Transvaginal ultrasonography in women receiving emergency contraception

To determine whether transvaginal ultrasonography improves evaluation of conception time in women seeking emergency contraception. Prospective study. Obstetrics and Gynecology Department, Siena University, Siena, Italy. One hundred sixty-three women seeking postcoital contraception. Data on menstrual history and time of unprotected intercourse were recorded. Ultrasonographic variables evaluated were ovarian follicle or corpus luteum diameter, endometrial echopattern and thickness, and peritoneal fluid volume. Expected pregnancy rates were calculated according to the probability of conception as estimated from Dixon’s table of data, based solely on anamnestic data, or from endometrial or ovarian findings on transvaginal ultrasonography. According to the menstrual history (cut-off level < 0.03) we expected to find 7.6 pregnancies (7.9 in the high-risk group and 0.31 in the low-risk group). According to transvaginal ultrasonography (at the same cut-off), we expected 11.2 pregnancies (0.3 in the low-risk group and 10.9 in the high-risk group). No more than 7 pregnancies were observed, all of which occurred in the high-risk group as determined by transvaginal ultrasonography. In contrast, on the basis of anamnestic data, 4 of 7 pregnancies were in the high-risk group and 3 of 7 were in the low-risk group. Transvaginal ultrasonography allows timely definition of the fertile period and is a reliable method of computing the day of ovulation. It improves therapeutic options by allowing treatment of only women at high risk of conception.