Northwestern Prenatal Genetic Centre
Training Centre of Ott's Institute of Obstetrics & Gynecology RAMS
14-th Liniya Vasilyevskogo ostrova, 7
+7 (812) 677-14-08, 921-26-32, 921-26-37
Multiple pregnancy is considered to be highly risky when speaking of various complications for a mother and a
fetus, because for a woman's body it is more acceptable to carry one fetus. Therefore, the woman having multiple
pregnancy should have scans and observe the growth and development of the fetuses more frequently than the woman
carrying one fetus.
There are several types of twins - depending on the number of placentas and membranes.
Dichorionic diamniotic twins is the most favorable type of twins. Each fetus has its own placenta and amniotic space, separated from each other with amniotic septum. Fetuses can be of the same or different sex. The probability of retardation of one of the fetuses is 20% (4 times higher than in singleton pregnancy) the probability of preterm birth is 5% (1% in singleton pregnancy). In order to detect these complications in time, it is necessary to carry out ultrasound at 11-13 weeks, 18-22 weeks (as in singleton pregnancy) and then every 4 weeks prior to the birth (in singleton pregnancy only at 32-34 weeks). If any complications are identified the number of scans may be increased.
Monochorionic diamniotic twins occur when a fertilized egg splits into two parts. In this case the fetuses have a common placenta and separate amniotic space. Fetuses are always of the same sex and are genetically identical. Having a single placenta may lead to the development of specific complications associated with the fact that the vessels in the placenta can connect the circulatory system of both fetuses. In this case, one fetus gets a certain amount of blood from another fetus, and they both suffer from this. One has the excess blood, which leads to increased stress on its heart, and the second one does not receive enough blood, oxygen and nutrients, and begins to grow more slowly, resulting in intrauterine growth retardation. This complication is called twin-to-twin transfusion syndrome, and without timely treatment can lead to loss of one or both fetuses. In order not to miss this complication, it is necessary to do scan at 11-13 weeks (as in singleton pregnancy), and at 16, 18, 20, 22, 24, 26, 28 weeks of pregnancy. If the signs of twin-to-twin transfusion syndrome are detected, the scan should be carried out even more often - 1 time per week. If before 28 weeks of pregnancy no symptoms of this syndrome are detected, its further development is highly unlikely, and the scan can be performed once every 4 weeks like with dichorionic twins.
Monochorionic monoamniotic twins occur when a fertilized egg splits into two parts, with the fetuses having a common placenta and common amniotic space. Fetuses are always of the same sex and identical genetically. This is an extremely rare type of twins. It is usually accompanied by the greatest risk of complications, intrauterine growth retardation and fetal death. In addition to complications associated with a single placenta (see the description above), the fetuses are in the common amniotic space and not separated with an amniotic membrane. This can lead to twisting and compression of the umbilical cord, cessation of blood flow to one of the fetuses and, consequently, its death. The risk of this complication is very high, so the scan is carried out each week of pregnancy, and in case of the detection of signs of umbilical cord torsion hospitalization and daily observation of a fetus is recommended. If the state of one of the fetuses becomes critical, immediate delivery by cesarean section is required.
Maintaining multiple pregnancy requires highly skilled physician, and should be held in the center of an expert level.