The most complete control for triplets
Triplets are considered to be the highest risk pregnancies, and Doppler here plays the role of the main tool that allows you to notice in time that one of the fetuses has begun to suffer. Indices are measured in the umbilical cord artery of each fetus, in the middle cerebral arteries and, if abnormal, in the ductus venosus; blood flow in the uterine arteries is assessed separately as an indicator of the total placental reserve.
Data for each fetus are recorded under its permanent designation and compared with previous studies. It is the dynamics, and not a one-time result, that determines the tactics: a gradual increase in resistance in the umbilical cord artery in one fetus with stable indicators in the rest is a typical picture of selective growth retardation, requiring more frequent monitoring and discussion of the timing of delivery.
The volumetric part is carried out at the end of the appointment. Considering that with triplets, visits to the doctor are numerous, and the study itself is lengthy, the combination of functional diagnostics and three-dimensional visualization in one appointment significantly saves the family’s time.
Chorionicity is the main issue in multiple pregnancy
The prognosis of a multiple pregnancy is determined not so much by the number of fetuses as by the number of placentas and membranes. Dichorionic twins, where each fetus has its own placenta, proceeds relatively well. Monochorionic, where there is one placenta for two, carries the risk of specific complications associated with vascular connections within the common placenta, and requires monitoring every two weeks.
Chorionicity is most reliably determined at 11–14 weeks by the shape of the septal attachment site: the λ-sign indicates dichorionic twins, the T-sign indicates monochorionic twins. After 16–18 weeks, these signs smooth out, and the accuracy of the determination drops sharply. That is why the first study in case of multiple pregnancy is especially important and cannot be postponed.
Specific complications
With monochorionic multiple pregnancy, feto-fetal transfusion syndrome is possible - uneven redistribution of blood between fetuses through anastomoses of the common placenta. One fetus receives excess volume and polyhydramnios, the second receives less and suffers from oligohydramnios and growth retardation. The condition develops quickly and requires timely intervention, so the main way to detect it is regular ultrasounds with measurement of water pockets in each fetus.
The second common problem is selective growth retardation, when one fetus is significantly behind the other. A difference in the calculated mass of more than 20–25 percent is considered significant. Anemia-polycythaemic sequence is also possible, which is detected by the difference in peak systolic velocity in the middle cerebral arteries of the fetuses.
Why does the study take longer?
In case of multiple pregnancy, not one study is performed, but several: a full protocol for each fetus plus a general assessment of the uterus, placenta, septum and cervix. The volume of measurements increases as a multiple of the number of fetuses, hence the longer duration of treatment and higher cost compared to a singleton pregnancy.
An additional complexity is created by the relative position of the fruits: they cover each other, and the doctor has to spend a long time looking for the right cut. Sometimes part of the protocol is postponed for a follow-up visit a few days later - this is common practice and not a sign of trouble.