Sex Selection

In the modern world, chances to have a child are limited, as are resources.
Many families cannot have many children, so it is becoming more and more common to try to balance the family.
At our hospital, we have a sex selection method for such people.
It is important to remember that no method of sex selection is perfect.
In a natural pregnancy, there is a 50% chance that a baby of the desired gender will be born, so as a general rule, we recommend that you start sex selection from the second child.

Underlying Biology

The sex of a baby is determined by the type of sex chromosomes that sperm cells have.
The sex chromosome of an oocyte is always the X chromosome, but there are two types of sperm: sperm with the X chromosome (X sperm) and sperm with the Y chromosome (Y sperm).
When an oocyte binds to X sperm, a girl (XX) is born, and when it binds to Y sperm, a boy (XY) is born.
Therefore, in the case of a birth separation, we consider ways to make it easier for the sperm of the desired gender to meet the oocyte.

X sperm are resistant to acidity, and Y sperm are resistant to alkalinity.
In addition, X sperm is about 7% heavier than Y sperm.

A woman's vagina is always filled with a strong acidic solution to prevent the invasion of germs from the outside.
The inside of the cervix and the inside of the uterus, which is further back from the inside of the vagina, is alkaline.
As the day of ovulation approaches, the cervix secretes even stronger alkaline solution.

There are about twice as many Y sperm as X sperm in the ejaculated semen.
Nevertheless, the proportion of men and women born is about the same.
This is because the vagina is acidic and many Y sperm perish quickly.
However, in the cervical canal and inside the uterus, Y sperm will be more advantageous and the ratio of males and females born as a result will be a match.

Sex Selection Methods

Pink Jelly / Green Jelly

Pink Jelly A buffering jelly that keeps the vagina moderately acidic so that X sperm have a higher rate of survival.
Green Jelly It is a jelly to increase the alkalinity in the vagina so that Y sperm can survive more easily.

The ingredients of these jellies are harmless to the human body and have been well-confirmed for their safety.


It is calcium phosphate. A dietary supplement taken to increase the birth rate of boys.
It is a natural calcium containing a small amount of iron and has no side effects.
It was not originally developed for sex selection, but if you take Lincal, there is an 80% chance that a boy will be born.
It is not clear why the birth rate of boys increases, but it can be supplemented with calcium and has no side effects or fetal effects, so it is prescribed for those who wish to give birth to boys.

Percoll Method

This is a method of separating X sperm and Y sperm by taking advantage of the fact that X sperm is about 7% heavier than Y sperm.
The sperm sample is separated by density.
Artificial insemination or in vitro fertilization is performed with the sperm collected underneath for sex selection of girls.
For sex selection of boys, artificial insemination or in vitro fertilization is performed with the sperm collected on the top.

Pink jelly, green jelly and lincal are used in combination with the timing method, and Percoll method is used in combination with artificial insemination or in vitro fertilization (mainly micro-insemination).