The teenage pregnancy rate in Wales fell slightly in 2008
Merthyr Tydfil has the highest teenage pregnancy rate for 15-17-year-olds in Wales and England, figures show.
Data for 2008 showed a rate of 73.5 conceptions per 1,000 girls of that age in the south Wales valley area.
The average for Wales and England is 40.6. The second highest figure in Wales is another valleys district, Rhondda Cynon Taf, with 59.2.
The teenage pregnancy rate in Wales in 2008 for girls in the age group fell slightly compared to the previous year.
Office for National Statistics (ONS) figures showed there were 2,600 conceptions among girls aged 15-17 in Wales, the same as 2007, but a slight fall to 44.2 in the overall rate.
There were a total number of 85 conceptions among girls in that age group in Merthyr in 2008, an increase of just four on 2007, but the pregnancy rate increased from 68.6 conceptions per 1,000 to 73.5.
The lowest rate in Wales was found in Ceredigion with 27.1 conceptions per 1,000.
Proposals to tackle teenage pregnancies in Wales were unveiled last summer with plans for better sex education to be taught.
The assembly government also aimed to cut the rates of sexually transmitted infections and highlight the dangers of unprotected sex.
A 2007 Estyn report said only a minority of schools in Wales taught sex education to a high standard.
The ONS statistics showed there were an estimated 887,800 conceptions among women of all age groups in England and Wales in 2008, a decrease of 0.9% on the 2007 figure of 895,900.
Conception rates decreased in all age groups between 2007 and 2008, with the exception of women aged 40 and above, where conceptions remained at 12.6 per 1,000 women.
In England, ministers pledged to halve the country's under-18 pregnancy rate by this year.
Data for 2008 revealed a drop in the number falling pregnant although the rate of decline is not enough to put the government on course to hit the target.
Gill Frances, chair of the Teenage Pregnancy Independent Advisory Group, said she was pleased the figures were back on their downward trend after a slight rise in the 2007 data.
A spokeswoman for the assembly government said: "While we welcome this reduction in conception rates for women under 18 in Wales, we are working hard to further decrease these rates by ensuring all children and young people in Wales receive an age-appropriate sex and relationships education."