First Trimester of Pregnancy

Weeks 1–6 

Baby’s development 

After the embryo has implanted in the lining of your womb, the foetal brain, lungs, central nervous and intestinal systems start to form. By the end of week six, the embryo measures about 4mm and the heart starts to beat. At this juncture, an ultrasound scan through the vagina can detect the heartbeat and confirm that the pregnancy is in the right location. The foetus is too small to be seen clearly by the abdominal scan at this stage. 

Your symptoms 

You may feel fine and the first clue that you might be pregnant is usually a missed period. Some women complain of breast tenderness or tiredness. You can do a home pregnancy test and consult a doctor for confirmation at about six weeks. Let him know if you are on long-term medication or have any medical conditions. 

Weeks 7–12 

Baby’s development 

The foetus will go through rapid growth. By week 12, most of the major organ systems would have developed and the foetus measures about 6cm from head to the buttock. The following changes are observed: 

  • The head is growing to accommodate the enlarging brain.
  • Eyelids are present in the shape of folds. By the end of week 12, they will meet and fuse, remaining closed until the end of week 24.
  • External sex organs are well differentiated by week 12.
  • Limbs continue to develop and nails appear on the digits. The moving limbs can be “seen” on a scan but movements cannot be felt yet. 

Your symptoms 

Your pregnancy hormones will start to kick in. You may experience morning sickness, breast tenderness and fatigue. 

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