LYON, FRANCE – Compared with spontaneously conceived twins, twins who are conceived through assisted reproductive technology have an increased rate of umbilical cord abnormalities, according to the first large study to assess this. And the incidence of such abnormalities increases with the invasiveness of the fertility treatment, said lead investigator Ilse Delbaere, a Ph.D. student at University Hospital Ghent, Belgium.
“The umbilical cord characteristics that have been associated with adverse outcomes are seen more frequently after ART [assisted reproductive technology],” she said at the annual meeting of the European Society for Human Reproduction and Embryology. “Considering the effect of cord abnormalities in twin pregnancies after ART may further our understanding of the underlying mechanism responsible for adverse outcomes after ART,” she suggested.
The study compared umbilical cord characteristics in 2,119 spontaneously conceived dizygotic twins and 2,243 dizygotic twins who had been conceived with ART. The incidence of velamentous cord insertion–which has been associated with preterm delivery, low birth weight, fetal growth retardation, and malformations–was 3.6% in spontaneously conceived twins but was roughly doubled (7.4%) in twins conceived with in vitro fertilization (IVF) and tripled (10.4%) in twins conceived with intracytoplasmic sperm injection (ICSI), Ms. Delbaere said. Moreover, the incidence of single umbilical artery (SUA), was significantly higher in twins conceived through ovulation induction (1.9% vs. 0.6%). It was also higher in IVF and ICSI twins, but the difference did not reach significance, she said.
The findings support the trophotropism theory that placental migration is more common in twin pregnancies because of competition for nourishment. ART twin pregnancies are particularly vulnerable because 80% of ART embryos implant near the transfer location, “which is not always ideal,” she said. “The placenta may migrate to more favorable areas, turning an initial central insertion of the cord into something more peripheral.” She hopes to follow up her research by adjusting for cord abnormalities in ART twins to assess whether adverse outcomes are still more common in them than in spontaneously conceived twins.