Timing is everything when it comes to getting pregnant. Now new research reveals it’s just as key when it comes to yet another aspect of childbearing. It turns out the length of time between pregnancies can directly affect a baby’s health and survival.

Experts now recommend women wait at least eighteen months between pregnancies… but no longer than five years. Researchers analyzed sixty-seven studies published between 1966 and 2006. They found the risk for preterm birth, low birth weight and small size for gestational age increased if the time between pregnancies was less than eighteen months. Compared with infants born to mothers who waited eighteen months to two years between pregnancies, infants born to women who conceived less than six months after giving birth had a forty percent increased risk for premature birth and a sixty-one percent increased risk for low birth weight. Long intervals between pregnancies can also increase these adverse outcomes.

Worldwide, nearly a third of annual deaths in children under one month old are directly due to premature birth. This includes about five-thousand deaths in the United States, where up to ten percent of women get pregnant within six months after childbirth.

Experts recommend increasing access to birth control for family planning. Exclusive breastfeeding can also provide some protection from pregnancy, plus it has benefits for baby. Doctors also say new moms should continue taking prenatal vitamins containing folic acid to reduce the risk of birth defects, should the stork return sooner than expected.