Does A Father’s Age Affect Down Syndrome?

When it comes to biological clocks, people often look squarely at women. Women have a “biological fertility window” which primes for optimal reproductive capacity between the ages of 18 and 31 years of age. The female reproductive system not only makes sex cells (gametes) called eggs, but hosts fertilisation (is where the female egg and male sperm meet and fuse together in sexual reproduction) and conception (the eggs and sperm developing into a zygote, or big ball of cells, embryo and then baby).

Before 18, the female womb is most often not quite mature enough to sustain a valid pregnancy, and the female herself has not reached her full growth mentally and physically until 18. After 31, the number of eggs begins to fall from 300,000 eggs approximately at 31 to less than 5,000 by age 40. As her egg number falls, the quality of the genetic information in her eggs falls with it, resulting in more genetic mutations due to less genetic repair as you age, and therefore, increased chance of genetic disorders in children born to elder mothers, such as Down’s syndrome.

What Is Down's Syndrome?

Down’s syndrome (also known as Trisomy 21) is where an extra chromosome is present at chromosome 21 in the genetic information of a cell called the DNA. Instead of a pair of two chromatids in a chromosome, the genetic information fails to divide properly when it goes through DNA replication and copies itself to make a new cell, and so you get three chromatids, hence the condition is called Tri (meaning three)- somy, at position 21 (Trisomy 21).

This condition can cause many genetic abnormalities in an offspring. For instance, dwarfism, reduced cognitive capacity, learning difficulties alongside physical changes such as a flat head and short neck. Other conditions which may occur are diabetes, gastrointestinal problems and many more problems. Consequently, such conditions may vastly impair a child’s quality of life, health and life expectancy.

Does Down’s Syndrome Come From the Mother or Father?

Down’s Syndrome is caused by a mutation in DNA, and therefore, can come from both a mutation in the mother’s DNA or father's DNA. Contrary to popular belief, a man also has a biological clock, with the optimum age for fertility between the age of 15 and 42. After this, the quality of male sperm diminishes, and the chance of genetic disorders, such as Down’s syndrome or Trisomy 21, also increases. The man is also likely to have a lower sperm count as he ages, and therefore, have less chance of conception in the first instance.

Recent metaanalysis (critical analysis of thousands of research trials) of studies undertaken over the last 20 years have concluded that male age is a big indicator for chance of Down’s syndrome. A man’s sperm contains half the genetic information that the baby will have, the other half comes from the mother.

Sperm is made in the testes under the direction of the hormones, Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Testosterone and Oestrogen. Sperm quality is impacted by the level of hormones, the temperature in the testes, the man's weight (with underweight and overweight men having low sperm count) and the number of mutagens (agents that mutate DNA such as UV sunlight on skin cells) that he comes across.

Dietary folate (B9 vitamin which alters the formation of DNA and RNA genetic information in a cell and genetic repair) and Cobalamin (B12 hormone that works with folate) also impacts genetic information in a cell such as a sex cell, and therefore impacts fertility and the chance of genetic diseases and disorders, such as Down’s syndrome in a child. Older fatherhood has been found to also increase the chance of neurological disorders such as ADHD, Schizophrenia, Autism and other neurodiverse and mental health related conditions.

Can You Prevent Down’s Syndrome?

Down’s syndrome is often tested for in early prenatal screening tests. Parents can decide whether or not to continue the pregnancy to full term, understanding the implications it may have on their potential child’s quality of life. They will have to weigh up whether they wish to create a life which, whist still having huge capacity for a full and remarkable life, may face many hurdles and challenges both mentally and physically.

There are many ethical and emotional consequences to be considered and whatever the decision made, it must be made with the child’s interests as well as the parents best interest at heart. No child deserves to face unnecessary suffering, and yet there are also religious, cultural, personal, and medical considerations to consider.