies.