BioNews reporting from ESHRE conference, Copenhagen: IVF babies born after single embryo transfer (SET) are healthier than those born after more than one embryo is transferred, say researchers, in two studies presented at the annual conference of the European Society of Human Reproduction and Embryology in Copenhagen this week.



In the first study, Dr Diane De Neubourg, from the Antwerp Centre for Reproductive Medicine, Belgium, looked at babies born following SET, to see whether they had 'similarly poor obstetric outcomes to those reported from singleton births at the time it was customary to transfer two or more embryos'. She reported some of the first findings of a follow-up study of SET outcomes. She said that babies born following SET in IVF or intracytoplasmic sperm injection (ICSI) are as healthy as single babies born following a natural conception. The clinic analysed data it already held, and also sent questionnaires to all its patients after birth or termination of pregnancy, asking about the pregnancy, delivery and the resulting children. The data were compared with that held on naturally conceived singleton children from the Flemish (Belgian) register of perinatal epidemiology.



The researchers found that factors such as birth weight, gestational age and the proportion of still births were very similar in both groups. The only significant difference found was between the incidence of hypertension reported during pregnancy: women who conceived naturally suffered hypertension only 4.6 per cent of the time, compared to 7.6 per cent in women who had undergone SET. 'We found very little difference between the SET babies and those conceived naturally', said Dr De Neubourg, adding that 'we believe that our work shows clearly that SET is best for mother and child', although she acknowledged that more data would have to be gathered over time.



The second study, reported by Dr Anja Pinborg, from the Rigshospitalet, University of Copenhagen, showed that singleton babies born after dual embryo transfer - therefore being a 'surviving twin' - resulted in major health risks. Her team collected data from 11 fertility clinics in Denmark from between 1995 and 2001 to establish the number of 'vanishing twin' IVF pregnancies that resulted in a singleton birth - this was found to be 10.4 per cent of all the singleton births following IVF.



The research team looked at the obstetric and longer-term health of these babies, in particular at whether gestational age - the week of pregnancy in which the child was born - might indicate a poorer outcome. 'We found a clear correlation between the incidence of neurological problems and the time of onset of spontaneous reduction' in the 'vanishing twin' babies, said Dr Pinborg. She added that 'the later in pregnancy that the twin was lost, the higher the risk of neurological problems in the survivor'. The team also found that the risk of the child dying within the follow-up period was 'higher for survivors of a vanishing twin than in those born from a single gestation'. In view of these findings, said Dr Pinborg, if a woman produced two or more high quality embryos, and was under the age of 37, SET should be recommended, although she added that the age criteria could be higher still, depending on the results of further studies.

Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.