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.
Sexual positions
Deep penetration, for example doggy style, means the male sperm that can swim faster start their race closer to the cervix and are more likely to reach the egg first, resulting in a boy. To try and conceive a girl, Shettles suggested avoiding deep penetration, favouring the missionary position.
Almost everyone has around a 50% chance of having a boy and a 50% chance of having a girl. What we can say is that dad's sperm determines whether a baby will be born as a boy or a girl.
But researchers say factors later in pregnancy are more likely to explain the phenomenon. Scientists have found some unexpected clues that could help explain why 51 percent of the babies born in the United States are male.
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.
While historically, there have been about 105 boys born for every 100 girls worldwide — which creates a “sex ratio at birth” of 1.05 — the share of boy babies has increased in recent decades. 2011 data from the World Bank show the global sex ratio at birth is now 1.07, or 107 boys born for every 100 girls.
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.
There are also both personal and environmental factors that affect the average sex ratio. The chance of having a boy appears to decline with the mother's age, the father's age and the number of children the family already has.
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.
The egg and sperm each have one half of a set of chromosomes. The egg and sperm together give the baby the full set of chromosomes. So, half the baby's DNA comes from the mother and half comes from the father.
After all, children inherit half of their DNA from each parent: 50 percent from mom (through an egg), and 50 percent from dad (through sperm).
Best positions: deep penetrative sex is preferable. This helps to deposit the semen and sperm closest to the woman's cervix so they are given the best opportunity to get to the egg in the fallopian tube. Twelve hours before ovulation is thought to maximise the chances of conceiving with a boy.
Consider having a baby before your reach 30 or 35.
Therefore, if you're trying for a boy, it might be best to start early. The chances are highest for a woman to conceive a boy before age 30. It's age 35 for men.
My general response is that it's a 50/50 chance that a woman will have a boy or a girl. But that's not exactly true – there's actually a slight bias toward male births. The ratio of male to female births, called the sex ratio, is about 105 to 100, according to the World Health Organization (WHO).
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."
Who Determines the Sex of the Baby? Perhaps you've wondered which parent determines the gender of the child? It takes two to tango, but scientifically, it only takes the sperm to determine the baby's sex. The egg will always have an X chromosome, so it's up to the sperm to decide.
December 25 (Christmas Day) is the least common birthday, while January 1 (New Year's Day) is the second least common. December 24 (Christmas Eve) also makes the list as the 3rd least common birthday while July 4 (Independence Day) is the 4th least common birthday.
First, which month has the least birthdays? The data comes from the Centers for Disease Control and Prevention and the Social Security Administration. The rarest month to be born in is February, making Aquarius the rarest zodiac sign. February is the shortest month of the year, even with a leap year.
Gender predictions made by ultrasound have an accuracy rate "north of 90 percent," Carr said.
Fertility treatment
Some fertility drugs work by stimulating a woman's ovaries, which can sometimes cause them to release more than one egg. If sperm fertilizes both of these eggs, this can result in twins. In vitro fertilization (IVF) can also increase the chance of conceiving twins.
Male baby pregnancies are more likely to result in complications, possibly because they grow faster in the womb and require more nutrients and oxygen than supplied by the mother through the placenta -- the temporary organ that attaches to the wall of the uterus during pregnancy to help the fetus grow and develop.