Data contained in the Tobacco and Health in Wales report, published by Public Health Wales Observatory and the Welsh government, indicate that around one in six (16 per cent) Welsh females who were expecting in 2010 smoked throughout their pregnancy.
The report notes that the rate has fallen significantly since 2005, when 22 per cent of Welsh women continued to smoke while pregnant.
However, it remains the highest rate of all the UK nations, throughout which the average percentage of mothers who smoked throughout pregnancy in 2010 was 12 per cent.
The figures also show that 50 per cent of mothers in Wales managed to give up smoking either before or during their pregnancy. This compares with 54 per cent for the UK as a whole.
Those who are most likely to give up smoking during pregnancy include older mothers and those in managerial and professional groups.
Helen Rogers, Wales’ director at the Royal College of Midwives, described the figures as alarming and called for ‘urgent’ action.
She said: ‘Smoking in pregnancy can have serious and long-term effects on the developing baby, and the effects on the smoker themselves are well documented and supported by a substantial body of evidence.’