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by Dr. Barry Ball From The Horse Report For more information about u.~ procedure, please contact the Equine Reproduction Service at the Veterinary Medical Teaching Hospital at (530) 752-0290. Ultrasound image of twin equine fetuses at Day 720. Arrows indicate the fetuses' chests. Managing twin pregnancy after Day 40 The advent of ultrasonography for early pregnancy detection in mares has dramatically improved the veterinarian's ability to reliably diagnose and manage twin pregnancy. Twin embryos that are detected by ultrasound between days 14 and 30 of pregnancy can often be managed successfully by manipulating the reproductive tract during an examination per rectum and manually terminating one of the embryos. The early and accurate detection of twin pregnancy with ultrasound is critical in the prevention of abortion late in gestation due to twins. As many as 80 percent of twin pregnancies present at 40 days of pregnancy will subsequently abort, and most of these abortions occur after the eighth month of pregnancy. Such abortion losses have tragic emotional and financial consequences for mare owners. In spite of careful and diligent management for detection of twins during early pregnancy, some cases of twin pregnancy escape detection until it is too late for early intervention. In particular, mares With a large number of uterine cysts may make early and accurate diagnosis of twin pregnancy difficult or impossible. In some of these cases, the accurate detection of twins may not be possible before 25 to 35 days of pregnancy and at that point, it may b e difficult to manually reduce the twin pregnancy. In some situations, when a twin pregnancy is detected after day 30 to 35 of pregnancy, it may be advisable to induce abortion with prostaglandin and then breed the mare again on a subsequent estrous cycle. To be successful, however, the timing of such an intervention is critical. Beyond day 35 to 40 of pregnancy, secretion of the hormone equine chorionic gonadotropin may block the mare's return to a fertile estms for two to three months. In the infrequent situation that twin pregnancy is not detected until after day 40 of pregnancy, the mare owner is faCed with a dilemma. The likelihood of an abortion later in pregnancy is high, and the fertility of mares that abort due to twin Pregnancy is often reduced during the subsequent breeding season. Because of the poor outcome of twin pregnancy in mares after day 40 of pregnancy, some mare owners choose to terminate the pregnancy by inducing abortion and then rebreed the mare at the beginning of the next breeding season. Because the consequences of twin abortion in mares are so severe, the Equine Reproduction Service at the UC Davis Veterinary Medical Teaching Hospital is developing a technique in an attempt to save some twin pregnancies that are detected after day 40 of pregnancy. This technique, a modification of a procedure originally described by Dr. N. W. Rantanen from Fallbrook, California, involves the selective destruction of one fetus to improve the survival chances for the remaining fetus. During this procedure, one fetus is humanely destroyed by directly injecting procaine penicillin into the fetus. The mare is carefully monitored with ultrasound after the procedure to confirm the humane destruction of one fetus in an effort to save the remaining fetus. If the procedure is successful, the deceased fetus becomes mummified within the uterus allowing the remaining fetus to continue to term. Unfortunately, at present, the success rate of the procedure (the number of live single foals produced at term) is only 30 to 35 percent. Nonetheless, the procedure may offer an alternative for mare owners faced with a twin pregnancy that is not identified until after day 40 of pregnancy. 106 JOURNAL OF EQUINE VETERINARY SCIENCE

Managing twin pregnancy after Day 40

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Page 1: Managing twin pregnancy after Day 40

by Dr. Barry Ball From The Horse Report

For more information about u.~ procedure, please contact the Equine Reproduction Service at the Veterinary Medical Teaching Hospital at (530) 752-0290.

Ultrasound image of twin equine fetuses at Day 720. Arrows indicate the fetuses' chests.

Managing twin pregnancy after Day 40

The advent of ultrasonography for early pregnancy detection in mares has dramatically improved the veterinarian's ability to reliably diagnose and manage twin pregnancy. Twin embryos that are detected by ultrasound between days 14 and 30 of pregnancy can often be managed successfully by manipulating the reproductive tract during an examination per rectum and manually terminating one of the embryos. The early and accurate detection of twin pregnancy with ultrasound is critical in the prevention of abortion late in gestation due to twins. As many as 80 percent of twin pregnancies present at 40 days of pregnancy will subsequently abort, and most of these abortions occur after the eighth month of pregnancy. Such abortion losses have tragic emotional and financial consequences for mare owners.

In spite of careful and diligent management for detection of twins during early pregnancy, some cases of twin pregnancy escape detection until it is too late for early intervention. In particular, mares With a large number of uterine cysts may make early and accurate diagnosis of twin pregnancy difficult or impossible. In some of these cases, the accurate detection of twins may not be possible before 25 to 35 days of pregnancy and at that point, it may b e difficult to manually reduce the twin pregnancy. In some situations, when a twin pregnancy is detected after day 30 to 35 of pregnancy, it may be advisable to induce abortion with prostaglandin and then breed the mare again on a subsequent estrous cycle. To be successful, however, the timing of such an intervention is critical. Beyond day 35 to 40 of pregnancy, secretion of the hormone equine chorionic gonadotropin may block the mare's return to a fertile estms for two to three months.

In the infrequent situation that twin pregnancy is not detected until after day 40 of pregnancy, the mare owner is faCed with a dilemma. The likelihood of an abortion later in pregnancy is high, and the fertility of mares that abort due to twin Pregnancy is often reduced during the subsequent breeding season. Because of the poor outcome of twin pregnancy in mares after day 40 of pregnancy, some mare owners choose to terminate the pregnancy by inducing abortion and then rebreed the mare at the beginning of the next breeding season.

Because the consequences of twin abortion in mares are so severe, the Equine Reproduction Service at the UC Davis Veterinary Medical Teaching Hospital is developing a technique in an attempt to save some twin pregnancies that are detected after day 40 of pregnancy. This technique, a modification of a procedure originally described by Dr. N. W. Rantanen from Fallbrook, California, involves the selective destruction of one fetus to improve the survival chances for the remaining fetus. During this procedure, one fetus is humanely destroyed by directly injecting procaine penicillin into the fetus. The mare is carefully monitored with ultrasound after the procedure to confirm the humane destruction of one fetus in an effort to save the remaining fetus. If the procedure is successful, the deceased fetus becomes mummified within the uterus allowing the remaining fetus to continue to term.

Unfortunately, at present, the success rate of the procedure (the number of live single foals produced at term) is only 30 to 35 percent. Nonetheless, the procedure may offer an alternative for mare owners faced with a twin pregnancy that is not identified until after day 40 of pregnancy.

106 JOURNAL OF EQUINE VETERINARY SCIENCE