twinsOver the last 30 years, the numbers of congenital anomalies have doubled in birth of multiples, according to a research study published in BJOG. The study was completed by researchers from the University of Ulster. Data was collected between 1984 and 2007, spanning nearly 25 years of birth records. Over that time data on more than 5.4 million births were recorded.

Based on information collected, researchers reported a multiples birth rate of 3%, accounting for 162,000 live births. Nearly 150,000 congenital anomalies were reported and 3.83% of those anomalies (more than 5,500) were found in multiples. When the data was broken into blocks based on the years of birth, a huge change in congenital anomalies was revealed. Between 1984 and 1987, about 5.9% of live multiple births suffered from a congenital anomaly. By the 2004 to 2007 period, that number had increased to 10.7% of live multiple births. Infants conceived as multiples were also more likely to suffer stillbirth and early neonatal death.

Congenital anomalies can affect one or both twins, which could increase the burden on parents and health care providers. According to Professor Helen Dolk from the University of Ulster, “The co-occurrence of multiple birth and congenital anomaly among live borns places particular demands on parents and health services. This may be even more relevant for the one in nine affected twin pairs where both babies have a congenital anomaly.”

The number of multiple births has increased over the last two decades. The increase in overall multiple births does not affect the risk of congenital anomaly, but it does affect the number of congenital anomalies reported. Assisted reproductive technology (ART) and advanced maternal age play a part in the increasing numbers of multiple births. Some fertility clinics are resorting to a single-embryo transfer policy in an attempt to reduce the number of multiple births associated with fertility treatments. 

Source: Boyle B, McConkey R, Garne E, Loane M, Addor M, Bakker M, Boyd P, Gatt M, Greenlees R, Haeusler M, Klungsoyr K, Latos-Bielenska A, Lelong N, McDonnell R, Metneki J, Mullaney C, Nelen V, O'Mahony M, Pierini A, Rankin J, Rissmann A, Tucker D, Wellesley D, Dolk H. Trends in the prevalence, risk and pregnancy outcome of multiple births with congenital anomaly: a registry-based study in 14 European countries 1984–2007. BJOG 2013; DOI: 10.1111/1471-0528.12046.