Between birth and re-pregnancy, a study suggests that there should be a break of at least one year. "Our study has identified an increased risk for both the mother and the baby when pregnancies are closely related," said lead author Laura Schummers of the University of British Columbia.

The findings were particularly important for older women, because they tended to pregnancies with short breaks. For the study published in the journal "Jama Internal Medicine", more than 148,000 pregnancies of more than 123,000 women in the Canadian province of British Columbia were evaluated.

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Of the women over the age of 35 who became pregnant less than six months after giving birth, 1.2 percent suffered serious complications or even died before, during or not long after birth. With a break of at least 18 months, the statistical risk dropped to about 0.5 percent. In women between the ages of 20 and 34, this increased risk was not present. For this, the risk of a premature birth at a very soon-to-be re-pregnancy was even more pronounced.

Schummers and her colleagues recommend in their study an "optimal interval between pregnancies" of about 18 months, with a margin of between 12 and 24 months. The World Health Organization (WHO) recommended in 2005 to wait even 24 months after pregnancy.

Short pregnancy break can be "rational decision"

In spite of the increased risk, a short pregnancy break may be a "rational decision", according to the researchers Stephanie Teal and Jeanelle Sheeder in a commentary on the study. The age of mothers has increased because of their career opportunities. "Clinicians should understand that women over the age of 35 may want more children than recommended or even give birth earlier." The risks had to be weighed.

The average age of women in Germany when giving birth to their children has risen to 31.2 years in the last few decades (2017). In 1991 it had been only 27.9 years.

Study leaves some questions unanswered

However, the study leaves questions unanswered: For example, the University of British Columbia did not investigate the reasons for the complications. Women who returned to their pregnancy after less than six months, according to the study, were most likely to come from low-income neighborhoods, were the least cared for, and most likely smoked during pregnancy.

Especially in young women, close successive pregnancies may indicate that they are unplanned, said co-author Sonia Hernandez-Diaz. "Whether the increased risks are due to our bodies being unable to recover in a timely pregnancy or factors related to unplanned pregnancies, such as inadequate prenatal care, does not change the recommendation," she said.

Access to contraception should be facilitated after birth. Women should avoid unprotected sex with men in the aftermath of childbirth.