When and how can you know for sure if it will be a boy or a girl?

By (embryologist), (embryologist) and .
Last Update: 04/04/2023

It is true that some couples make the decision that they do not want to know the sex of their baby during pregnancy and, therefore, find out whether it is a boy or a girl at the time of delivery. However, this is not the most common, but the couple, after learning that the baby is well, is curious to know if they are expecting a boy or a girl.

In addition, many couples find it advantageous to know the sex of the baby before the baby is born, believing that a greater connection will be established by naming the baby, planning the room decorations, etc.

However, there are many myths about this subject and home methods have emerged, with no scientific basis, to predict whether the baby will be a boy or a girl. These methods are based on beliefs passed down from generation to generation and must be performed as a game, since, in order to know the sex of the baby reliably, one must resort to a scientific method.

Home methods for predicting the sex of the baby

There are different myths about how to predict the sex of the baby. These myths and popular beliefs have no scientific basis, so your probability of being correct will be 50%.

Among the most commonly used home methods to know if the baby will be a boy or a girl are the following:

  • Belly shape. If the pregnant woman's belly is more rounded, it is said to be a girl. On the other hand, if it is pointed, child.
  • Ring method. It consists of tying a rope to a ring, as if it were a pendulum. The pregnant woman lies down and another person holds the rope over her belly. If the ring moves from side to side, it is believed to be a boy. Conversely, if the ring makes circles, a girl.
  • Oil test. The pregnant woman lies down and someone pours a few drops of oil (e.g. olive oil) on her belly. If the oil does not move or advances slowly, this method says that a girl is expected. If the oil falls quickly, a child.
  • Bicarbonate test. The first morning urine of the pregnant woman, collected in a cup, should be used. Prepare another glass with the same amount of baking soda and mix. If the result bubbles, it is supposed to be a boy and, if nothing happens, a girl.
  • Cravings. It is also thought that if the pregnant woman is in the mood for sweets, she is expecting a girl, while if she prefers salty foods, it will be a boy.
  • Nausea and headache. Popular belief says that, if there is a lot of nausea, the baby is a girl. On the other hand, if the woman has a headache, it will be a boy.
  • Face shape. If the shape of the pregnant woman's face changes and becomes rounder, the baby is believed to be a girl.
  • Body hair. If the body hair grows faster, it is said that it will be a boy, as well as if the pregnant woman has silkier and prettier hair.
  • Cold feet. If the pregnant woman has this discomfort during pregnancy, she could be expecting a child.
  • Baby's heartbeat. It is also said that if the baby's heart has more than 140 beats per minute, it will be a girl. If the number is below, child.
  • Chinese table and Mayan table. Based on the age of the woman when she becomes pregnant and the month in which the baby is conceived.

These home tests do not pose any risk, so some pregnant women decide to perform them as entertainment and, thus, see which result has obtained more points in favor, boy or girl. However, the results should be interpreted as a game, as these methods of sex prediction lack scientific evidence.

Blood test to determine the sex of the baby

There is the possibility of performing a blood test on the pregnant woman, which would allow us to know the sex of the baby from the 8th week of gestation. The explanation is that fragments of fetal DNA can be found in maternal blood.

The maternal blood sample is sent to the laboratory. There, it is analyzed for the presence of the Y chromosome to determine if it is a boy (if this chromosome is found) or a girl (if the Y chromosome has not been detected).

This type of non-invasive prenatal testing is more commonly known because it also allows, from the maternal blood sample, to analyze certain chromosomes of the baby, especially when there is a high risk of an abnormality. However, due to its non-invasive nature, it is a test that does not need this indication to be performed.

You can find more information about these non-invasive prenatal tests at the following link: Non-invasive prenatal maternal blood test: advantages and indications.

Chorionic biopsy and amniocentesis

Invasive tests such as chorionic villus sampling or amniocentesis can also accurately reveal the sex of the baby. Chorionic villus sampling is usually performed between 11-13 weeks of pregnancy, while amniocentesis is not performed until 15-20 weeks.

However, as these tests are invasive and even have a certain risk of gestational loss, they are only used to determine the presence of genetic abnormalities in the fetus (when there is a risk of these alterations) and not only to determine the sex of the fetus.


Ultrasound or ultrasound is the most common test to find out the sex of the baby on the way, as it is a non-invasive and safe method. However, it is necessary to wait patiently until the second trimester ultrasound to know the sex accurately.

This second trimester ultrasound is usually scheduled for the 20th week of gestation, although the fetal sex may be revealed a few weeks earlier. Therefore, during this ultrasound, the sex of the baby can be revealed with great reliability, as well as being used to evaluate many other things.

However, in order for the specialist to determine the sex of the baby, the fetal position must allow the genitalia to be well observed. Thus, if the scrotal sac and penis are distinguishable, it is a boy. On the other hand, the gynecologist will determine that it is a girl if he does not observe male genitalia or if he can see the labia majora.

FAQs from users

What is the Ramzi method to know the sex of the baby?

By Silvia Azaña Gutiérrez B.Sc., M.Sc. (embryologist).

The Ramzi method is a method that can be used to predict by ultrasound, as early as 6-8 weeks of pregnancy, the sex of the baby.

This method is based on the position of the placenta within the uterus, which, because of the polarity of the chromosomes, is to the right if it is a boy or to the left if it is a girl.

However, this method is not sufficiently accepted and it is usual to wait for the ultrasound scan in the 20th week of pregnancy to know the sex of the baby with great precision and probability of success.

Can the shape of the pregnant woman's belly indicate the sex of the baby?

By Sarai Arrones BSc, MSc (embryologist).

It is often said that if the belly is round, it will be a girl and if it is rounder, it will be a boy, but this is just a myth. There is no relationship between the shape of the abdomen and the sex of the fetus.

The appearance will depend on whether the woman is primiparous or multiparous, the constitution of her body, the shape of her uterus and the size of the fetus.

Can I know the sex of the baby in the 17th week of pregnancy?

By Silvia Azaña Gutiérrez B.Sc., M.Sc. (embryologist).

In the 17th week, it is possible that they can already tell you the sex of the baby. However, in the Social Security, this ultrasound is performed a little later, around the 20th week of pregnancy.

However, there are other methods by which the sex of the baby can be known as early as week 17.

Suggested for you

Ultrasound is a very important test during pregnancy, not only because it is the usual method to know the sex of the baby. If you want to read more about this test, we recommend you to visit this link: How is fetal ultrasound in the first, second and third trimester?

On the other hand, if you want to know more about amniocentesis, you can access the following article: Amniocentesis: what are its indications and possible risks?

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FAQs from users: 'What is the Ramzi method to know the sex of the baby?', 'Can the shape of the pregnant woman's belly indicate the sex of the baby?' and 'Can I know the sex of the baby in the 17th week of pregnancy?'.

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Authors and contributors

 Sarai Arrones
Sarai Arrones
BSc, MSc
Bachelor's Degree in Biomedicine and Biomedical Sciences from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Specialist Training Course of gamete, embryo, and animal tissue cryopreservation. Embryologist specializing in the field of Assisted Procreation. More information about Sarai Arrones
 Silvia Azaña Gutiérrez
Silvia Azaña Gutiérrez
B.Sc., M.Sc.
Graduate in Health Biology from the University of Alcalá and specialized in Clinical Genetics from the same university. Master in Assisted Reproduction by the University of Valencia in collaboration with IVI clinics. More information about Silvia Azaña Gutiérrez
License: 3435-CV
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