External validation of a simple scoring system to predict pregnancy viability in women presenting to an early pregnancy assessment clinic.

Abstract

A scoring system combining clinical history and simple ultrasound parameters was developed to predict early pregnancy viability beyond the first trimester. The scoring system has not yet been externally validated. This study aimed to externally validate this scoring system to predict ongoing pregnancy viability beyond the first trimester. This prospective observational cohort study enrolled women with singleton intrauterine pregnancies before 12 weeks of gestation. Women underwent examination and ultrasound scan to assess gestational sac size, yolk sac size, and fetal pulsation status. A pregnancy-specific viability score was derived in accordance with the Bottomley score. Pregnancy outcomes at 13 to 16 weeks were documented. Receiver-operating characteristic curve analysis was used to assess the discriminatory performance of the scoring system. In total, 1508 women were enrolled; 1271 were eligible for analysis. After adjustment for covariates, miscarriage (13%) was significantly associated with age ≥35 years (odds ratio [OR]=1.99, 95% confidence interval [CI]: 1.19-3.34), higher bleeding score (OR=2.34, 95% CI: 1.25-4.38), gestational age (OR=1.17, 95% CI: 1.13-1.22), absence of yolk sac (OR=4.73, 95% CI: 2.11-10.62), absence of fetal heart pulsation (OR=3.57, 95% CI: 1.87-6.84), mean yolk sac size (OR=1.25, 95% CI: 1.06-1.47), and fetal size (OR=0.82, 95% CI: 0.77-0.88). The area under the receiver operating characteristic curve was 0.91 (95% CI: 0.89-0.93). Viability score of ≥1 corresponded to a >90% probability of viable pregnancy. The scoring system was easy to use. A score of ≥1 could be used to counsel women who have a high likelihood of viable pregnancy beyond the first trimester.