A case of a twin surviving to term following the abortion of its co-twin at 9 months in an Arabian mare.

Overview

• This research article reports a rare case in which one twin foal in an Arabian mare survived to full term despite the other twin being aborted at 9 months of gestation.
• The surviving foal was confirmed by genetic analysis to be the co-twin of the aborted fetus, both sharing the same dam and sire.

Background

• Twin pregnancy in mares commonly leads to abortion, usually resulting in the loss of both fetuses because the mare’s uterus is not well-suited to support twins to term.
• Typically, if one twin is aborted or lost during pregnancy, the other twin does not survive either, making this case unusual and noteworthy.

Case Description

• The case involved a 7-year-old Egyptian Arabian mare carrying twin male fetuses.
• At 9 months of gestation, one fetus was aborted. This aborted fetus was smaller than expected for 9 months, roughly the size of an approximate 5-month-old fetus.
• The co-twin was still alive in utero at 9 months, and this foal later survived to full term.

Parentage Verification

• To confirm that both the aborted fetus and the surviving foal were offspring of the same mare and stallion, parentage analysis was conducted.
• Samples collected for analysis included:
• Skin tissue from the aborted fetus
• Hair samples from the dam (mare), sire (stallion), and the live foal
• The genetic testing confirmed both fetuses had the same parents, ruling out any mix-up or mismatch in pregnancy.

Author’s Interpretations and Hypotheses

• The authors discussed several possible explanations or scenarios that might explain the unusual survival of one twin to term after the other was aborted so late in gestation.
• While the exact mechanism wasn’t definitively determined, the case emphasizes that under some conditions, one twin may survive even if the other is lost, which contrasts with the typical outcome in equine twin pregnancies.

Significance of the Report

• This report is significant because it documents a rare and valuable case of a twin foal surviving to term despite late abortion of the co-twin, contributing new knowledge to equine reproductive science.
• Understanding such occurrences could help veterinarians better manage twin pregnancies and improve outcomes in horses.
• It also raises questions about fetal development dynamics and intrauterine interactions between twins in mares.