- Spontaneous triplet pregnancy
- 1/7000 deliveries.
- Most result from assisted
reproductive technologies and are trizygotic and therefore trichorionic.
- The rate of monozygosity is
2-3 times higher in assisted pregnancies in comparison to spontaneous
conceptions.
- The importance of knowing the
chorionicity:
- To perform fetal
reduction at 8-12 weeks is becoming more frequent. There is a theoretical
risk of death or damage to the remaining fetuses due to placental
vascular anastomosis.
- Selective fetocide
during the second trimester for an anomaly of one fetus.
- Complication of
monochorionic placentation is more severe in triplet than in twin
pregnancy.
- Ipsilon zone. This junction
of the three interfetal membranes in triplet pregnancies displays a
characteristic Y-shaped or ipsilon zone. If the membranes are parallel to
each other and the ipsilon zone is not seen, then the intertwin membrane -
placental junction must be examined.
- Trichorionic: All three
membranes are of similar thickness and echogenicity.
- Dichorionic: One membrane is
thin and the other two are normal.
- Monochorionic: All membranes
are thin and hair like and may be difficult to identify.