Five thousand more babies with birth defects are born each year in England and Wales than previously thought, researchers say.

At least 14,500 babies were born in 2009 with defects including congenital heart disease, spina bifida and gastroschisis – where the intestines develop outside the abdomen.

This represents more than 2 per cent of births in that year, higher than previous estimates which put the incidence of birth defects at 1.3 per cent. The new figures are based on data from five regional birth-defect registers plus two registers specific to particular diseases. The previous figures were based on Office for National Statistics data.

The study's authors, from Queen Mary, University of London, say the five regional registers cover only 28 per cent of the population, and data for other parts of the country is missing. Large regional increases in birth defects could go unnoticed and their causes would not then be investigated, they warn.

The number of birth defects has been monitored since the thalidomide scandal in the 1960s.