Your baby is about 6cm long – about the size of a plum – and weighs about 18g. The fetus has almost doubled in size in the past 4 weeks and is now fully formed, with all of the organs, muscles, limbs and bones in place. At this point, your baby fills your whole uterus.
The head is about half the length of the body. The arms appear a more normal length, although the legs are still short. The kidneys are functioning, and the baby is swallowing amniotic fluid and passing urine. They are practising breathing movements and their digestive system is starting to practise too.
The baby is moving around constantly – stretching, yawning and wriggling. The heart is beating strongly and can be heard with a heart monitor.
Some women notice dark patches on their face or neck, called ‘chloasma’. You may also develop a dark line from your belly button down to your pubic area, called the linea nigra. These are both caused by the hormonal changes going on in your body.
Things to remember
Week 12 is when many women start their routine antenatal visits. This can be with your doctor, a midwife or an obstetrician. How often you see them will depend on how the pregnancy is going, as well as your circumstances.
Now is the time to organise diagnostic or screening tests, if you are going to have them. Screening tests that are available to you from 12 weeks include:
- combined first trimester screening test: a combination of a nuchal translucency scan (an ultrasound) and a blood test
- non-invasive prenatal test (NIPT): a reliable but expensive blood test to screen for Down syndrome
- chorionic villus sampling (CVS): a test that diagnoses Down syndrome or other disorders by taking a sample of cells from the placenta
Some women can feel down or anxious when they are expecting a baby. This is very normal, but if the feelings last for more than 2 weeks it’s a good idea to mention them to your doctor or midwife. It’s possible to develop antenatal depression or anxiety when you’re pregnant, especially if you have had a mental health condition in the past. If this happens, it’s important to get help as soon as possible.
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Last reviewed: August 2019