When Can You Tell the Sex of a Baby?

When Can You Tell the Sex of a Baby? a pregnant belly

Is it a boy or a girl? This question is of great interest to all future parents. Nowadays, married couples do not always rely on calculations in planning the gender of a baby, but they want to know who will be born when it is already possible to determine this by ultrasound. So, when can you tell the sex of a baby?

Why Do Future Parents Want to Know the Gender of the Expected Baby?

Every family that is expecting a child has a need to prepare all the necessary diapers, clothes and baby linen before the birth of the baby. The list of things necessary for the baby is very long. It includes a crib, a stroller, a bath, and many other items. What colors should parents choose: pink with flowers or blue? It depends on the sex of the baby. Determining the gender of the child is also very important when there are genetically transmitted diseases in the family. This is also a widespread case when parents want to know the sex of their child.

Physiology of the Formation of the Sex of the Child

Practically every future mom, with rare exceptions, seeks to find out the sex of her child as soon as possible. The most reliable method is ultrasound, and it gives the most accurate information.

Despite the existence of many signs, beliefs and folk methods, only the male sex cells (spermatozoa) can affect the gender of the future baby. They determine whether there will be a boy or a girl, since only these cells can be carriers of the female set of chromosomes (XX) or male (XY).

When Can You Tell the Sex of a Baby? its a boy - girl

Who will be born, is determined immediately at the moment of conception. It depends on what sperm could get to the egg and fertilize it. XX carrier guarantees the birth of a girl, XY carrier – a boy. Nothing depends on a woman in the matter of planning the gender of the baby.  A female chromosome set is always the same – XX.

When Can You Tell the Sex of a Baby?

Future fathers and mothers are often interested in how accurately you can find out the sex of a baby in the first trimester. Keep in mind that the fetal genitals begin to form from the sixth week of pregnancy. Then there is a small bump on the site of the baby’s genitals. Until the ninth week, these bumps in boys and girls look the same, without noticeable differences due to their small size.

After 11 weeks in boys, this bump changes into a penis. At the 13th week of pregnancy, under the action of the hormone dihydrotestosterone, his intimate organ begins to grow. The testicles at this stage are located in the stomach. In the scrotum, they descend only at 7 months of pregnancy. Therefore, at 11 weeks on an ultrasound examination, the doctor may only assume the gender of your child. The probability of error at this time is 50%. Therefore, despite the great desire of parents, during the first ultrasound at 12-13 weeks, it is still difficult to determine the exact sex of your baby.

When Can You Tell the Sex of a Baby? ultrasound-transducer

Very often in this period, swelling of the genital lips of girls can be mistaken for a male penis. And it also happens that the tightly closed legs of a child simply close the genitals. Very experienced ultrasound specialists on a good machine can determine the sex of the unborn baby at week 14. To do this, a doctor measures the angle between the genital tubercle and the back of the baby. In boys this angle is 300 or more, in girls it is less than 300.

Sex Determination

At a period of 18 weeks, we can talk about a more accurate determination of the sex of the child. At this time, it is easier to determine a boy.

So, when can you tell the sex of a baby? The best time to accurately determine the sex of a baby is the 20-24th week of pregnancy. The fetus in this period is already very mobile. The sex differences of boys and girls are distinguishable. That is why at the second planned ultrasound you have a chance to find out who will be born. Why just chances? It often happens that the child takes an uncomfortable position as if turning away from the doctor and it is difficult to determine the baby’s gender. This rarely happens. But in most cases, one of the results of the second planned ultrasound will be the determination of the sex of the child.

There is no need to be upset if your baby “did not allow” to determine the gender. The main thing is that the baby is healthy. And future mom and dad can come up with two names, or buy things in neutral colors.

When Can You Tell the Sex of a Baby? Ultrasound Pregnancy

It should be noted that there is a technique of very accurate results of determining the sex of the child. This is a 3D ultrasound. It is rather expensive and, as a rule, is carried out in medical centers.

Other Ways to Determine the Gender of the Child

There are the most accurate methods for determining the sex of the child. The first is a non-invasive DNA test, which allows determining the sex of the baby from 8–9 weeks of gestation with an accuracy of 99%. The method is based on the extraction of DNA from fetal erythrocytes, which by this time begin to be determined in the blood of a pregnant woman. Such an analysis is considered a new method. It is carried out only in paid centers and clinics, and it is rather expensive.

Invasive methods are based on penetration with a thin surgical instrument into the uterus (in the ovum), in order to take the analysis of water, parts of the skin of the fetus, and blood. An early biopsy of the chorionic villi is done. The resulting material gives a complete and accurate (99.9%) idea of ​​what sex a baby is in the womb. However, such a test is performed only when there are suspicions of pathology and congenital diseases, in which case pregnancy will have to be terminated.

The second technique is carried out at a period of 16-18 weeks and is called amniocentesis. Through a small puncture a little amniotic fluid is also taken for the study of the chromosomal composition. The accuracy of the method is 99%. Cordocentesis is an invasive method in which fetus cord blood is taken for examination. Once again we recall that doctors resort to these methods only in exceptional cases.

When Can You Tell the Sex of a Baby? boy girl

In most pregnancies, it is possible to determine the exact sex of the child closer to the 24th week of pregnancy, at the second planned ultrasound scan, after the future mother first felt the movement of her baby.


Women who have already given birth to a child can assume the sex of the baby by comparing previous courses of pregnancy. Usually, if the current pregnancy is not at all the same as the previous one, then there is a high probability that the sex of the child will be different.

The peculiarities of pregnancy in a mother carrying a boy or girl have large characteristic differences, which she feels very well.

Considering the medical practice, we can call all the definitions for the future sex of the child conditional, because even an ultrasound can sometimes make mistakes in determining the sex of the baby.

While in the womb, the baby sometimes takes up such a position during the ultrasound scan that it is very difficult to recognize the gender. It happens that during every ultrasound the child “hides”. In this case, parents will find out the sex of their baby only after the birth.

But if you think well, then no matter what gender your baby is, the most important thing is that you finally have your baby and he/she is healthy.

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