Relationship between stage of pregnancy and some fetal parameters in early pregnant mares

Abstract EN

The aim of the current study was to establish ultrasonic biometric threshold of different uterine contents in thoroughbred mares and characterize the ultrasound changes in the conceptual swelling during the first 75 days of pregnancy.

A sequence of ultrasonographic examinations was carried out on 54 pregnant thoroughbred mares at 15, 18, 21, 28, 35, 45, 60 and 75 days of pregnancy during which conceptual swellings and fetal parts were described and measured, respectively.

The obtained results revealed that embryo and amniotic vesicle (AV) were detectable by days 21 and 28 days of pregnancy, respectively.

Organization (differentiation of the fetus into a morphologically-similar individual) was observed by day 45, while ossification was obvious by Day 60.

Ultrasonographically, the form of the embryonic vesicle changed from round, oblong (36/54, 66.67%) or round (18/54, 33.33%), triangular to irregularly circumscribed on days 15, 18, 21 and 28 of pregnancy, respectively.

High correlations were found between different studied fetal parameters and gestational age, where the highest correlation was found with diameter of the conceptual swelling (CSD, the conceptus including fluid and membranes, r=0.99, P<0.01), amniotic vesicle diameter (AVD, r=0.99, P<0.01), uterine diameter (UTD, mean diameter of the uterus at the level of the conceptus, r= 0.99, P< 0.01) and the crown-rump length (CRL, r=0.96, P<0.01) during early pregnancy.

In conclusion, the overall data indicated the feasibility and value of ultrasonographic fetometry in thoroughbred mares for evaluation of the early embryonic/fetal development and estimation of gestational age during the first 75 days of pregnancy.