Determination of equine fetal sex by Doppler ultrasonography of the gonads.

Summary

# Determination of Equine Fetal Sex by Doppler Ultrasonography of the Gonads Early fetal sex determination in mares has traditionally relied on identifying the genital tubercle between 55 and 70 days of gestation, but this approach is frequently unreliable due to excessive allantoic fluid, vigorous fetal movement, and the considerable length of the umbilical cord obscuring anatomical landmarks. Resende and colleagues (2014) investigated whether Doppler ultrasonographic assessment of fetal gonadal tissue could provide a more dependable alternative, examining mares between 110 and 150 days of pregnancy. Their findings demonstrated that direct ultrasonographic evaluation of the developing gonads during this mid-gestational window yields reliable sex determination, offering equine practitioners and breeders a substantially more accurate method than earlier-stage assessment. For those routinely performing pregnancy monitoring—veterinarians, breeders conducting selection programmes, and managers planning foaling schedules—this technique extends the window for reliable sex identification and eliminates the frustration of inconclusive scans during the earlier, technically challenging period. Incorporating gonadal assessment into standard mid-pregnancy ultrasound protocols could become particularly valuable in breeding operations where early sex knowledge informs management decisions, nutritional planning, or selective breeding choices.

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Key Findings

• •Fetal sex identification by genital tubercle location is unreliable between 55-70 days due to allantoic fluid volume, fetal movements, and umbilical cord length
• •Ultrasonographic evaluation of fetal gonads at 110-150 days of pregnancy provides reliable sex determination

Conditions Studied

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