What are the odds of having children of the same gender?

Are large families of the same gender a statistical fluke? Mother of four sons, Gwen Loughman goes behind the myths
What are the odds of having children of the same gender?

In 1970’s Ireland, families with six or more children were the norm. CSO figures almost five decades later however, sees numbers for such families drop from 15,000 to a mere 3,000. Having four children in 21st century Ireland is considered a large family but to have more, and for those children to be all of the same gender, is a rarity and an attraction in itself.

Myths about how to conceive a girl or boy child have been around for centuries. During the reign of King Henry VIII it was widely believed the responsibility to produce the desired male gender fell to the female. Science has since proven otherwise.

Therese Murphy, lecturer in Medical Sciences, University of Exeter clears up just who determines the baby’s gender.

“A baby’s genetic sex is determined by the man’s sperm as the sperm cell will contain either an X or a Y chromosome. It is the Y chromosome that is essential for the development of the male reproductive organs. When a Y chromosome is not present an embryo will develop into a female.”

Sex ratio

Carmel Kennedy, Ballyphehane, Cork with her eight sons.
Carmel Kennedy, Ballyphehane, Cork with her eight sons.

Carmel Kennedy from Ballyphehane, Cork with eight sons aged 37 to 20 is no stranger to people passing comments about her brood over the years.

“I could talk for hours about some of the things people said. I did have girls but did not go to term with them. I always wanted a large family; I’m one of six girls and four boys and we had a beautiful childhood. Now I have eight healthy, respectful sons and lovely grand-daughters of my own,” she says.

Professor Louise Kenny from Cork University Maternity Hospital Perinatal Medicine says in general, worldwide, slightly more boys are born than girls. “If left to nature there will be about 105 boys born for every 100 girls. However, 2011 data from the World Bank show the global sex ratio at birth is now 107 boys born for every 100 girls, largely driven by the skewed ratio caused by sex selection prior to birth in China, where about 118 boys are born for every 100 girls.”

Statistical coincidence?

Michelle Masterson Power and husband David have four daughters aged eight to 14. Their sons are six and four. “Because we were used to being parents of just girls, it meant we didn’t know any differently. David grew up with five sisters and one brother so he was very comfortable being a father of daughters. But once the boys came along, we learned the truth in that old saying, boys wreck the house. That one is so true!

“ Michelle says her house was a very different one before the boys arrived. “It was very girly. Civilised, I’d say.”

Michelle Masterson Power and Cillian, Orlagh, Ciarán, Eimear, Aoife, Ailbhe, Masterson Power.
Michelle Masterson Power and Cillian, Orlagh, Ciarán, Eimear, Aoife, Ailbhe, Masterson Power.

Naturally, there was great excitement when Cillian arrived, creating a particular interest in nappy changes! “The girls each took turns holding him and I had to time them! They were amazed when he wee’d all over me one day.”

The odds of having a girl or a boy are the same with a one in two chance of it being one or the other. 50/50 if you like. However, what about bigger families of the same gender; are they a statistical coincidence?

Dr Murphy again: “The probability of having a boy or a girl from a genetics point of view, remain the same each time a baby is conceived. However, there is some epidemiological evidence to suggest other factors may influence sex determination in humans. There is an argument about the motility and/ or survival of Y-carrying sperm and X-carrying sperm and timing of ovulation but it’s important to note that there are no robust ‘biological’ explanations for their observations to date.”

There are various techniques and methods that allegedly improve the chances of conceiving a girl or a boy such as The Shettles Method and The Whelan Methods. Not forgetting particular diets and the slightly even more dubious practice of female douching. All have their believers and sceptics.

Professor Louise Kenny has this to say. “In a nutshell there is no evidence that timing of intercourse affects sex ratio. There are several scientific studies that have disproven this. Furthermore, there is evidence that limiting intercourse within the fertile time will reduce your chances of getting pregnant at all. So my advice to couples would be to accept that at every conception there is approximately a 50:50 chance of conceiving a child of either sex and there’s very little than can be done to materially alter this,” she says.

Historically speaking, there were massive gender divides. Concerns such as providing dowries for daughters and the birth of a male heir guaranteeing property retention saw one gender being preferred over the other. Thankfully, times have changed and when it comes to large families, issues like privacy and parental support are more relevant.

Gwen Loughman with her sons Liam, Conor, Brendan, and Iarla.
Gwen Loughman with her sons Liam, Conor, Brendan, and Iarla.

Carmel Kennedy had her own alternative support system in place when her boys were younger.

“My sisters and I were there for each other and my sons had lots of friends and were always out playing so we mums would all stand at our gates and keep an eye on the kids. My coffee mornings were a cup of tea at the gate! And at night we called to each other’s houses.”

She would agree being surrounded by menfolk meant privacy was limited. “I didn’t have any, I suppose. It’s only in the last seven years I have had my own bedroom space really as I always had a child or two asleep in my room. When they were babies and I was trying to shower, they used to scream at the door till I finished,” she says.

Konrad, 26, is Carmel’s sixth-born and says life with seven brothers was for him just normal but, “for an outsider looking in it must have looked mental. It was never a silent house. We were all into music so it was loud and with eight boys comes a tonne of friends so people were always in and out. My mother was very relaxed. I think she likes the noise. I think we all turned out fairly well. We know now it was tough for my mother. But she never let it show,” he says.

The teenage years are on the horizon for the Masterson Power family but Michelle is a woman of little or no fear. She feels can handle the mood swings and teenage dramas thanks to her daughters.

“The girls are great with their brothers. They are very much the bosses but are also quite tolerable as the boys are much more demanding physically. Their dad grew up with sisters and has a great understanding of girls particularly in the teenage years, I think the boys will be the same.” Michelle and David encourage their children to have the same values as their parents when they grow up. “I tell the girls to find a man like their dad.”

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