Question

An investigator examined cases of fetal death in 27,000 cases and classified mothers according to whether they had experienced sexual intercourse within 1 month before delivery. It was found that 11% of the mothers of fetuses that died and 2.5% of the fetuses that survived had had sexual intercourse during the period. It was concluded that that sexual intercourse during the month preceding delivery caused the fetal deaths. What guideline(s) did this researcher fail to take in to account? Why is the conclusion reached by the investigator incorrect?

Answer 1

1. May be incorrect because mothers who had intercourse during the month before the chirldbirth may differ in other important characteristics from those who did not.

2. May be incorrect because prevelance rates are used where incidence rates are needed.