The Truth About Male and Female Biological Clocks

Recently, Tricia Tongco posted a StumbleUpon page about female and male fertility. She stated that "Fertility declines in men much later than for women".
 
Not quite right.
 
This is what happens to male fertility with age:
  • A 2011 report published in the medical journal Reviews in Urology found that the percentage of sperm with highly damaged DNA was significantly higher in men aged 36 to 57 years than in those aged 20 to 35 years.

  • A 2015 report published in the medical journal Reproductive Biology and Endocrinology found that increasing paternal age increases the incidence of different types of disorders like autism, schizophrenia, bipolar disorders, and childhood leukemia in offspring.

  • A 2006 paper published in the Proceedings of the National Academy of Sciences reported a steady increase in sperm DNA fragmentation with increasing age of the study participants, along with increases in gene mutations. The co-author, Dr. Andrew Wyrobek stated "This study shows that men who wait until they’re older to have children are not only risking difficulties conceiving, they could also be increasing the risk of having children with genetic problems.”
 
  •  A 2008 study analyzed samples taken from more than 21,000 intrauterine inseminations. They found that sperm from men in their late 30s was less likely to result in healthy pregnancy than sperm from younger men. Men older than 40 were successful in fertility treatment only in 10% of cases, and one third of these cases resulted in miscarriages.
 
  • Another study examined the rates of successful pregnancies in 59 fertility clinics for almost 2,000 couples. They found that women younger than 30 years old are 25% less likely to conceive a baby if her male partner is 40 years or older. Women 35 to 37 years old are 50% less likely to conceive if their male partners are 40 years or older.

So male fertility declines dramatically in the third decade of life when you look at how likely a man is to get a woman pregnant and how likely he is to father a healthy child.

Now what about women?
  • According to the American Society for Reproductive Medicine, female fertility peaks between the ages of 23 and 31. After that, fertility declines by about 3% per year. The average 39-year-old woman has half the fertility of a 31-year-old woman.
 
  • According to the California Birth Defect Monitoring Program, incidence of miscarriage rises dramatically with maternal age, from 10% for women aged 20-24 to 25% for women aged 30-34, to 50% for women aged 40-44.
 
  • It also reports that incidence of birth defects among babies born to mothers 20-24 years of age is about 14 out of 1,000 live births and miscarriages. By age 35, this figure more than doubles to 29 out of every 1,000 live births and miscarriages.

From a biological viewpoint, the ideal time for men and women to reproduce is early-twenties to mid-thirties. The problem is that those years EXACTLY overlap with the years workers are expected to launch successful careers. If you try to launch your career at 30 rather than 25, you will be sidelined. And THAT is what Millennials need to address—how to change our expectations and definitions of what constitutes a successful career. 
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Dr. Denise D. Cummins is a cognitive scientist who specializes in decision-making and reasoning. In addition to publishing in peer reviewed scientific journals, her work also appears in popular venues such as PBS Newshour Making Sen$e, Scientific American, and Psychology Today. More information about her can be found on her homepage.

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