Older Mothers Have Taller, Thinner Kids

Kids born to over-35 mothers tend to be taller and thinner.

Kids born to over-35 mothers tend to be taller and thinner.

Newsweek (“Old Moms, Tall Kids“):

As reported in the journal PLOS ONE, investigators from New Zealand looked at 277 kids who were born after a normal, full-term pregnancy. When studied, the children were between 3 and 10 years old—not yet grown up but with a predictable growth trajectory. The researchers recorded their height and weight, took a few blood tests that may predict growth, and then sorted their findings according to whether the child was born when the mother was in her 20s or already had crossed the line into life as a 30-something.

By a significant margin, children born of older mothers were the clear winners: they were much taller and thinner than those whose mothers were younger. The difference wasn’t because the older parents were themselves taller and thinner; in fact, the researchers weren’t sure how to explain the findings, which are in line with observations made a few times in the past. Perhaps, they suggested, the hormonal mix produced during pregnancy by an older woman differs from that made by her younger counterpart.

This study comes along as more and more women have children later in life. As the report points out, in the last 30 years, “maternal age at first childbirth has increased by approximately 4 years in most developed countries,” meaning that in the richer part of the world, “most children currently are born to mothers aged over 30 years.”

The vagueness of the report intrigued me to look up the full PLOS ONE article, “Increasing Maternal Age Is Associated with Taller Stature and Reduced Abdominal Fat in Their Children,” which was surprisingly freely available.  The key findings:


Our cohort consisted of 126 girls and 151 boys, aged 7.4±2.2 years (range 3-10); maternal age at childbirth was 33.3±4.7 years (range 19-44). Children of mothers aged >35 and 30-35 years at childbirth were taller than children of mothers aged <30 years by 0.26 (p = 0.002) and 0.23 (p = 0.042) SDS, respectively. There was a reduction in childhood BMISDS with increasing maternal age at childbirth, and children of mothers aged >35 years at childbirth were 0.61 SDS slimmer than those of mothers <30 years (p = 0.049). Children of mothers aged 30-35 (p = 0.022) and >35 (p = 0.036) years at childbirth had abdominal adiposity reduced by 10% and 13%, respectively, compared to those in the <30 group. Children of mothers aged 30-35 years at childbirth displayed a 19% increase in IGF-I concentrations compared to offspring in <30 group (p = 0.042). Conversely, IGF-II concentrations were lower among the children born to mothers aged 30-35 (6.5%; p = 0.004) and >35 (8.1%; p = 0.005) compared to those of mothers aged <30 years. Girls of mothers aged 30-35 years at childbirth also displayed improved HOMA-IR insulin sensitivity (p = 0.010) compared to girls born to mothers aged <30 years.


Increasing maternal age at childbirth is associated with a more favourable phenotype (taller stature and reduced abdominal fat) in their children, as well as improved insulin sensitivity in girls.


Thus far, this is bearing out with my girls. I’m a little over 6’1″ and my late wife was just 5’5″, so I would expect kids of maybe slightly-above-average height. Our eldest, Katie, was born when Kim was 37 and I was 43; she’s in the 85th percentile in height but around the 50th percentile in weight. Our youngest, Ellie, was born a month shy of Kim’s 41st (and last) birthday and when I was 45; she’s in the 95th percentile in height and around the 60th percentile in weight.

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James Joyner
About James Joyner
James Joyner is Professor and Department Head of Security Studies at Marine Corps University's Command and Staff College. He's a former Army officer and Desert Storm veteran. Views expressed here are his own. Follow James on Twitter @DrJJoyner.


  1. Anon says:

    All PLOS papers are free. It seems to be the most highly-respected of the organizations publishing open journals.

  2. CSK says:

    Interesting. I was born when my mother was 27, and my sisters when she was, respectively, 31 and 36. I’m taller and thinner than both my sisters.

  3. Jeff Quinton says:

    Definitely our experience so far. My wife was 41 when our daughter was born and she has been consistently 95th-100th percentile for height and she is around 50th for weight.

  4. john personna says:

    This begs for an adoption study follow-up. Do older moms feed their children better?