The vanishing fetus. A report of 17 cases of triplets and quadruplets.

The incidence of multiple conceptions is higher than the incidence of multiple deliveries. The "vanishing fetus" is a relatively new concept being a direct result of the advent of ultrasonography. Early first trimester loss of one or more conceptuses accounts for this phenomenon. The patient may be symptomatic (bleeding, pain, abdominal cramps) but in most instances, the finding is fortuitous. We report 17 cases of a vanishing fetus in a multiple gestation of greater than twins. In 13 patients one fetus vanished in the course of pregnancy while in four cases two fetuses disappeared from each gestation. The phenomenon was observed up to the 16th week of pregnancy. It is our feeling that the finding of a vanishing fetus should be recorded early, as the prognosis for pregnancy bleeding is different than in the singleton pregnancy. Thus information regarding this phenomenon should be given to couples who consider artificial reduction of fetuses in the multiple gestation.