Assisted reproductive technology (ART) may be associated with the increased proportion of multiple birth infants affected by congenital abnormalities since the 1980s, European research suggests.
The authors say that the findings should lead to changes in the counseling of woman with multiple pregnancies and the support in place for women after birth, and suggest that it could also influence embryo transfer policy.
The study used data from 14 European countries, and included 5.4 million births between 1984 and 2007.
The overall rate of multiple births increased from 1984-7 to 2004-7, rising from 2.32% to 3.09% of deliveries, with most of this rise being accounted for by dizygotic twin and multiple births. Over the same time period the prevalence of congenital anomalies from multiple births increased from 5.60 to 10.90 cases per 10,000 births.
The authors found that, while absolute rates of both chromosomal and nonchromosomal abnormalities in multiple births increased during the study period, the risk for chromosomal abnormalities decreased relative to singleton births and was 29% lower in multiple births at the end of the study.
Meanwhile, the risk for nonchromosomal abnormalities in multiple births increased over time such that it was 41% higher than for singleton births at the end of the study. The authors say further research will be needed to assess whether this association is limited to pregnancies following ART.
Helen Dolk (University of Ulster, Newtownabbey, UK) and colleagues say that greater recognition of the impact of congenital anomalies on parents and health services is needed, and more support should be put in place for families.
Writing in BJOG, the authors say that the increased risk for congenital anomalies among multiple births may be due to ART or the characteristics of patients undergoing ART, rather than being linked to multiple births themselves.
However, women are less likely to terminate multiple pregnancies following prenatal diagnosis of abnormality because of the usually unaffected sibling or siblings. This may have contributed to the higher rate of congenital anomalies and perinatal mortality observed in this group compared with singleton births, Dolk and colleagues say.
"A single-embryo-transfer policy may not reduce the number of babies with congenital anomalies in the population, but may affect pregnancy course and neonatal outcome and reduce the extra demands placed on services and on parents by co-occurrence of multiple birth and congenital anomaly," conclude the authors.
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