By Cristina Mestre Ferrer BSc, MSc (embryologist).
Last Update: 09/24/2014

During the third month of pregnancy you could start noticing a bigger volume of your abdomen and breast. This month is really important for the parents, because they can start having some information about their baby’s health.

In this month, the embryonic period ends and starts the fetal period, where the embryo turns into a fetus: in the future baby there are already all of his organs, even if they will have to come to complete development.

The different sections of this article have been assembled into the following table of contents.


  • The new baby grows from a length of 1,3 cm, ate the beginning of the third month of pregnancy, to approximately 8,5 cm.
  • His weight is between 15 and 20 grams.

During this month, male and female genital organs are forming, even if it is not easy to define the sex through ultrasounds.

Sickness is normal in this period, but you can avoid vomiting through eating small and continual quantities of food, during all the day. This will also benefit your state, and you will fell stronger and with more energy.

Fetal development

The future baby’s movement during this month is more active, although you can’t barely notice it. In this period you will know the sex of the baby, even if it will be difficult to confirm it through ultrasounds. He kicks, turns his ankles and wrists, clenches his fists, bends his toes up and down, frowns, purses his lips and makes other facial movements. He swallows the amniotic fluid, then regurgitates it by his mouth, or replace it through his bladder.

The fetus (we will call him this way from now on) is very similar to a human being: his limbs are longer, and his hands are more clearly defined throughout the development and the separation of the fingers. You could also recognize his ears.

Let’s see the baby’s development week by week, during the third month of pregnancy. In this way we could get to know the evolution that is slowly taking place in these days.

Nine weeks pregnant

The fetus is still very small, approximately like a grape; as we said at the beginning, every day he’s more similar to how he will look like once born, and his evolution, from now, will be faster: that little grape will grow in weight and size before you expect it.

In this weeks he is 2,5 cm long more or less. His tail disappeared and his ears will be formed by the end of this week; his nose is also formed. His eyes have developed enough to have a human shape, still he won’t be able to open them until the 27th week approximately.

The ultrasounds will be the very protagonist, and you will be able to listen to your baby’s heart beating for the first time.

Nine weeks fetal development

Ten weeks pregnant

The fetus joints are defining at a high speed, like his muscles, although they will be totally formed by the end of the month, during the following week.

During these days, it is normal your doctor makes you several tests to be sure everything is fine, like for example checking your weight, your blood pressure, or a test of your abdomen, or a urine test.

You will notice your stomach swelling more and more: your uterus has expanded and filled almost all your abdomen.

Eleven weeks pregnant

This week’s news is the umbilical cord, which takes centre stage because blood starts flowing through it. This blood circulation through your body can make you feel some cramps, due to a lack of potassium.

The fetus is totally formed, his face has formed very fast and you could start and recognize him: your baby has defined features. Also the placenta is formed and brings all the necessary cells and hormones to the fetus.

You could notice your nails and hair grow faster than before: it is all part of the physiological hormonal change your body is living.

Medical checking

Twelve weeks pregnant

During the 12th week of pregnancy, your baby has reflexes: even if you can’t feel his movement yet, he moves energetically, during this week he will develop his reflexes, and you will be able to play with him by touching your stomach.

Among the reflexes he develops, there will be sucking: he will start and putting his finger into his mouth and learn how to suck, which will be very useful, once born, to feed himself through the breastmilk.

Another important moment of this week is the fetus genitals development.

His measures are around 5 cm, with a weight of 14 grams.

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Authors and contributors

 Cristina Mestre Ferrer
BSc, MSc
Bachelor's Degree in Biological Sciences, Genetics & Human Reproduction from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Embryologist at IVI Barcelona. More information