Worldwide, there are 107 boy babies born for every 100 girl babies. This skewed ratio is partly due to sex-selective abortion and "gendercide," the killing of female infants, in countries such as China and India where males are more desired.
Research over hundreds of years has consistently found that boys naturally outnumber girls at birth. The speculation is that this is nature's way of countering the relatively high mortality rates of males, and creating more of a gender balance in the population.
The ratio of male to female births, called the sex ratio, is about 105 to 100, according to the World Health Organization (WHO). This means about 51% of deliveries result in a baby boy.
More boys out of necessity
“Because of the one X and one Y chromosome, boys are more susceptible to stress in utero and early infancy,” says Dr Behie. This means we have evolved to have more boys as sadly some may not survive infancy. Girls are more likely to stand up to the stresses in utero.
Biological sex in healthy humans is determined by the presence of the sex chromosomes in the genetic code: two X chromosomes (XX) makes a girl, whereas an X and a Y chromosome (XY) makes a boy. In this way, it is the presence or absence of the Y chromosome in a healthy human that differentiates boy from girl.
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).
This suggests the initial stress of the pandemic caused a disproportionate loss of male fetuses among pregnant people in their second trimester, which may have resulted in fewer male babies being born in June 2020, according to the team.
When we look at the statistics the chances of having a boy or a girl are almost the same and there's no medical evidence to suggest we can influence this. You may, however, have heard about the 'Shettles Method'. In the 1970s Dr Shettles found that female and male sperm had different characteristics.
We might expect that naturally an equal number of boys and girls are born, but this is not the case. There are biological reasons why more boys than girls are born each year: around 105 boys per 100 girls.
Refining the probability a little bit, there are about 105 boys born for every 100 girls, so about 51.2 percent of babies are boys. The probability, then, of 14-boy families among all 14-child families, is (. 51214), which is about 0.0085 percent.
Nature is designed to favour the conception of boys from September to November and girls from March to May because of an evolutionary mechanism aimed at keeping the overall sex ratio as near to 50:50 as possible, the scientists said.
Male births were much more likely to require the use of oxytocin, a hormone which stimulates contractions. "Of the women carrying male infants, 70 per cent of them had completely normal deliveries, compared to 76 per cent of females."
Girls physically mature faster than boys on a physical level as well due to the quicker process of puberty. Girls undergo puberty earlier than boys by about 1-2 years, and generally finish the stages of puberty quicker than males due to their differences in biology.
Among humans, women's life span is almost 8% on average longer than men's life span. But among wild mammals, females in 60% of the studied species have, on average, 18.6% longer lifespans.
Most researchers agree that women are more emotionally expressive, but not that they experience more emotions than men do. Some studies have shown that women are more likely to produce inauthentic smiles than men do, while others have shown the opposite.
The benefits of having two boys
The bond between two brothers is stronger than most, so it can be incredibly rewarding having two sons. Not only will they give you hours of laughter as they play together; they can also look out for one another later in life.
Among 132 families that had three children of the same sex, 69 went on to have another child of that sex, and 63 went on to have a child of the opposite sex. The chance of having a girl after two boys was about 48 per cent and the chances of having a boy after two girls was slightly lower, at only 46 per cent.
In a survey of more than 500 parents by financial resource site MoneyTips released exclusively to MarketWatch, parents say it's the girls that cost you more. They estimate it costs, on average, an additional $2,160 a year to raise a daughter versus a son through age 18.
Speed: since sperm containing the Y chromosome are faster than those containing the X chromosome, if the egg is in the fallopian tube at the time of intercourse, there is a greater probability of a Y sperm reaching and fertilising it, which means there is a greater probability of the baby being a boy.
But the average age of women at first birth today (29.6) is not very different to what it was in 1938 (29.0), and fertility among women in their forties was higher at the start of WWII and during the 1940s than it was in 2010.
The report also showed that the average (or mean) age of mothers for all births rose from 24.6 years to 27.2 over the past three decades. Over one-half of all births still occur to women in their twenties–the peak childbearing years–but the average age in this group has shifted steadily upward since 1970.
Before the pandemic, births had been steadily declining for many years. There were almost 600,000 fewer annual births in 2019 relative to 2007—a 13% reduction.