If you’re in your twenties or thirties and haven’t had children, a lot of unspoken questions about your childbearing decisions may have been hovering around the Thanksgiving table this past weekend. The next time potential grandparents in your family start wondering about your plans, it would be helpful to have some ammunition on what scientists say about the “best age” to have a baby.
Their answer depends, in part, on what you mean by “best.”
Their late teens or early twenties are biologically “best,” according to John Mirowski, a sociologist at the University of Texas at Austin. That’s when “the eggs are fresh and the reproductive system and other body are in the prime of their youth,” he wrote. Women in their twenties are less likely to have chronic health problems that put them or their babies at risk, and they have the lowest rates of miscarriage, ectopic pregnancy, stillbirth and infertility. But early pregnancy does not work well in today’s society, which is organized around small families and increasing full-time employment opportunities for women. If pregnancy occurs too early, social difficulties often follow. Mirovsky writes that at age 20 or younger, “pregnancy is more likely to occur out of wedlock, more likely to interfere with educational attainment, and more likely to crystallize a disadvantage.”
Even the early twenties seems in some circles to be too young to have a child – even when the mother is married and has a college degree. Michelle Horton, for example, gave birth to her son, Noah, when she was twenty-one, an age that seemed reasonable enough a generation ago. She created a blog called Early Mama, documenting her sense of isolation when she took Noah out and incredibly curious strangers asked her her age. She would usually say 25 or 27, just to keep them quiet. “But while I can lie to strangers, the fact remains that I am still a very young mother,” she wrote on her blog. “Most of my grad school friends, they cheat on their friends, get lost. I’ll have play dates in the future where other moms are 10, even 15 years older than me. But for me, for us, we’re ‘Get ready and we’re happy, even though your nose is upside down.'”
It is clear that a child’s biological “best age” does not match what would be a socially “best age”. Many twenties consider themselves too distracted and irresponsible for having a child. In the words of Mirovsky, “Humans mature reproductively about a decade before Americans mature socially.”
You could also define “best” to mean the best chance of a baby’s health, not the health of the pregnancy itself. With that definition, according to Mirofsky, one California study concluded that the “best age” for first birth, in terms of the lowest rates of birth defects, is 26. This is my age when my eldest daughter was born – and she was so perfect. A different study, based on national data, looked at a different measure of child health – overall infant mortality rates rather than birth defects – and identified a “best age” greater than it, which is 32.
Or you could define “best age” as the best outcome for the mother’s long-term health – making the ideal age even older. Using data from a telephone survey of women ages 45 to 95, Mirowsky found that those who reported feeling fit and active in middle age or old age, and with the fewest self-reported physical illnesses, delivered their first children, on average, in age 29. Those who reported the best overall health in middle age or in old age gave birth to their first children on average at 30; Those with the fewest aches and pains and the fewest chronic illnesses had them, on average, at 34 years old. Putting it all together, he said, the optimal age at first birth in terms of the mother’s long-term physical health is 31 years old.
And if you define the “best age” in terms of the longest life expectancy of the mother, the optimal age is the oldest of all. Mirovsky interviewed 1,890 mothers, inquiring about their current health, including chronic disease, movement problems, and self-assessments of malaise and other problems. He then looked at the mortality data, made some adjustments to educational attainment, and concluded that the “best age” for the first child, in terms of long-term health and maternal mortality, was 34. Social pressure to delay the onset of parenthood, he wrote, “is far outweighed by Big advantages of vital growth for young organs.” For young adults in their twenties thinking about how to time study, career advancement, and build a family, offer this advice: They can”
Mirovsky put it bluntly in a comment to a reporter for the Daily Mail: “A woman who gave birth to her first child at age 34 is likely, healthily, to be 14 years younger than a woman who gave birth at age 18.” The reporter then went on to draw the reader’s attention to the beautiful Sophia Loren, who gave birth to her first child at the age of 34. At the time the article was written (2005), Loren was 70 and still received “as much praise for her health” and beauty as she did whistle On-screen alert.
A different assessment of the long-term health of older mothers shows slight complexity, at least for women who want to have more than one child. While having your first child at age 34 may be fine, this other study suggests that it is even better to have another child before age 35.
That was the conclusion of Ohio sociologist Angelo Alonzo, who conducted a 2002 study that modeled Mirowsky’s use of a different data set, the Great National Health and Nutrition Examination Survey (N-HANES). After adjusting for social factors influencing health (race, age, income, health insurance coverage, smoking), compare the health status of two groups of middle-aged and late-life women: those who had any births after age 35, and those who had finished having children by then the time. So this was not seen at the age of first birth; Age 35 was considered as the maximum age for the last birth. Alonzo found that women who gave birth to children after age 35 had higher systolic blood pressure, higher blood glucose, poorer health as assessed by a physician, and impaired mobility later in life than women who gave birth to all of their children before age 35.
This is not exactly inconsistent with Mirovsky’s findings. It just means that two different studies came to two slightly different conclusions, and it would be hard to stick to them. For her long-term health, this collective wisdom says, a woman should get pregnant for the first time at age 34 — and her last pregnancy before age 35.