The Twelfth Week of Pregnancy

By (embryologist) and (fertility counselor).
Last Update: 07/16/2014

As mom-to-be, you might notice your hair and nails are growing faster. That is a consequence of the hormonal change you are undergoing. Many women say the condition of their hair and nails is better than ever, as the hair is brighter and the nails get stronger.

Provided below is an index with the 3 points we are going to expand on in this article.

Changes in the mother

Your skin is also changing: now it looks more radiant and luminous due to physiological reasons. That is the reason why many people compliment your pregnant look.

You'd better enjoy the moment and feel happy. The happier you are, the happier you baby is.

Changes in the fetus

In the 12th week, the face has a human aspect and the chin has grown. The ears still are lower than they should be and the nails start to grow.

The genitalia has either male of female features, depending on the gender of the unborn, although they are not fully developed and discerning the gender is still kind of difficult.

If the embryo has two X chromosomes (XX), it will be a female, and therefore the clitoris may be already formed, both the labia majora and minora. A XY embryo corresponds to a male. In such case, the scrotum and the glans of his penis are formed. We have to bear in mind that we talk about genitalia formation, not development, that is why it is so hard to tell them apart in an ultrasound scan.

At the end of this week, the fetus is 85 mm long and weights 15-20 gr.

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 Cristina Mestre Ferrer
Cristina Mestre Ferrer
B.Sc., M.Sc.
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 about Cristina Mestre Ferrer
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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