The likelihood of a woman remaining childless at age 35 increases with each year spent in a temporary position, a new Australian study finds.
"This is an important topic to study because the majority of people living in Western countries want to have children as part of leading a fulfilling life," Vivienne Moore, the study's senior author, wrote in an email to Reuters Health.
"Most prospective parents also want their children to be healthy," she added. Moore is a professor in the discipline of public health and the Robinson Institute at the University of Adelaide in Australia.
Studies have previously linked childbearing by older women with an increased risk of pregnancy and birth complications and abnormalities among the infants, the researchers point out in the journal Human Reproduction.
Moore said her team's study cannot determine why temporary jobs are linked to being childless later in life.
"However, several highly respected researchers have proposed that, for the mainstream of the population, (having) children is highly dependent on feeling secure about one's financial future," she said.
From that perspective, Moore added, having a temporary job does not fulfil the financial need to start forming a family.
For their study, she and her colleagues interviewed 643 women who were born at a hospital in Adelaide between 1973 and 1975. The women were between 32 and 35 years old at the time of the interviews.
About 67 per cent of the women had delivered at least one child by the time of their interview.
Most of the women were also in stable jobs by the time they had their children or by their interview. About 11 per cent were in temporary jobs.
Overall, the researchers found that a year of working in a temporary job was linked to an 8 per cent reduced likelihood of having a child by age 35, compared to women who had no temporary jobs.
What's more, a woman's likelihood of giving birth decreased as her time in temporary jobs increased.
The likelihood of having a first child by age 35 was 23 per cent lower after three years of temporary work, and 35 per cent lower after five years.
Those associations held true even after the researchers took into account the women's socioeconomic backgrounds, the education level of the women and their partners and the birthplace of the women's parents.
"Delayed motherhood is commonly viewed as a choice women make," Moore said. "From a media analysis we undertook, these women are often depicted as 'selfish' for (pursuing) careers instead of family formation."
The new study, she added, shows a societal reason for the shift toward older age at childbirth. "This is not just a matter of individual choice," she said.
Dr. Loralei Thornburg cautioned the new study can't prove that having temporary jobs caused women to have children later. She also said women at older ages can still have healthy pregnancies and deliveries.
"It's still not a good bet that you're going to have a problem, but it's the age when other risks start to rise," Thornburg said. She is a high-risk pregnancy expert at the University of Rochester Medical Center in New York, but wasn't involved in the study.
Thornburg said women of any age should see their doctors for preconception counseling before attempting to get pregnant.
Those visits help make sure women are making the best decisions, she said.
"Especially for women over 35, 40 or 45 (years old) who may have other medical or family concerns … Those are the women that I strongly encourage to come in and have that conversation before pregnancy," she said.