Embryonic loss in mares: Incidence and ultrasonic morphology.

This research paper studied embryonic loss in ponies and horses, using ultrasound to monitor pregnancies over 50 days. The study found that embryonic loss was higher among ponies during days 11 to 15 and was also more common after Day 20. The size of the lost embryonic vesicles and certain ultrasonic indicators can potentially signal an impending loss.

Study Methodology

• The researchers conducted an ultrasound of 154 ponies and 27 horses on Days 11, 15, 20, 25, 30, 35, 40, 45, and 50 to determine and monitor their pregnancies.
• The size of embryonic vesicles (the initial stage of the embryo that can be seen in an ultrasound image) was monitored and compared to control vesicles.
• The researchers also recorded ultrasonic indications of possible embryonic loss, including failure of fixation, presence of an echogenic ring or mass floating in a collection of fluid, absence of a heartbeat, and a decrease and disorganization in the volume of placental fluids.

Findings

• The embryonic loss rate amongst ponies was higher between Days 11 to 15 (18.2%) and this statistic was significantly higher than any subsequent five-day intervals (0% to 3.3% loss rate).
• Contrastingly, there were no losses recorded in horses during the Days 11 to 15 period. The loss rates for both ponies and horses between Days 15 to 50 were not significantly different.
• Embryonic vesicles that were lost between Days 11 to 15 were usually smaller than control vesicles. However, most vesicles grew at a normal rate.
• It was observed that a significant fraction of vesicles lost in the period of Days 15 to 20 and Days 20 to 25 were undersized during preceding examinations.
• In mares that experienced embryonic loss, the existence of undersized vesicles was found to be greater than in mares that maintained the embryo.

Implications

• A phenomenon called pseudopregnancy (a condition where the body shows signs of pregnancy despite the absence of an embryo) occurred more frequently after Day 20 following embryonic loss.
• Embryonic vesicles that got lost during days 11 to 15 usually wasn’t preceded by some visible indications on the ultrasound.
• Later stages of embryonic loss could be predicted through certain ultrasonic indications such as failure of fixation, presence of an echogenic ring or mass floating in a collection of fluid, an echogenic area in the dead embryo, absence of a heartbeat, and a decrease with disorganization in the volume of placetnal fluids.