Chorioangioma is a placental tumor that is composed of an abnormal proliferation of vessels. These vessels may be connect to the baby via the umbilical cord. Although not uncommon (1% incidence), cases with chorioangiomas that measure greater than 4 cm in diameter are rare. Pregnancies with large chorioangiomas can be associated with pregnancy complications. These include hydrops fetalis (heart failure), growth restriction (poor growth of the baby), fetal/neonatal demise, and preterm birth. The cause of these pregnancy complications can be attributed to two factors. First, high-output cardiac failure may occur due to vascular steal from arteriovenous shunts in the tumor. Second, hemolytic anemia (low blood count) and severe thrombocytopenia (low platelet count), otherwise called Kasabach-Merritt Sequence, may develop.

Most pregnancies with a chorioangioma do not require treatment while the baby is in the womb. However, rarely, in cases of large chorioangiomas (defined as over 4 cm), the baby may be at risk. The following is a list of possible treatment options for pregnancies with large chorioangiomas and evidence of fetal compromise:

  1. Intrauterine transfusion. This may be necessary if there is ultrasound evidence of fetal anemia (low red blood cell count). Platelet transfusion may also be necessary.
  2. Amnioreduction. Amnioreduction is a procedure in which a needle is inserted into the amniotic cavity and the excess fluid is removed. The purpose of this procedure is to decompress the womb to prevent preterm delivery. This procedure may be necessary in cases with symptomatic polyhydramnios (excess amniotic fluid volume that is causing preterm contractions and/or a short cervix).
  3. Operative fetoscopy and laser ablation of chorioangioma feeding vessels. The procedure involves operative fetoscopy and laser occlusion of the feeding vessels to the tumor.

For further reading, please see the link below:

Los Angeles Fetal Surgery Publications