What happens to the baby and the mother in the 20th week of pregnancy?

By (embryologist).
Last Update: 03/25/2024

The woman has reached the midpoint of her pregnancy at week 20, since it is estimated that around week 40 is when the due date is scheduled.

Although every woman and every pregnancy is different, the pregnant woman should have gained about 5 kg. However, the woman will begin to gain about half a kilo per week from this point on.

The baby will also grow and some facial features will develop. In addition, the baby will begin to notice outside sounds.

Changes in the baby in week 20

Throughout the 20th week of pregnancy, some features of the face, such as the nose, for example, will begin to form. In addition, the baby may begin to suck his or her thumb, as there is an improvement in the sucking reflex.

On the other hand, the pregnant woman will have to be careful with outside noises since the baby will start to be more sensitive to sounds. This could wake you up if you are sleeping.

Another event that takes place in the 20th week of pregnancy is the development of nipples in infants. If it is a girl, her mammary glands also develop.

During this week also begins the formation of the vernix caseosa, a fatty substance, which begins to lie under the skin, protecting it from the amniotic fluid. At birth, the baby is covered with vernix.

Prior to the 20th week of pregnancy, as the fetus had poorly developed legs that were closer to the body, it was measured from the beginning of the head to the end of the tail of the notochord.

At the end of this week, the fetus is about 20-25 cm long and weighs approximately 260-280 grams. From this moment on, the fetal measurement system changes. Now the fetus is measured from the beginning of the head to the toes.

What happens in the mother at week 20?

The uterus has grown and is at the level of the navel. In addition, it is common for the pregnant woman to have more heartbeats than usual, since the heart must pump more blood for the circulatory system to reach the placenta and the fetus. This also results in the need for deeper breaths.

The increase in weight together with the blood circulation makes women's legs feel very heavy, causing the appearance of varicose veins. It is recommended that the pregnant woman rest her legs on a regular basis, in addition to wearing comfortable (not tight) clothing. In case the woman wants to wear heels, these should not exceed 4 cm.

Another aspect to take into account is the amount of iron consumed by the mother. During pregnancy, iron is essential because it allows blood oxygenation. So include in your diet foods with high iron content such as red meat, legumes, fish, spinach and if the doctor considers it appropriate, he will recommend a vitamin complex.

Other symptoms in the mother

Tired and heavy legs, increased heart rate and the appearance of varicose veins are the most common symptoms described by most pregnant women in the 20th week of pregnancy. However, they are not the only ones.

Other common discomforts in the 20th week of pregnancy include the following:

  • Constipation.
  • Stretch marks.
  • Back pain.
  • Sciatica.
  • Burning.

It may also happen that the woman presents inflammation of her gums due to the action of hormones on the ligaments and tissues. This is why it is recommended that pregnant women see a dental specialist approximately every 3 months.

What is the morphological ultrasound of the 20th week like?

At this week of gestation, the first high-resolution ultrasound is usually performed. It is a test that provides an image that offers greater clarity than that offered by normal ultrasound scans.

Morphological ultrasound allows us to know the exact measurements of the fetus, but also to analyze each of the organs in detail.

Thus, the specialist will assess whether there has been any abnormality in fetal development. If so, it would be advisable to extend the study by means of an amniocentesis, for example.

FAQs from users

How are the baby's movements in the 20th week of gestation?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

During the 20th-22nd week of pregnancy, the baby begins to make flexion and extension movements of the limbs. Therefore, in these weeks of gestation, the mother will notice the typical little kicks of her baby in her abdomen. In addition, in thin women, they may feel these fetal movements even more.

When the baby turns fully, the pregnant woman may feel more pain than usual. As the baby grows, it will have less room to move freely and, therefore, the movements will be less jerky.

Is the sex of the baby known at the 20th week of pregnancy?

By Marta Barranquero Gómez B.Sc., M.Sc. (embryologist).

Yes, the sex of the baby can be known from the 13th week of pregnancy, although in some cases it is confirmed at the ultrasound at the 20th week of gestation. Much will depend on the position of the baby at the time of the ultrasound for sex determination.

Suggested for you

If you want to know more about how the next month of gestation will evolve, we recommend you to visit this article: 6 months of pregnancy: characteristics and symptoms.

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

🙏 Please share this article if you liked it. 💜💜 You help us continue!


A Frković, L Randić, M Krstulja. Fetal death in the 20th to the 36th week of pregnancy. Jugosl Ginekol Perinatol. Jan-Apr 1990;30(1-2):23-6.

C Everett. Incidence and outcome of bleeding before the 20th week of pregnancy: prospective study from general practice. BMJ. 1997 Jul 5;315(7099):32-4. doi: 10.1136/bmj.315.7099.32 (Ver)

Elena Figuero, Yiping W Han, Yasushi Furuichi. Periodontal diseases and adverse pregnancy outcomes: Mechanisms.Periodontol 2000. 2020 Jun;83(1):175-188. doi: 10.1111/prd.12295.

FAQs from users: 'How are the baby's movements in the 20th week of gestation?' and 'Is the sex of the baby known at the 20th week of pregnancy?'.

Read more


 Marta Barranquero Gómez
Marta Barranquero Gómez
B.Sc., M.Sc.
Graduated in Biochemistry and Biomedical Sciences by the University of Valencia (UV) and specialized in Assisted Reproduction by the University of Alcalá de Henares (UAH) in collaboration with Ginefiv and in Clinical Genetics by the University of Alcalá de Henares (UAH). More information about Marta Barranquero Gómez
License: 3316-CV

Find the latest news on assisted reproduction in our channels.