THE EXPECTANT MARE
With a little TLC, your mare should progress through her pregnancy without much worry. Proper nutrition, deworming, exercise, and vaccinations will help ensure a healthy pregnancy, and you can look forward to the birth of your foal with greater confidence. Here are a few facts and information to assist you with your mare’s pregnancy.
CONCEPTION AND THE FIRST TRIMESTER
1. During the first 30 days of her pregnancy – there is a 10-15% chance that the embryo will be resorbed. Causes of absorption include: stress, illness, uterine infection, hormonal abnormalities, the presence of twins, and other factors that may be undetermined.
2. At conception, the fertilized egg travels down the fallopian tubes and enters the uterus around day 6-7. The fertilized egg (zygote) travels around the uterus until day 16 where it begins to settle down to a designated area of the uterus. By 6-8 weeks, the embryo implants into the wall of the uterus where it will continue to grow for the remaining 9-10 months of the pregnancy. Pregnancy can be determined by ultrasound at 14-16 days of conception. We recommend that you ultrasound your mare again at 60-90 days to confirm survival of the fetus through the first trimester of pregnancy.
1. Ultrasound at 16 days pregnancy may reveal twins. Early detection of twins by ultrasound allows the choice of eliminating one of the twins. Mares reproductive tracts are not suited to carry twins to full term. Often, there are risks will your mare carrying twins:
-95% of the mares will resorb or abort twin pregnancies within 60 days of conception.
-If a twin pregnancy survives past 50 days, it is unlikely that two healthy foals will be born due to the limited space to grow and thrive in the mare’s uterus. Often, one or both foals will be born weak and very small.
-Twins surviving past 50 days may spontaneously abort at 6-8 months.
-Most twin pregnancies that survive until the last trimester will be born prematurely at 300-320 days with variable survivability.