When is the baby's gender determined? What determines the baby's gender?

In the days when science was not well developed, people generally imagined that whether to have a boy or a girl was determined by women. In fact, from a scientific point of view, is it really determined by the mother whether to have a boy or a girl? What are the factors that affect the gender of the baby?

When is the baby's sex determined?

The sex of the baby is determined when a sperm combines with the egg, which means that the sex of the baby is determined when pregnancy is discovered after intercourse. So hundreds of millions of sperm enter the female reproductive tract, and sperm with different sex chromosomes have an equal chance of entering the egg. No one can know in advance which type of sperm will eventually combine with the egg.

What determines the sex of a baby?

It is determined by genetic factors. At the genetic level, the SRY gene is generally used as a sex-determining gene, that is, if there is an SRY gene, it will develop into a boy, and if there is no SRY gene, it will develop into a girl. Studies have found that SRY is actually just one of the many genes that affect gender development. Chromosome determination At the chromosome level, humans have 23 pairs of 46 chromosomes, of which 22 pairs of 44 chromosomes are called autosomes, which mainly regulate the development of the body, and those related to gender development are called sex chromosomes, usually expressed as "X" and "Y". The karyotype of the sex chromosomes of a normal male is: 46, XY; the karyotype of the sex chromosomes of a normal female is: 46, XX. It is generally believed that if there is a Y chromosome in the chromosomes of a human embryo, it will develop into a boy; if there is a Y chromosome, it will develop into a girl.

It is unscientific to use test strips to test the sex of the fetus

Urine testing of baby's gender is unscientific, unreliable, and unacceptable!

Searching the keyword "intelligender" on Sina Weibo, many bloggers who "buy from overseas" immediately appear. The price of the test strips ranges from 150 to 600 yuan. According to the introduction of many bloggers, the test strips have obtained the US FDA (Food and Drug Administration) certificate and are available in major shopping malls and pharmacies in the United States. The accuracy rate can reach 90%. Pregnant women who are 10 weeks pregnant only need to drop morning urine on the test strip and wait for 5-10 minutes, and the color of the test strip will change. If the test strip is orange (pink), then the baby is a girl; if the test strip is green (blue), then the baby is a boy.

Looking through the comments on these overseas purchasing agents' Weibo, there are many comments from professionals, saying that this test strip determines the sex of the fetus by testing the level of male hormones in human chorionic gonadotropin (HCG). However, although HCG can be detected through urine, it is unscientific to use the secretion of male hormones (testosterone) contained in HCG to determine the sex of the fetus.

Tian Yuqin, chief physician of the obstetrics department of the First Affiliated Hospital of Kunming Medical University, told reporters: "It is very unscientific to use urine to test the baby's gender. Even if it is a girl, there will be a certain level of testosterone secretion. If it is a boy, the amount of testosterone secretion may not be particularly high." She also introduced that the pregnant woman's own hormones will also interfere, making the test results of the test paper even more inaccurate. Pregnant women must not completely trust this kind of test paper, and it is even more undesirable to use this result to decide whether the fetus should stay or go.

Seven accurate scientific methods

1. Ultrasound scan

Ultrasound is a type of sound wave, and reports so far show that it has no adverse effects on the fetus, so it is very commonly used in the obstetrics and gynecology community.

When using ultrasound to diagnose the sex of a fetus, the accuracy for a boy can reach over 95%, while the reliability for a girl is only about 85%.

2. Amniocentesis

Amniocentesis is mainly used to diagnose whether the fetus has chromosomal or neural tube defects. It is usually performed between 16 and 20 weeks of pregnancy. Since the chromosomes of the fetus can be known, the sex of the fetus can also be known. The accuracy can reach 99%, but there is a 1% chance of miscarriage. Therefore, the medical community does not approve of performing amniocentesis just to determine the sex of the fetus.

3. Chorionic villus sampling

Also known as "chorionic villus sampling", it is usually performed at 8 to 10 weeks of pregnancy. The main purpose is the same as amniocentesis, which is to diagnose whether the chromosomes of the fetus are normal, but some people also use it to diagnose the sex of the fetus. The accuracy rate can reach 98%.

Although chorionic villus sampling can determine the sex of the fetus around 10 weeks of pregnancy, it can cause miscarriage (3% to 5%) and may harm the fetus, causing its hands and feet to be mutilated. Therefore, it is best not to undergo this test just to determine the sex of the fetus.

4. Uterine flushing with saline

This is a relatively practical method of its kind in recent years, usually performed at 9 weeks of pregnancy. So far, it has been proven to be quite safe, with a reliability of 98%. However, this test can only determine the gender of the fetus, but cannot tell whether the chromosomes of the fetus are normal. In addition, sexual intercourse should not be performed within a week before the test to reduce errors.

5. Blood test

Genetic engineering technology can be used to collect blood from the mother to determine the sex of the fetus. Although there is no danger to the fetus, and some testing units claim that the reliability is 95%, according to the clinical data and evidence obtained by the author, the error rate is quite high. Therefore, it is not a reliable and practical method.

6. Fetal cell sex chromosome examination

Check the fetal cells for sex chromosomes, namely X-bodies and Y-bodies. Chromosomes can only be seen when cells divide. In cells, chromosomes are dispersed into chromatin. In female cells, they are often seen in the chromatin.

Under the microscope, sex chromatin bodies, or Bartholin bodies, were first observed by Barr in 1949. They are small, specific, condensed, and darkly stained chromatin blocks that appear close to the nuclear membrane of the cell nucleus.

In human cells, only one X chromosome is active, and the inactive X chromosome forms sex chromatin. Normal male cells have no sex chromatin, while normal female cells have one sex chromatin.

Sex chromatin can be easily observed in stained smears of oral or vaginal epithelial cells. In polymorphonuclear leukocytes, sex chromatin looks like a drumstick, usually called a drumstick body. The presence or absence of Bartholin bodies or drumstick bodies is an important basis for identifying male and female sex.