Almost one in five girls say they have been pregnant at least once by the age of 18, according to a Government survey published today.

Just under half (46 per cent) decided to keep their baby, while more than a third (36 per cent), had an abortion, the figures show.

The statistics are part of wider research on the experiences of 18-year-olds in England, published by the Department for Education today.

The responses of thousands of 18-year-olds questioned for the Youth Cohort Study and the Longitudinal Study of Young People in England were analysed.

The findings show that of the 18-year-old girls questioned about pregnancy, 18 per cent had been pregnant at least once.

Of these, almost eight in 10 (79 per cent) had been expecting a baby on just one occasion, nearly one in five (18 per cent) had been pregnant twice, and 3 per cent had been pregnant at least three times.

The survey concluded there was a "noticeable trend" between the young women who fell pregnant by 18, and their GCSE results.

A third (33 per cent) of those who gained between one and four GCSEs at grades D-G had been pregnant at least once by the time they were 18, compared to just 6 per cent of those who scored eight or more GCSEs at Grades A*-C.

Teenage girls who were eligible for Free School Meals - a measure of poverty - at age 16, or who had parents who left school at 16, were also more likely to get pregnant by the age of 18, the figures showed.

According to figures published by the Office for National Statistics, there were 25.3 births for every 1,000 women under 20, in 2009.

Girls aged 15 to 19 accounted for 39,020 abortions carried out in England and Wales in 2009.

The figures show that 18 per cent of girls who said they were sexually active had been pregnant by the age of 18.