A government scheme to tackle teenage pregnancy has proven to be a major success.
Rates of teenage pregnancy in some parts of England fell by almost half after the Teenage Pregnancy Strategy (TPS) was introduced in 1999 by the then Labour government, a study has found.
The greatest impact was seen in areas of high deprivation and those locations that receive the most TPS funding.
Lead researcher Professor Kaye Wellings, from the London School of Hygiene & Tropical Medicine, said: "England's under-18 conception rate has fallen to its lowest level since the 1970s.
"What's more, progress has been made towards halting the cycle of inequality that has long been associated with teenage pregnancy."
The strategy included providing high-quality sex and relationships education, youth-friendly contraceptive services, support for young parents, and co-ordinated action, at national and local level.
Grants to help implement the TPS were allocated according to teenage pregnancy rates in different regions.
Scientists analysed data from 148 local authority areas to compare rates before and after the new strategy was brought in.
They also looked at information provided by the National Surveys of Sexual Attitudes and Lifestyles (Natsal).
The findings, published in The Lancet medical journal, show that after peaking in 1998 the under-18 conception rate declined at a moderate pace until 2006, when it began to fall more sharply.
Between 1998 and 2013, it dropped from around 65 conceptions per 1,000 girls aged 15 to 17 to 34 in areas receiving the highest TPS funding.
This compared with a fall from 36 to 20 in places receiving the lowest funding.
A decline in teenage pregnancy rates has also been seen in other countries though evidence suggests it has been less marked.
Professor Adam Balen, from the Royal College of Obstetricians and Gynaecologists (RCOG), said sex education was likely to have been an important factor behind the trend.
He said: "We welcome this positive news that the rates of teenage pregnancy have halved since 1999, particularly in areas with the highest deprivation. It is particularly promising that the sustained efforts on access to education and reliable contraception have been key to this achievement.
"Sex and relationships education (SRE) plays a vital role in providing young people with skills and information to negotiate relationships, protect their sexual health and prevent unplanned pregnancy."