Study examines the best age for women to start having children

AUSTIN, Texas—The social and economic benefits of delaying parenthood more than compensate for reproductive health issues related to aging, according to new research by a sociologist at The University of Texas at Austin.

Dr. John Mirowsky, a sociology professor in the College of Liberal Arts, presented his findings at the American Sociological Association meeting in San Francisco.

The study examines the relationship of women’s health and mortality risk to parenthood and age at first birth. The sample was drawn from 2,215 women, 25 years or older from the 1986 U.S. survey of Americans’ Changing Lives, and its eight-year mortality follow-up.

“Many U.S. women going to college currently delay first birth to around age 30, which is about 12 to 14 years after the end of puberty,” Mirowsky said. “Obstetricians and gynecologists are worried about this long a delay, because women’s reproductive systems are at peak function a year or two after the end of adolescent growth.  Despite this, my literature review and data analyses find that delay of first birth until the late 20s or early 30s is associated with the best health outcomes for the infant and mother.”

The study shows a high level of current health problems among women who first gave birth in or shortly after puberty. Problems drop steadily the longer that first birth was delayed, up to about age 34, and then rise steeply again after about age 40. Comparison to non-mothers of similar age and race/ethnicity shows that the correlation of motherhood with health problems and mortality hazard switches from detrimental to beneficial with delay beyond about age 22.

“To our knowledge, this is the first study to map the hazard of death by age at first birth,” Mirowsky said.

Results show the highest mortality risks for mothers who had first births nearest puberty and the lowest mortality risks for mothers who had their first births in their 30s, while non-mothers are somewhere in the middle. Mothers whose first births occur at age 19 or later begin to gain advantage over non-mothers.

Results consistently support the bio-social view that women’s health benefits from delaying motherhood as long as possible. They consistently contradict the bio-developmental view that women’s health benefits form starting soon after puberty, when the body’s reproductive and other systems are at a youthful peak.

To date, most studies focus on short-run biological outcomes of the pregnancy such as spontaneous abortion, prematurity, low birth weight, complications of pregnancy or childbirth, and congenital anomalies, or on short-to-mid-run social outcomes for the mother such as low educational attainment, single parenthood, and poverty in early adulthood.

The study was funded by the National Institute on Aging and the National Institute of Mental Health.

For more information contact: Dr. John Mirowsky, 512-232-7064.