Luteinizing Hormone Surge More Accurately Correlates With Ultrasound Dating Of Early Pregnancy Compared To The Last Menstrual Period

Objectives 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). Methods 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 (GA(LH)), LMP (GA(LMP)), and first crown-rump length (CRL) that measured 5 mm or greater (GA(CRL)). 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 GA(LH)and GA(LMP)were compared to determine which measure showed greater concordance with the CRL. The mean absolute difference in days between the GA(CRL)versus GA(LH)and GA(CRL)versus GA(LMP)was determined. Results 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 GA(LH)showed a stronger correlation with the CRL (0.77) than the GA(LMP)(0.63;P= .002). The GA(LH)was more similar to the GA(CRL)than the GA(LMP), with a mean absolute difference of 2.0 versus 3.1 days (P < .0001). Conclusions When known, the LH surge appears to be more accurate than the LMP and should be used preferentially for dating of early pregnancy.