Termination of twin gestation by blastocyst crush in the broodmare.

This study investigates the outcome of manually crushing one blastocyst in twin pregnancies in broodmares. The survival of the uncrushed twin relies mainly on the stage of pregnancy, with the twin more likely to survive if the intervention is carried out before day 31.

Methodology

• The researchers carried out manual crushing of one blastocyst within 181 bicornuate twin pregnancies between days 24 and 45.
• The procedure involves causing the rupture of fetal membranes, which, in turn, has an impact on the survival rate of the uncrushed blastocyst.
• The trial found that, beyond day 31, the survival rate of the uncrushed blastocyst drops significantly if crushing has been performed.

Results of Bicornuate Twin Pregnancies

• The uncrushed twin could either survive, developing normally to full term, or stand rejected and resorbed akin to its crushed twin.
• There are instances where rupture is not achievable after day 35, regardless of the amount of pressure applied.
• Blastocysts crushed but not ruptured between days 35 and 45 could either resorb like their uncrushed counterparts (in 60% of cases), resorb without loss of the uncrushed twin (in 20% of cases), or survive, similar to the uncrushed twin (in 20% of cases).

Conditions for the Uncrushed Twin’s Resorption

• It is not possible for the uncrushed embryo to be resorbed unless the crushed twin is destroyed at any stage of the pregnancy.
• The rejection and resorption of the uncrushed twin is not due to the pressure transfer but is likely caused by physiological processes involving the hormone prostaglandin.

Use of Mefenamic Acid

• The study found that Mefenamic acid seems to enhance survival rates, particularly when crushing is effected after 31 days.
• However, a successfully crushed twin beyond this point may be lost between days 50 and 70.