The first time I got pregnant, I was a comparatively young mother, for my demographic: I was 25, in medical school, surrounded by classmates who, for the most part, were not reproducing yet. By the third pregnancy, 11 years later, I was over 35, which classified me, in the obstetric terminology I had learned in medical school, as an “elderly multigravida,” that is, someone who was having a child but not her first child, after 35. (If it was your first child, you were an “elderly primigravida,” or “elderly primip” for short — even as a medical student, I had a strong sense that no woman had invented this terminology.)

So by certain standards, I have experience as both a somewhat younger mother and a somewhat older mother, though not at the extremes in either direction.

National Vital Statistics Reports data released in January showed that in the United States, birthrates shifted in 2015: The birthrate for teenagers dropped to 22.3 births per 1,000 females ages 15 to 19 that year, a record low for the nation. And for women 30 through 44, the birthrates were the highest they have been since the baby boom era of the 1960s.

And as birthrates shift toward somewhat older mothers, researchers continue to look at what that says, both about who is getting pregnant when, and how that is associated with how their children do, especially when it comes to cognitive outcomes. (There’s also been some interesting research recently on paternal age, but these studies focused on the mothers.)

The trend all over the developed world in recent years has been more women having more children later; mean age in the United States at birth of a first child increased from 24.9 to 26.3 from 2000 to 2014. And whether it’s a first child or a later child, more women giving birth are 35 and older, which is still classified as “advanced maternal age” (well, it beats “elderly”).

In a study published in February in the International Journal of Epidemiology, researchers looked at evidence from three different large longitudinal studies in Britain, from 1958, 1970 and 2000-2, each involving around 10,000 children. They were looking at the association between maternal age at children’s birth and children’s cognitive ability when tested at age 10-11.

In the two earlier studies, there was a negative association; maternal age 35-39 at birth was associated with poorer cognitive scores in the children, tested a decade later; the children who had been born to mothers 25-29 did better. On the other hand, for the most recent study, that association was reversed; the children born to the 35- to 39-year-olds did significantly better on the cognitive testing than the children born to the younger mothers.

What had changed over time? The researchers found that they could explain this reversal by correcting for the social and economic characteristics of the mothers; different women, in different circumstances, were having their children later in life.

Alice Goisis, a research fellow at the London School of Economics and Political Science and the Max Planck Institute for Demographic Research in Germany, and the lead author on the study, said, “the characteristics of older mothers have changed drastically over time.” In the older studies, she said, the women who were having children into their late 30s were more likely to be women who had many children, and possibly poorer, whereas in the later study, the millennium cohort study done in 2000-2, the older mothers were more likely to be educated, and socioeconomically better off. Twenty-six percent were giving birth to their first child at ages 35-39, as opposed to 11 percent in the 1958 study.

“One question I am often asked is whether these results are suggesting that women should wait to have children so they will have smarter children, and the answer is that our results are not addressing that,” Dr. Goisis said. “These women tend to be advantaged,” she said, and to take better care of themselves during pregnancy; they were less likely to smoke and more likely to breast-feed, compared to the younger mothers.

“Nowadays children of older mothers have, on average, better outcomes because of the characteristics of women who tend to have children at older ages,” Dr. Goisis said.

Other researchers have looked at the question of how parenting attitudes and practices change as mothers grow older. In a study published online in December, researchers looked at how parenting practices and children’s development varied with maternal age in a group of 4,741 families in Denmark. Older mothers were less likely to be harsh with their 7- and 11-year-old children, either in terms of scolding or of physical discipline, they found, and their children were less likely to have behavioral, social and emotional problems.

“Older mothers seem to thrive better,” said Tea Trillingsgaard, an associate professor of psychology at Aarhus University in Denmark, who was the lead author on the study. “The mothers have more psychological flexibility, more cognitive flexibility, more ability to tolerate complex emotional stimuli from the children.”

Again, the researchers looked to see whether these differences were explained by another factor, by educational level or socioeconomic status, but even after controlling for all the demographic and socioeconomic factors they had, they still found that older maternal age itself continued to be associated with these more positive outcomes. “Emotional well-being tends to increase with age,” Dr. Trillingsgaard said. “Age in itself may be an advantage.”

We all know that fertility issues increase with older childbearing, with a large and complex fertility industry growing up in part to meet the needs of women who may have more difficulty conceiving later in life. But since having children is for most of us a huge and complicated decision, involving relationships, socioeconomic factors, geography, and the whole package of individual factors roughly summed up as life, love and the pursuit of happiness, decision making often doesn’t allow for simple planning where you target one age or another.

The clear message is that the children of women with more support and better health habits do better cognitively, so it’s important to support mothers of any age. What you learn as you grow up, intellectually and emotionally, may help you in the complicated job of taking care of your own children. And after all, growing up and helping people grow up is what this is all about.