The study involved over 89,000 women having second births in Scotland in 1992-8. Women whose interval between pregnancies was less than six months were much more likely to have had complicated first births. They were also more likely to be less than 20 years old, to smoke, and to live in an area of high social and economic deprivation.
Even among women with an uncomplicated first birth, and after taking account of social and economic factors, a short interval between pregnancies was associated with an increased risk of premature birth and neonatal death.
The authors propose that women should be informed of a small but significantly higher risk of premature birth and death when they conceive shortly after a birth.
Contraceptive advice should be targeted towards women who are most likely to have a short interpregnancy interval, such as teenagers and women who have lost a newborn baby, they conclude.