Obstetric Outcomes and Successful Reduction of Twin Pregnancies Achieved by In Vitro Fertilization

The use of in vitro fertilization methods around the world is constantly increasing. In some developed countries, up to 5% of newborns are as a result of pregnancies after IVF procedures. In vitro fertilization as one of the main and widespread methods for treatment of infertility is the main reason for the high frequency of multiple pregnancies, which, in many countries, is still too high. Most of the multiple pregnancies are in fact twin pregnancies. Twin pregnancies, regardless of how they are achieved, are associated with large number of complications compared with singleton ones. More often these pregnancies can lead to maternal complications and adverse pregnancy outcomes. Maternal complications include development of preeclampsia, gestational diabetes, placenta previa, placental abruption, premature rupture of membranes, antepartum and postpartum hemorrhage, and delivery by cesarean sections. Adverse pregnancy outcomes mostly include preterm birth (PTB), low birth weight (LBW), small for gestational age newborn (SGA), intrauterine growth restriction (IUGR), neonatal respiratory distress syndrome (RDS), and admission to neonatal intensive care unit (NICU). A number of studies have found differences in the course of twin pregnancies according to their mode of occurrence – spontaneous or after IVF. Some of them have found that twin pregnancies after IVF are associated with poorer obstetric and perinatal outcomes, others do not find such a difference, and there are even studies that find a better outcome in IVF twin pregnancies. Twin pregnancy is a common occurrence after IVF procedure, because multiple-embryo transfer is commonly regarded as an effective strategy to improve the likelihood of a successful pregnancy. Understanding the risks of these pregnancies should be a strong motive for the transfer of fewer embryos during IVF procedures. The most effective way to do this is to transfer a single-embryo into the uterus in cases, where this is justified and the chances of getting pregnant are high. An important element in achieving this goal is the use of methods for vitrification of embryos, which leads to a sufficiently high rate of clinical pregnancies after freezing of embryos obtained by IVF and their subsequent transfer after thawing in case of failure of fresh ET.