Teenagers are more likely to give birth prematurely and have a smaller baby than women in their 20s, new research has suggested.
Early birth risk is more pronounced if 14- to 17-year-olds have a second child, the study found.
The research team, which monitored 50,000 women in north-west England over a two-year period, is calling for better sex education and contraception.
It monitored 3,636 mothers between 14 and 17 at the time of birth, 7,506 aged 18 or 19, and 45,211 who were between 20 and 29.
Those aged under 17 were found to be 21pc more likely to have a premature first baby, and 93pc more likely to have their second baby early.
Links were also found between younger mothers and having a baby with a low birth weight.
Rates of teenage pregnancy increased with increasing social deprivation, the study also found, with more than one third of the teenage mothers coming from the most socially deprived areas.
Researcher Dr Ali Khashan, from University College Cork, said the risk of premature birth in younger mothers could be due to "biological immaturity".
"It is also possible that the increased risk of poor pregnancy outcome in the second teenage pregnancy is related to numerous complicating factors such as greater social deprivation and less prenatal care."
Research team leader Professor Louise Kenny, a consultant at Cork University Maternity Hospital, said: "These results highlight the importance of ensuring pregnant teenagers have appropriate antenatal care.
"A vital component of this care is post-natal contraception to prevent a second teenage pregnancy with potentially higher risks of adverse outcomes.
"A first pregnancy may be the first and only time a pregnant teenager interacts with health services and this opportunity should not be overlooked."