Serial investigations of early pregnancy in pony mares using real time ultrasound scanning.

The researchers observed the uteri of thirteen pony mares during the first two months of gestation using ultrasound. They tracked the progress of the conceptus, embryo, and fetus. They measured the diameter of the conceptus and length of the embryo and fetus daily.

Overview of the Study

• The research was conducted on thirteen pony mares, focusing primarily on the early stages of pregnancy, specifically the first two months.
• The main tool of investigation was real-time ultrasound scanning, which provided the researchers with daily images and progress updates on the gestation process.

First Identification and Observation

• The conceptus becomes visible via ultrasound scanning 12 to 16 days after ovulation. This is the earliest point at which the onset of pregnancy can be confirmed in the pony mares.
• The embryo was identified on the ventral surface, or the lower side of the conceptus starting from Day 21 of the gestation period.

Visualisation of Foetal Heart and Movement

• The study showed that it becomes possible to visualize the foetal heart after Day 22 of the gestation period.
• By Day 39, spontaneous movements from the foetus can be witnessed, which marks a crucial step in the development of the foal.

Foetal Membranes and Measurement

• The development of foetal membranes showed no consistent pattern in the study, making it a less predictable area of research.
• However, it was noted that the umbilical cord’s attachment site to the allantochorion (part of the placenta) was always in the dorsal aspect, referring to the upper side or back of the conceptus.
• To maintain a comprehensive record and monitor the growth rate, daily measurements of the diameter of the conceptus and the length of the embryo and foetus were taken throughout the study.