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Baby boy or girl- What decides the sex of the baby

Maitri Woman

Team Maitri

Apr 12, 2022

So, what colour is the cake, Blue or pink?
What type of clothes did you decide to buy? Frilly skirts or cricket shorts?
All expectant moms go through moments of anticipation, uncertainty & nervous excitement wondering about the sex of the baby growing in the womb.

Have you ever wondered, what really decides the gender of your baby?
How does that little peanut-shaped foetus grow into a tiny baby boy or girl inside your uterus?
Well culturally in most societies, since ancient times, the woman has been held responsible for the sex of the baby.
However, this myth has long since been debunked.

So, who or what is it that really decides the sex of the baby? 
To put it plainly-  It is the male parent that determines the sex of the baby.
As you know, a baby inherits genes from both their parents. The genes are present in the DNA, which is located on the chromosomes. Chromosomes are located in the nucleus of the cell.
Every human being has 23 pairs of chromosomes, that is a total of 46 chromosomes, half of which are inherited from the father & the other half, from the mother. So, every individual gets 23 chromosomes from the father & 23 from the mother, thus inheriting a total of 23 pairs of chromosomes.

Chromosomes are of two types

Autosomes - Responsible for general body characteristics unrelated to sex characters.

Sex chromosomes- determine the sex & sexual characteristics of an individual.

A baby has 44 autosomes & 2 sex chromosomes ( 22 pairs of autosomes & 1 pair of sex chromosomes).

It is these sex chromosomes that play the deciding role in determining the sex of the baby. 

There are 2 types of sex chromosomes-  One is the X chromosome and the other is the Y chromosome.

Genetically speaking, females have two X chromosomes and the chromosomal structure is written as 46XX. Males have one X & one Y chromosome as the sex chromosomes and is written as 46XY.

Every baby gets 22 pairs of autosomes & one pair of sex chromosomes from the parents. So if the baby has received X chromosome from the mother & X chromosome from the father, the 23rd pair of chromosomes will be XX and the baby will develop into a girl baby. 

Whereas, if the baby gets X chromosome from the mother & Y chromosome from the father, the  23rd pair of chromosomes will be XY and the baby will develop into a baby boy.
Thus, the presence or absence of The Y chromosome determines the sex of the baby.

All eggs produced in the mother’s ovaries will have X chromosome only because females do not have any Y chromosome. Whereas, half of the sperms produced in the father’s testes will have X chromosome, while the other half will have Y chromosome on them.

So a baby's sex is determined at the time of conception. As you know, conception can only take place if the sperm fertilizes the egg.  The egg contains an X chromosome, and the sperm contains either an X or a Y chromosome. 

A baby who inherits the X chromosome from the father is a female. She now possesses two X chromosomes ( 46XX). 

Whereas, a baby who inherits the Y chromosome from the father is a male ( 46XY). He now possesses one X and one Y chromosome.

The Sex chromosomes then determine whether the growing baby will possess testes or ovaries & correspondingly will be a boy or a girl. Male and female sex organs develop from the same primordial germ cells. Primordial germ cells are basic primitive cells called the stem cells which have the ability to differentiate into oocytes(eggs) or spermatozoa (sperms).  The fate of primordial germ cells depends on the chromosomes and the presence or absence of male hormones. This determines whether the germ cells will ultimately develop into female organs or male organs.

How does the Y chromosome determine the sex of the baby?

In males, a region on the Y chromosome triggers the development of testicles, which in turn, produce male hormones. Male genitals develop in response to male hormones from the foetal testicles.

In a foetus who does not have a Y chromosome, and consequently who is without the effects of male hormones, the genitals develop as female by default.

Can a woman’s diet affect the sex of the baby?

For centuries, people have been trying to find out how they can manage to get a baby of their choice- boy or girl. 

Consequently, many methods have been tried & claimed to be a sure-shot formula for getting the desired gender of the baby. 

Many people claim that consuming a diet rich in magnesium & calcium can increase your chances of having a baby girl while a diet rich in potassium can help you conceive a boy. Similarly, there are beliefs that state that consuming almonds, figs, beans etc can help you conceive a girl while a diet rich in fresh fruits, vegetables, banana, avocados can increase your chances of having a boy. 

According to research published in 2008, there is a strong link between the consumption of a high-energy diet around the time of conception and giving birth to sons.

However, there is no conclusive evidence that gives recurrent fool-proof solutions regarding any of these beliefs and none of these can guarantee the gender selection for your baby. 

Can sex position influence the gender of your baby?

Scientifically speaking, No particular Sex position can influence the gender of your baby. It is the father’s chromosomes that determine the sex of the baby. 

At the most, the sex position can offer is a slight increase in the possibility of conception. 

This is because certain positions shorten the distance that sperm needs to travel to reach the egg. Ejaculating sperms as close as possible to the cervix increases your chances of pregnancy.

Superstitions regarding sex determination

Superstitions, Age-old folk tales, grandma’s nuskhas, there is no scarcity of myths going around, ready to entrap you in your quest to conceive the baby of your choice.

Eating meat and salty food for a baby boy to splurging on desserts for a darling daughter. Making love standing up for a son, to sticking to the missionary position for a daughter.

Some folk tales state that the lunar cycle affects the gender of your baby. That having sex on full moon days will result in a baby girl.

There are 700-year-old Chinese conception charts that tell women which dates will result in boy or girl conceptions, based on the mother's age and the month of conception.

Of course, there is no scientific evidence that any of this works.

Shettle’s method states that the sperm cells carrying the Y chromosome are smaller, lighter, faster and more fragile than the sperm cells carrying the X chromosomes, which are thought to be bigger, heavier and slower, but more resilient.

Many superstitions and folk tales can influence your mind but remember that none of these have any scientific basis.


The major factor that influences the gender of the baby is the sperm that fertilizes the egg.
If the sperm contains X chromosome, the baby will be a girl.
If it contains Y chromosome, the baby is a boy.
This process of which sperm will fertilize the egg & lead to pregnancy is a random process & as such, there is no scientific way to predict or influence the union of a particular type of sperm with the egg leading to the development of a baby boy or girl. 

Accordingly, it is unscientific & unreasonable to put the burden of giving birth to a boy or girl on the pregnant mom-to-be. The sex of the baby is determined by the father’s sperm & not the mother’s eggs, so it is the father who is responsible for the gender of the baby ( Though even He does not have any control over which sperm will fertilize the egg! ) 

Some IVF techniques have been developed to ensure the conception of a baby boy or girl but these methods have multiple moral, ethical & social implications and hence are not endorsed or recommended. 

As such, so far the gender of the baby is a matter determined by chance and all that we can control is to ensure that we give a healthy & safe pregnancy to the mom-to-be and a well-nurtured life full of love & support to the newborn baby. Rather than focussing on a boy or a girl baby, it is more important to develop a bond and nurture the baby with love. Read our article on Bonding with the baby to know more.

(Note: The concept of male or female sexuality is rapidly evolving in today’s society but for the purpose of this article, we adhere to the genetic & chromosomal constitution while we talk of boy or girl).

Fun Facts

Fun fact

The sperms that carry the X chromosome are believed to be more resilient & survive longer in the female genital tract. This is the basis for the belief that having sex 3-4 days prior to ovulation increases your chances of having a baby girl!

Maitri Woman

Team Maitri

Apr 12, 2022

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