Echo-Biometry Assessment of a Quadruple Pregnancy in a Captive Capybara

A 5-year-old female capybara, conditioned ex situ before mating, was monitored by ultrasound to establish prenatal growth and assess fetal echo-biometric variables. The records were taken twice weekly until delivery (i.e., 5 months). The measurements included gestational sac width (GSW), gestational sac height (GSH), gestational sac length (GSL), crown-rump length (CRL), trunk diameter (TD), heart major axis (HMA), biparietal diameter (BDP), and femur length (FL). The gestational sacs were detected on the 25th day after mating (DAM), embryos appeared on the 42nd DAM, and the parturition of four healthy offspring occurred three days after reaching averages of 30.74 cm (CRL), 8.65 cm (TD), 5.37 cm (HMA), and 6.08 cm (BDP). For initial pregnancy and fetal growth, GSL and BDP seem to be the best measurements. The formulas shown here can be a reference for gestational age estimation. This longitudinal study shows that ultrasonography is helpful for early pregnancy diagnosis and gestational age determination in capybaras.