A preliminary report on the incidence of clinical and subclinical spontaneous pregnancy loss

The preliminary purpose of this study was to document the incidence of clinical and subclinical spontaneous abortion in women who have no reproductive capability impairment. The relationship between prior oral contraception use and a subsequent increased incidence of spontaneous subclinical abortion was investigated. the incidence of clinically apparent spontaneous abortion ranges from 8.3 percent to 15 percent. Since factors such as increasing maternal age, prior spontaneous abortion, there is no "normal" incidence of abortion that applies to all women. Abortion risk increases with advancing maternal age, particularly after age 35 and especially over age 40. A history of prior spontaneous abortion increases the risk of subsequent spontaneous abortion, especially if the first abortion was associated with a normal karyotype. The effects of increasing gravidity are controversial; some investigators claim this factor constitutes an increasing risk for spontaneous abortion; others dispute the relevance of gravidity.