Mothers should wait a year between giving birth and getting pregnant again, according to a new study

Chris Jackson/Getty ImagesThe Duchess of Cambridge with Prince George and Princess Charlotte.
  • Women have long been told to wait at least 18 months between giving birth and becoming pregnant again, but a new study suggested a year is long enough.
  • Having an interpregnancy interval of under 12 months, however, can lead to complications for both mother and baby.
  • Mothers older than 35 who become pregnant again after less than a year are more likely to put their own health at risk than younger women.
  • Researchers said they hope the findings will provide hope for older mothers worrying about their “biological clock.”

Women are often told that their fertility will drop off a cliff once they hit their mid-30s, meaning the notion of a “ticking biological clock” is well ingrained in the minds of many.

While the accuracy of this concept is often disputed, it’s not uncommon for couples to have children in close succession when the mother is over the age of 35 to ensure they have the best chances of conceiving and having a healthy pregnancy.

Current World Health Organisation guidelines recommend that mothers wait at least 18 months (and ideally 24) before getting pregnant again after giving birth, but an encouraging new study suggested waiting just a year may actually be enough.

According to the study of nearly 150,000 pregnancies, carried out in British Columbia, Canada, by the University of British Columbia and the Harvard T.H. Chan School of Public Health, 12 months is enough time to wait to ensure there is no great risk of premature birth, smaller babies, or infant and mother mortality.

The study confirmed, however, that becoming pregnant less than a year after giving birth would indeed put babies at risk of health problems.

For younger mothers, short interpregnancy intervals pose a greater risk to the baby – women between 20 and 34 years old who conceived six months after giving birth had an 8.5% risk of giving birth prematurely, while waiting 18 months decreased this risk to 3.7%.

Meanwhile, women over the age of 35 were found to be more likely than younger mothers to experience complications with their own health if their interpregnancy interval was less than a year.

Older women who waited just six months before conceiving again were found to have a 1.2% risk of maternal mortality or harm, while the risk decreased to 0.5% if they waited 18 months.

“Older mothers for the first time have excellent evidence to guide the spacing of their children,” senior study author Dr. Wendy Norman said, according to the BBC. “Achieving that optimal one-year interval should be doable for many women and is clearly worthwhile to reduce complication risks.”

The researchers said 12 to 18 months is the ideal gap.

“Older women need to weigh the risks to their own health and their infants’ health against the risks of not achieving the number of children they want,” Dr. Stephanie Teal, an OB-GYN at the University of Colorado School of Medicine, wrote in an article for the medical journal JAMA Internal Medicine.

“Simply telling older women to delay conception is not likely to improve health outcomes, as women are aware of their ‘biological clocks’ and many will value their desire for another child over their physician’s warnings,” she wrote.

Mandy Forrester, head of quality and standards at the Royal College of Midwives, said that, ultimately, when a woman becomes pregnant should be her choice, but the new research could help people make informed decisions.

“It will be a woman’s choice whatever age they are about how long they leave between their pregnancies,” she said in a statement.

“What is important is that they are aware of the evidence around birth spacing and that they make their choice armed with the right information. Health professionals will always support a woman in her choice, which will be about what is right for them and their pregnancy.”

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