Women who conceive less than 11 months after giving birth have a higher chance of going into labour or being medically induced before 37 weeks of gestation.
In addition, the odds of a premature birth are also increased for those who wait three years to have another baby, suggests a new study published in BJOG: an international journal of obstetrics and gynaecology.
The study used data from a million women in California who gave birth between 2007 and 2010, in order to assess whether interpregnancy interval was associated with preterm birth in women who had already given birth and those who had experienced a pregnancy loss (miscarriage, stillbirth or abortion). Of these women, 971,211 had already had a baby and 138,405 had suffered a pregnancy loss. Short interpregnancy interval was defined as conception after less than 18 months and long interpregnancy conception after more than 36 months. An interval of 18 to 23 months is considered the optimal interpregnancy interval, when the risk of preterm birth is 5.7% (1 in 17.1).
Results found that women who conceive less than six months after giving birth have a 70% higher risk of preterm birth than women with an optimal interpregnancy interval (absolute risk is 10% or 1 in 10), while the risk for those with an interpregnancy interval of six to 11 months is 20% higher (6.9% or 1 in 14.5). Women who wait 36 to 48 months, however, also face a 7% increased risk of going into labour or being induced early (6.3% or 1 in 15.9).
While those who conceive a child less than six months after a pregnancy loss, have a decreased chance of a preterm birth; the risk of this is 7.7% (1 in 12.9). In fact, researchers found these women, and women of advanced maternal age (over 35 years old) and couples with fertility problems, may benefit from a short interpregnancy interval.
Lead author, Dr Bat Zion Shachar from the March of Dimes Prematurity Research Centre at Stanford University in California, said: “Reducing the rate of premature births globally is a priority. This study adds to our understanding about the potential causes of preterm birth and highlights the importance of communicating the risks of inadequate birth spacing to women. We recommend that obstetricians and midwifes discuss child spacing plans with postpartum mothers, as well as encouraging the use of contraception to reduce the likelihood of unplanned pregnancy occurring soon after live births.
“Interpregnancy interval guidelines for women who have experienced a pregnancy loss are of special importance because these women often wish to conceive again with minimal delay. However, we did not observe an increased risk for preterm birth among women with a short interpregnancy interval after a pregnancy loss, and our results show that there doesn’t appear to be any advantage of waiting more than six months to conceive again after a pregnancy loss.”
