Prognostic significance of morphologic changes of the corpus luteum by transvaginal ultrasound in early pregnancy monitoring

Abstract

To determine whether the ultrasound appearance, size, or change in size of the corpus luteum of early pregnancy correlated with serum progesterone, estradiol (E2), or 17-hydroxyprogesterone or were predictive of pregnancy outcome. Transvaginal ultrasound assessment of the corpus luteum was performed prospectively on 55 women between 4-8 weeks' gestation. Forty-five (82%) subjects conceived in spontaneous cycles and ten (18%) conceived in cycles stimulated with clomiphene citrate. Fifty-three of 55 (96.4%) women had a second ultrasound assessment 5-8 days later (mean 6.7). Blood was drawn from each patient on the day of the ultrasound examination to measure hormone concentration. The appearance of the corpus luteum (macrocystic [more than 50% cystic], microcystic [less than 50% cystic], or noncystic) was not predictive of hormone concentration or pregnancy outcome. A nonviable pregnancy occurred in five of six (83%) women in whom a corpus luteum was undetectable by ultrasound and in 15 of 49 (31%) women in whom a corpus luteum was present (P = .01). There was no specific corpus luteum volume which could predict pregnancy failure. However, when a decreasing volume from first to second ultrasound examination was observed, 11 of 20 (55%) pregnancies resulted in nonviable outcomes compared to five of 27 (19%) when an increasing volume was observed (P < .01). There was no significant positive correlation between corpus luteum volume and plasma progesterone or 17-hydroxyprogesterone. A weak correlation was observed between corpus luteum volume and E2 (r = 0.38, P = .04). Our data reveal a lack of correlation between the size of the corpus luteum on ultrasound examination and known steroid products in pregnancies conceived during spontaneous cycles. Corpus luteum volume and steroid products were higher in those patients whose ovulation was induced with clomiphene citrate. Also, different morphologic appearances of the corpus luteum in early human pregnancy, based on the amount of cystic component, have no functional significance. However, a decreasing corpus luteum volume before 8 weeks' gestation is associated with a higher probability of early pregnancy loss.