The more complex the assisted reproduction procedure, the more likely the umbilical cord develops in an atypical place or have other abnormalities, a scientist told the 23rd annual conference of the European Society of Human Reproduction and Embryology (Wednesday 4 July). Mrs. Ilse Delbaere, from Ghent University Hospital, Ghent, Belgium, said that the study, including over 4000 twin pregnancies, was the first to examine umbilical cord abnormalities in such a large population.
For many years, scientists have known that both singletons and twins conceived after fertility treatment do worse in terms of duration of pregnancy and in live birth weight. "Certain umbilical cord pathologies, such as the insertion of the cord on the placental membranes instead of centrally in the placenta, or the absence of one artery in the cord, are known to correlate with an adverse outcome", said Mrs Delbaere, "and we wanted to find out whether these cord anomalies were more frequent after assisted reproduction."
The team studied data from the East Flanders Prospective Twin Survey (EFPTS), containing information on all multiple births in the region since 1964. "Since assisted reproduction was rather rare until the mid-eighties", said Mrs. Delbaere, "we analysed twins born between 1985 and 2004." The scientists compared cord characteristics from 2119 spontaneously conceived dizygotic (non-identical) twins and 2243 dizygotic twins who had been born as a result of assisted reproduction technologies (ART). Sub analyses looked at the different types of ART according to its 'invasiveness' and complexity.
The results showed not only that cord abnormalities occurred more frequently in ART twins, but that they varied according to the technique used.
"We found an incidence of velamentous insertion, where the cord attaches to the placental membrane, of 3.6% in spontaneously conceived twins," said Mrs. Delbaere. "But in twins conceived after IVF we found an incidence of 7.4%, and after intracytoplasmatic sperm injection (ICSI), where a single sperm is injected into an egg, it was 10.4%."
The scientists think that embryo implantation may be different after assisted reproduction. When an embryo is transferred to an area with poorer nourishment conditions, the placenta may migrate to more favourable areas, turning an initial central insertion of the cord into something more peripheral.
"We intend to follow up this work by studying whether the birth weight of twins born after ART is still lower when we exclude twins with umbilical cord pathology", said Mrs Delbaere. "We believe that this will be the first time that these two issues have been teased out in this way. We hope that our work will contribute to the understanding of how the placenta and cord develop early in pregnancy."
Materials provided by European Society for Human Reproduction and Embryology. Note: Content may be edited for style and length.
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