Week 15 of pregnancy: boy or girl?

By (embryologist), (embryologist) and (fertility counselor).
Last Update: 05/04/2022

Week 15 of pregnancy is usually a quiet week for the expectant mother. Chances are you have shared the news with family and friends, and you will feel more relaxed.

In addition, the uncomfortable symptoms of the first weeks of gestation will have disappeared, as will the risk of miscarriage.

The baby continues to develop very quickly and, if an ultrasound scan is performed in the 15th week of pregnancy, it may be possible to tell whether it is a boy or a girl.

Changes in baby

From the 15th week of pregnancy, the muscles and bones of the fetus will begin to develop at a much faster rate, so their size will double.

At 15 weeks, the fetus is about 10-12 cm long and its weight can reach 50-70 g.

As for the changes that the baby's body undergoes during this 15th week of gestation, we highlight the following:

  • The hair on the head and eyebrows becomes thicker.
  • The neck becomes longer and the baby can separate its head from the chest.
  • The muscles of the face already exercise the sucking movement, so the thumb can be sucked. This prepares his muscles to feed on his mother's milk when he is born.
  • Vocal cords are formed, although the baby will not use them until birth.
  • The spinal cord is now fully formed.
  • His hearing is almost developed, so he can pick up sounds and his mother's voice.
  • The sense of taste develops and the baby can perceive different flavors that reach the amniotic fluid through the placenta.
  • The fetus begins to move more and more inside the amniotic sac to strengthen its muscles. In the ultrasound scans, it can be seen how it changes position.
  • Ossification begins: bones retain more calcium and become stronger.

Symptoms in the mother

The 15th week of pregnancy, and in general the entire fourth month, is the best stage for the woman. The nausea has disappeared, he still does not feel fatigue and everything seems to be very normal.

Even so, the mother's body continues to undergo changes due to pregnancy and the following signs and symptoms may be noted:

  • As the belly grows, a brown line may appear from the navel to the pubic area, known as the linea abba linea alba. This line is created by an increase in melanin (skin pigment) production due to high estrogen levels.
  • Nipples, moles, freckles and birthmarks are also darkened by the activation of the skin's melanin-producing cells.
  • The skin is more sensitive and spots or darker areas may appear. This is what is known as chloasma gravidarum.
  • The nose may remain stuffy due to inflammation of the mucous layer of the nasal passages, which respond to increased estrogen. This discomfort is called rhinitis of pregnancywhich is very common and can be relieved with steam baths.
  • Blood circulation and excess weight on the legs can lead to the appearance of the first varicose veins or varicose veins.
  • The woman's mood is usually good, although it is normal to have mood swings due to hormonal fluctuations and minor organizational or memory problems.


Week 15 of pregnancy may be a good time to start exercising if you have not started before. The woman will not be as tired as in the first weeks of gestation and will have regained energy, so it is necessary to make an effort to keep in shape.

Swimming, pilates, yoga or walking are good options if the woman did not practice any sport before.

As we have said, pregnant women's skin is very sensitive and undergoes many changes. Therefore, it is very important to avoid sun exposure, moisturize the skin well and use sunscreen.

It is also important to drink plenty of water throughout pregnancy, since, in addition to promoting hydration, it improves blood circulation.

Pregnancy Control

From the first moment a woman discovers she is pregnant, it is important to start a follow-up of the entire pregnancy according to what is established by the Spanish Society of Gynecology and Obstetrics (SEGO).

This prenatal control consists of tests, ultrasounds, blood tests, weight control, etc., which should be done in different months of pregnancy.

What is the sex of the baby?

The second trimester ultrasound should be done between 18-22 weeks of gestation in order to evaluate all parts of the baby's body. This is the so-called morphological ultrasound, which also confirms the sex of the fetus.

However, in the case of an ultrasound scan in the 15th week of pregnancy, it would already be possible to see whether the baby is a boy or a girl, as its genitalia are already fully formed.

Normally, women with private insurance have more ultrasounds than those established by the public system and can find out the sex of their future baby sooner.

Second trimester screening

If the first trimester triple screening test has not been performed, it is still possible to do a combined screening in the second trimester to detect possible malformations or chromosomal abnormalities, although it is not as sensitive as the first one.

To perform this test, it will be necessary to perform a blood test on the mother and determine the values of alpha fetoprotein (AFP), beta-hCG and estriol (E3).

In case of an altered result and risk of congenital diseases, it will be necessary to confirm the diagnosis with an amniocentesis, since at 15 weeks of pregnancy it is too late to perform a chorionic villus sampling.

If you want to learn more about this invasive prenatal test, you can access the following article: Amniocentesis: Indications and Possible Risks.

FAQs from users

How many months is 15 weeks of pregnancy?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

The 15th week of pregnancy is equivalent to the third week of the fourth month of gestation.

In addition, week 15 is also considered the second week of the second trimester of pregnancy.

I am 15 weeks pregnant and I can't feel my baby, should I worry?

By Rebeca Reus BSc, MSc (embryologist).

If the results of the medical controls have been favorable, you should not worry, since all fetuses have their own pace of development. In addition, in the case of first-time mothers, it is still early to notice the movements of the future baby. If it is not the first pregnancy, you may already notice some fetal movement, but at this stage of development it does not have to happen either.

How tall is the baby at 15 weeks of pregnancy?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

Each baby has its own pace of development, but the normal size is between 10 and 12 cm in the 15th week of gestation, the size of an orange.

Suggested for you

Soon you will be 16 weeks and the pregnancy will be more noticeable. We recommend that you continue to learn more about the changes in the baby and the mother-to-be in the following article: Week 16 of pregnancy.

If you want more information about the control tests performed throughout the gestation period, you can access the following post: Prenatal pregnancy control.

We make a great effort to provide you with the highest quality information.

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Cunningham F, MacDonald P, Gant N et al. (1996). Adaptación maternal al embarazo. Masson SA. Cunningham F, MacDonald P, Gant N, et al. 4ª ed, Barcelona; pp. 201-237

González Merlo J. (1992). Modificaciones fisiológicas producidas en el organismo materno por el embarazo. En: Williams. Obstetricia (4.a ed.). Barcelona: Masón.

National Health Service (NHS) (UK) (2009). The Pregnancy Book. Your complete guide to: A healthy pregnancy, Labour and childbirth, The first weeks with your new baby. Crown copyright 2009. Produced by COI for the Department of Health.

Health Service Excecutive (Feidhmeannacht na Seirbhíse Sláinte) (2010). A guide to your pregnancy month by month. Breastfeeding.ie - Your breastfeeding support network. Order Code: HPM00341

The American College of Obstetricians and Gynecologists (2011). Frequently Asked Questions (FAQ156). Pregnancy.

FAQs from users: 'How many months is 15 weeks of pregnancy?', 'I am 15 weeks pregnant and I can't feel my baby, should I worry?' and 'How tall is the baby at 15 weeks of pregnancy?'.

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Authors and contributors

 Rebeca Reus
Rebeca Reus
BSc, MSc
Degree in Human Biology (Biochemistry) from the Pompeu Fabra University (UPF). Official Master's Degree in Clinical Analysis Laboratory from the UPF and Master’s Degree about the Theoretical Basis and Laboratory Procedures in Assisted Reproduction from the University of Valencia (UV). More information about Rebeca Reus
 Zaira Salvador
Zaira Salvador
B.Sc., M.Sc.
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Sandra Fernández
Sandra Fernández
B.A., M.A.
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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