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Your 12 Week Fetus

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By week 12 of pregnancy, your baby has already completed the embryonic stage and is now a fetus, which is Latin for "offspring".

All of his organs are fully formed (they just need to get a lot bigger!) and he looks recognizably like a human being.

He has a well-formed face with tooth buds in his mouth. These buds are the beginnings of his baby teeth.

His eyelids will fuse shut and not reopen again until about 28 weeks. He has long, well defined limbs and can even make a fist with his little hands.

Between the ages of 11 and 14 weeks, his liver begins producing its own red blood cells.

The baby’s genitals are completely developed. In recent years, with the invention of 3D colour scanning, it has become possible for experienced medical professionals to accurately identify the baby’s gender from as early as 11 weeks, although their accuracy is better after 12 weeks.

Doctors in the field of obstetrics and gynecology would like to be able to identify gender earlier on so they can avoid tests for X-linked disorders in some mothers-to-be.

In a study of 200 pregnant women, transvaginal scanning with 3D imagery was used to see if researchers could correctly identify the sex of first trimester unborn babies. By using 3D imagery, 150 babies were assigned the correct gender, giving the transvaginal scan an 81.5 percent success rate.

Of the babies that could not be assigned a gender, or were thought to be the opposite gender, it was not the scanning technique that caused the error but was because of the position of the baby.

Sometimes the probe was too far away from the genitals to get a picture, sometimes the legs were closed and sometimes the cord was between the legs.

Researchers would need to have a 100 percent accuracy rate before they could use 3D transvaginal scanning as a routine tool for diagnosing X-linked fetal disorders in the first trimester. But even with less accuracy, they believe the technique could be used so that in future, women have the option to defer invasive X-linked fetal testing if they wish.

Your Baby's Behavior

New 3D scanning also gives us an insight into fetal behavior. For the first time ever, it allows doctors and parents-to-be to see what babies get up to in the womb.

Babies as young as 12 weeks have been seen stretching, kicking, leaping and mimicking upright walking movements in the uterus. If a newborn baby is held upright at birth, he will attempt to move forward, but until recently doctors did not know this reflex began so early in gestation.

Your baby of 12 weeks can also suck his thumb.

What About You?

At 12 weeks pregnant, most women find their morning sickness is starting to subside. You might also find your clothing starts to get a little bit tight, particularly if you have already had a child in the past. If you don’t have any maternity clothing in your closet, now is the time to go shopping!

If this is your first pregnancy, you probably won’t feel the baby move until you are about 20 weeks gestation, but subsequent pregnancies can be felt much earlier.

The American Pregnancy Association say "quickening" (being aware of baby’s movements) can occur as early as 13 weeks in women who already have children. However, some women report feeling their baby even earlier.

Women with a large family are more likely to feel movement very early because their womb has been stretched repeatedly and so it is easier to feel fetal movement. In an online survey, 20 percent of women stated that they felt their baby move at 11 to 12 weeks gestation.

You might need to schedule a dental appointment at this time. Due to hormone changes your gums may become thinner and prone to bleeding.

The American Pregnancy Association recommend brushing your teeth twice a day and rinsing them in salt water. They also recommend at least one visit to a dentist during your pregnancy.

If you live in the UK, dental care is free to all pregnant women and mothers of infants up to the age of one year.

This will also be the time when you can tell all your friends and relatives your good news (if you haven’t already) because the risk of miscarriage has reduced dramatically.


Fetal Development, Medline Plus. Web. 19 April 2012. http://www.nlm.nih.gov/medlineplus/ency/article/002398.htm

The use of three-dimensional ultrasound for fetal gender determination in the first trimester, British Journal of Radiology (2003) 76, 448-451. Full Text: http://bjr.birjournals.org/content/76/907/448.full

Scans Uncover Secrets of the Womb, BBC News. Web. 19 April 2012. http://news.bbc.co.uk/1/hi/health/3846525.stm

Medhelp Quickening Survey, Web. 19 April 2012. http://www.medhelp.org/posts/Maternal--Child/When-did-you-first-feel-quickening-fluttering/show/969848

First Fetal Movement: Quickening, American Pregnancy Association. Web. 19 April 2012. http://www.americanpregnancy.org/duringpregnancy/firstfetalmovement.htm

12 Weeks Pregnant, BabyCentre. Web. 19 April 2012. http://www.babycentre.co.uk/stages/0112

Joanna is a freelance health writer for The Mother magazine and Suite 101 with a column on infertility, http://infertility.suite101.com/ She is the mother of five children and practices natural childbirth, delayed cord clamping, full term breastfeeding and organic food diet.

Reviewed April 20, 2012
by Michele Blacksberg RN
Edited by Jody Smith

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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.



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