The roles of oligomenorrhoea and fetal chromosomal abnormalities in spontaneous abortions.

The pathogenesis of spontaneous abortions, other than fetal chromosomal abnormalities, is not fully understood. We examined the incidence of oligomenorrhoea in relation to fetal chromosomal analyses and ultrasonographic examination in women who aborted spontaneously. The data demonstrated that the incidence of oligomenorrhoea was higher in women with normal fetal karyotyped abortions, especially normal karyotyped anembryonic pregnancies, than in those with abnormal karyotyped abortions (34.0 versus 12.5%, P < 0.01). Furthermore, the incidence of oligomenorrhoea was inversely correlated with fetal size exclusively in abortions with normal fetal karyotypes. It is suggested that oligomenorrhoea, i.e. delayed ovulation, itself may be closely associated with sporadic spontaneous abortion.