Can Twin-to-Twin Transfusion Syndrome Be Explained, and How Is it Treated?
What Are the Differences Between Monozygotic and Dizygotic Twins? Monozygouc twins (MZ) carry higher fetal and neonatal risks than dizygotic (DZ) twins. The risks are particularly evident when MZ twins are connected to a single i.e., monochorionic (MC), placenta. Interfetal vascular anastomoses (chorangiopagus) are present between the individual circulations. In contrast, all DZ twins and one third of MZ twins have dichorionic (DC) placentas, which may be separate or fused, but rarely, if ever, contain vascular connections. The MC placenta is a single (i.e., not fused) structure teleologically programmed to service the needs of a singleton embryo/fetus. It is not always capable of adapting to the circulatory demands of MC twins (or for that matter, triplets or quadruplets). Regardless of which therapy ultimately is used, it seems clear that better outcomes in MC pregnancies can be obtained only if TTS is actively anticipated, sought for, and diagnosed at the earliest stage of gestation
