The assessment of the gestational sac diameter, crown–rump length, progesterone and fetal heart rate measurements at the 10th gestational week to predict the spontaneous abortion risk M. Metin Altay, Hakan Yaz and Ali Haberal Ankara Etlik Maternity and Women’s Health Academic and Research Hospital, Ankara, Turkey Abstract Aim: The assessment of the first trimester ultrasonographic and progesterone measurements to predict spon- taneous abortion risk. Methods: Ninety-nine women at the 10th week of pregnancy were included in this prospective study. Their ages, progesterone (P) levels, mean gestational sac diameters (MGSD), crown–rump lengths (CRL), MGSD– CRL measurements and fetal heart rates (FHR) were recorded. These variables were compared by abortion status. Results: Patients were followed up until the 20th weeks, and 8 (8.08%) aborted. We evaluated the variables by receiver operator characteristic curve to predict abortion. Only the areas under the curve for P levels (0.29) and for MGSD–CRL (0.16) were statistically significant. We also made logistic regression analysis to predict abortion. P level and FHR were statistically significant (P < 0.01) when the threshold value was 50%. Negative predictive value of the model was 98.9%, and positive predictive value was 50%. Overall, this model can correctly classify 94.9% of the groups. We determined threshold values for MGSD–CRL (10 mm) and P (25 ng/mL) to predict abortion, but not for FHR. Interestingly, 14 patients with FHR  175 beats/min did not abort. For the MGSD–CRL threshold, we can predict that the pregnancy will continue with 95.78% probability, with 67% sensitivity and 89% specificity. For the P threshold, the pregnancy will continue with 97.85% probability, with 80% sensitivity and 80% specificity. Conclusion: MGSD–CRL and P could predict patients with low abortion risk. However, at the 10th week of pregnancy, FHR  175 beats/min should be evaluated for this purpose by future studies with larger sample sizes. Key words: abortion, crown–rump length, fetal heart rate, gestational sac, progesterone. Introduction The first trimester is usually accepted as the most important developmental period of the pregnancy. 1 During the last two decades, a lot of information has been gathered about the first trimester of preg- nancy thanks to developments in new real-time ultrasonographic equipment and in vitro fertilization programs. Although the true incidence of spontaneous abortion is unknown, approximately 15% of clinically evident pregnancies end in spontaneous abortion. 2 Many researchers have tried to find some useful ultrasono- graphic markers in early gestation in order to predict Received: September 23 2007. Accepted: June 2 2008. Reprint request to: Dr M. Metin Altay, 48. cadde Yonca Apt. No: 12/31, 06520 Cukurambar, Ankara, Turkey. Email: altay_metin@yahoo.com doi:10.1111/j.1447-0756.2008.00927.x J. Obstet. Gynaecol. Res. Vol. 35, No. 2: 287–292, April 2009 © 2008 The Authors 287 Journal compilation © 2008 Japan Society of Obstetrics and Gynecology