Are there more boys or girls born after fertilization in vitro (IVF)?

Periskopi

2 November 2025, 23:46(8 months ago)

Scientists find that the rate of embryo development, selection algorithms, and even artificial intelligence can affect the gender composition of babies born through IVF when couples plan to have children, most believe that chances for girls or boys are equal to 50:50. However, in cases where pregnancy is achieved through fertilization [...]

When couples plan to have children, most believe that chances for a girl or boy are equal to 50:50. However, in cases where pregnancy is achieved through in vitro fertilization (IVF), the possibility of a baby being a boy is greater.

Researchers have found that male embryos develop a little faster, so they are chosen more often to move to the womb. That's why the chances of a couple making IVF having a boy amount to 56 out of 100 cases.

When we link the fastest development to the best quality, we unconsciously select male embryos”, explains Dr. Helen O'Neill, fertility specialist at London University. “The devices we use to select embryos favour the male gender”.

Why male embryos are the fastest “”

Male embryos carry X and Y chromosomes, while feminine ones carry two X chromosomes. This extra X to female embryos brings an additional process of “reactivating” of an X chromosome to maintain genetic balance, the process that requires more energy. Hence, female embryos develop more slowly in their early stages. As a result, in IVF, where embryos are selected according to the rhythm and order of development, male embryos have a small advantage, which increases the likelihood of being chosen for transfer, the Daily Mail notes.

Artificial intelligence can also favor male embryos

Dr. O'Neill and her team have conducted a study of 1,300 embryos, whose gender was previously known through genetic testing. The embryos have been praised by doctors and two artificial intelligence systems (AI), which use “time-lapse” of embryo development.

The results showed that:

When doctors made the selection, 69% of male embryos were estimated to be best quality “, compared to 57% of female embryos.
One of AI's systems also showed slight tendencies toward male embryos, while the other was neutral. Although differences are minor, they are enough to create a slight gender trend in embryo selection statistics.

Does a mother's age affect her child's gender?

Another interesting study by Harvard University analyzed more than 58,000 mothers and found that the mother's age at the birth of her first child can affect the gender makeup of offspring.

Women who were born for the first time before 23 years were 34% likely to have children of the same gender. That figure grew to 43% after the age of 28.

The authors concluded that as the mother's age grows, so do the likelihood of all children being of the same gender, while genetic and demographic factors had less impact.

How the IVF Works

In vitro Fertilization (IVF) is a medical procedure in which the egg cell is engaged outside the body, in a laboratory, and then the embryo is transferred to the womb. This method is used for couples who have difficulty conception and may include donated eggs or sperm. After the transfer of the embryo, pregnancy develops naturally, just as in natural conception.

IVF's success depends on women's age and the causes of infertility, if they're known. According to statistics, average chances of successful pregnancies per cycle IVF are:

Under 35 ʹ 29%
From 35 to 37
From 38 to 39
From 40 to 42

This finding points out that even in the technological processes of assisted reproduction, biological factors remain crucial and that artificial intelligence, however seemingly neutral, can reflect natural gender trends that occur in earlier stages of life. /Periscopi/