The number of teenage girls getting pregnant in England and Wales is the lowest it has been since 1969.
The rate for girls under 18 becoming mothers was 22.9 conceptions per thousand 15- to 17-year-olds in 2014, the Office for National Statistics (ONS) revealed.
The number of teenage mothers fell to 22,653 in 2014, compared with 24,306 in 2013, a decrease of 6.8%. In 1969, when records started, there were 45,495 teenage pregnancies.
The rate of teen pregnancies has more than halved since 1998, when there were 47 conceptions per thousand teenagers.
Hadley called this finding an "extraordinary achievement".
"Despite the big reduction, the job is not done," she said, according to BBC.
"England continues to lag behind comparable western European countries, teenagers continues to be at greatest risk of unplanned pregnancy and outcomes for some young parents and their children remain disproportionately poor."
The official figures also showed the rate of conception among under 16s was down 10%, with an estimated 4,160 pregnancies in 2014 compared with 4,648 in 2013.
The ONS also revealed variations in pregnancy rates between different areas, ranging from 18.8 (per 1,000 women aged 15 to 17) in the South East and South West to 30.2 in the North East.
Sexual health charity FPA's CEO Natika H Halil said it is great there has been a continued decrease in the teenage pregnancy rate.
"Not all teenage pregnancies are unplanned or unwanted, but young people who become parents under 18 have a higher risk of poorer health, education, economic and social outcomes," she said.
"This ongoing reduction is the result of a joint effort, including the legacy of the Teenage Pregnancy Strategy, which ended in 2010, and the continued work of health and education professionals to support young people in making informed choices that are best for their lives."
However Halil said for the areas which have seen continued higher rates since 2013, it is important there is investment in and commitment to prevention services.
"In the last year we have seen the Government fail to make sex and relationships education statutory and significant cuts made to public health budgets in England," she added.
"Neither is going to help bring the country’s teenage pregnancy rate more in line with other countries in Europe and both need to be given serious consideration."
To read the full report on pregnancy rates and ages, visit ons.gov.uk.