Sonographic assessment of the incompetent cervix in pregnancy.

Ultrasonography (US) was done in 40 women with a history of recurrent midtrimester abortion. The results were compared with those of a control group who consisted of 53 women with no previous history of abortion and had had at least one full term pregnancy with normal vaginal delivery. Mean internal cervical os diameters of 16.0 mm and 22.5 mm at 10 and 27 weeks gestation respectively were recorded in the cervical incompetent patients while mean values of 7.7 mm and 14.5 mm at 13 and 28 weeks gestation were observed in the normal control subjects. Full analysis of covariance showed statistically significant difference in the internal os diameter between the control group and the cervical incompetence cases (t90 = 9.33, P less than 0.001).