First trimester volumetric measurements: relation with hormone levels and fetal heart rate.

Purpose: This study aimed to examine two-dimensional ultrasound (2D US) volumetric measurements of 1st trimester structures and their relationship with β-hCG, progesterone, and fetal heart rate (FHR) in 6-10 weeks healthy pregnant women.

Methods: Using conventional 2D transvaginal ultrasound imaging, the crown rump length (CRL), yolk sac (YS) and gestational sac (GS) were measured in 80 women. Volumetric measurements were done in 32 cases that were selected among 80 women, using a simplified formula for the volume of a prolate ellipsoid: V = 0.523 × length × height × width. The β-hCG and progesterone levels were recorded. The heart rate was determined from M-mode tracings using electronic calipers.

Results: Moderately positive correlation was found between FHR versus CRL, embryo volume and GS volume. FHR increased linearly with CRL value, till CRL became 15 mm, after which it formed a plateau. β-hCG increased linearly till CRL was 15 mm, and then it formed a plateau. Progesterone level was stable till CRL became 20 mm, embryo volume 2 cm(3), after which it increased linearly.

Conclusion: Various ranges of relations are observed between FHR, obstetric, and hormonal measurements. The relationship between these parameters might be used for determination of abnormal growth and adverse outcomes in early pregnancy.