Fertilization: The determination of sex

The determination of the sex of the future baby will be established from fertilization. It is the sex chromosomes X or Y that determine the sex of the future baby. Since all eggs carry the X chromosome, it is the spermatozoon - X chromosome carrier or Y chromosome carrier - that determines the sex of the baby.

  • The mother (ovum) brings an X chromosome, and the father (spermatozoon) his X chromosome: it will be a girl (XX).
  • The mother brings an X chromosome, and the father his Y chromosome: it will be a boy (XY).

So there is statistically as many chances to have a girl as a boy.

The special case of twins

It is also during fertilization that twins (or more) will eventually be formed. This peculiarity can have two origins:

Dizygotic twins:

During ovulation, two eggs were emitted, and they are fertilized by two different spermatozoa. Two very distinct eggs are formed (hence the term dizygote). We are talking about "false twins", who can be of the same sex or not, and who will look like classic brothers and sisters.

Monozygous twins:

The egg has been fertilized by a spermatozoon, but the egg cell thus created splits in two, forming two different embryos, which will have the same genetic inheritance.
The children will be of the same sex and will be very similar.

Popular Posts

Category Pregnancy, Next Article

Caesarean section: scheduled cesarean - Pregnancy

Caesarean section: scheduled cesarean

In which cases is a caesarean section proposed? A little less than half of cesarean sections performed in France are scheduled either because of the mother or because of the child. The reasons can be multiple. These caesareans programmed , that is to say planned more or less in advance. The most common causes of scheduled cesarean section related to the mother A caesarean will be scheduled, for example: If the mother presents a local mechanical pathology as a uterus weakened by a previous intervention
Read More
5th week of pregnancy (7 weeks) - Pregnancy

5th week of pregnancy (7 weeks)

The 5th week of pregnancy introduces the 2nd month of pregnancy , a key period for the baby to become, for the formation of its organs. Also, it is important for the mother to protect herself from microbes (such as listeria), viruses (such as rubella) and parasitic diseases (such as toxoplasmosis) during this period, as egg aggression at this key stage of pregnancy can have serious consequences for the fetus and its development
Read More
Lose weight after pregnancy - Pregnancy

Lose weight after pregnancy

The young mother you are discovering the joys of motherhood. But sometimes, a look in the mirror makes you regret your figure before, and these kilos-memories of the pregnancy you worry a little. Be reassured: you are not alone with your concern. Having a baby changes your life, and it changes the body, and it takes time for the body to regain some balance
Read More
How is milk made in the breasts?  : lactation - Pregnancy

How is milk made in the breasts? : lactation

The lactation process depends on two hormones: prolactin and oxytocin. Both are activated by the baby's sucking. > Prolactin : this hormone is secreted after birth and causes the rise of milk. It triggers the manufacture of milk at the level of the alveoli of the breast, when the baby heads. Prolactin levels are higher at night, allowing nocturnal feedings
Read More