Luteinizing Hormone Surge More Accurately Correlates With Ultrasound Dating of Early Pregnancy Compared to the Last Menstrual Period.

Abstract

To compare the use of the luteinizing hormone (LH) surge versus the last menstrual period (LMP) for the accuracy of pregnancy dating in fertile women with a diagnosis of recurrent early pregnancy loss (REPL). This was an observational cohort study using prospectively collected data at 2 academic REPL programs between 2005 and 2018. Women with a history of REPL and at least 1 subsequent live birth after the evaluation were included. All patients conceived by intercourse timed to the LH surge. Transvaginal ultrasound was examinations were performed 2 weeks after missed menses. The gestational age (GA) was calculated by the LH surge (GALH ), LMP (GALMP ), and first crown-rump length (CRL) that measured 5 mm or greater (GACRL ). A secondary analysis compared GA based on the first measurable CRL of less than 5 mm versus GA based on the first CRL of 5 mm or greater. The GALH and GALMP were compared to determine which measure showed greater concordance with the CRL. The mean absolute difference in days between the GACRL versus GALH and GACRL versus GALMP was determined. A total of 115 women with 118 subsequent pregnancies resulting in live birth were included, with a mean age at delivery of 35.5 years and a mean of 3.6 prior pregnancy losses. The GALH showed a stronger correlation with the CRL (0.77) than the GALMP (0.63; P=.002). The GALH was more similar to the GACRL than the GALMP , with a mean absolute difference of 2.0 versus 3.1 days (P < .0001). When known, the LH surge appears to be more accurate than the LMP and should be used preferentially for dating of early pregnancy.