Women who have short gaps between pregnancies are at increased risk of premature birth, research shows.
A US study of more than 450,000 births found that women with less than a year between their pregnancies were more than twice as likely to give birth prematurely as women who left at least 18 months after having their last child before conceiving again.
The latest study, published in BJOG: An International Journal of Obstetrics and Gynaecology, found that intervals of less than 18 months between pregnancies were more likely to lead to shorter subsequent pregnancies.
Emily DeFranco, assistant professor at the University of Cincinnati College of Medicine in Ohio, said: “Short inter-pregnancy interval is a known risk factor for pre-term birth; however, this new research shows that inadequate birth spacing is associated with shorter overall pregnancy duration.
“This study has potential clinical impact on reducing the overall rate of pre-term birth across the world through counselling women on the importance of adequate birth spacing, especially focusing on women know to be at inherently high risk for pre-term birth.”
The study, using birth records from the Ohio Department of Health, looked at the influence of “birth spacing” on the duration of following pregnancies.
Short interpregnancy interval (IPI) was defined as the time from the immediate preceding birth to subsequent conception of another baby.
Researchers categorised the women with short IPIs into two groups – IPI of less than 12 months and IPI of 12-18 months – and compared them with women who were considered to have an “optimal” IPI of 18 months or more.
The results showed mothers with shorter IPIs were more likely to give birth before 39 weeks compared with women with a gap of over 18 months.
Following an IPI of less than 12 months, 53.3 per cent of women had delivered before 39 weeks, compared with 37.5 per cent of women with an optimal IPI. The findings were even more stark for women giving birth before 37 weeks – the definition of a premature birth.
Women with an IPI of less than 12 months were more than twice as likely to give birth before 37 weeks compared with pregnancies following an optimal IPI – 20.1 per cent compared with 7.7 per cent.
John Thorp, BJOG deputy editor-in-chief, said: “We know that inadequate birth spacing is associated with more adverse pregnancy outcomes, including pre-term birth, in many countries like the US.
“This large population-based study further strengthens this and puts more emphasis on the importance of optimal birth spacing, especially among women with additional risk factors for pre-term birth.”
Louise Silverton, director for midwifery at the Royal College of Midwives, said: “This study supports advice that midwives give about birth spacing.
“If women are to breastfeed for the recommended six months before introducing solid foods, then they may delay ovulation and assist in birth spacing.
“Women need access to contraceptive advice to allow them to space their births.”