SECOND TRIMESTER

This is the period between 13^th to 24^th week of pregnancy. Detailed below are the normal changes that take place in the growing baby during this stage.

THIRTEENTH WEEK

At 13 wks: 7½ cms in length about 30 gms in weight. The uterus also grows in size and it is ONLY NOW that your obstetrician can feel it in the lower abdomen. The uterus measures about 10.2 centimeters and the amniotic sac contains about 100 ml of amniotic fluid. The growing baby is suspended in this fluid, protected it from injuries. The changes that take place during this period include:

• A more rounded head and a fully formed neck.
• Free movement of the head on the trunk.
• Complete development of the face with mouth, nose and eyes.
• Completion of the development of the external ear.
• Fully formed internal organs. The lungs, liver, kidney and the intestines however continue to grow and mature.
• Further development of external genitals. At this stage the sex of the baby is obvious and may be detected through an ultrasound.
• Increased movement of the baby, but not strong enough for the mother to feel them.

Although all the organs are formed by the end of the thirteenth week, they are yet to mature and carry out their normal functions. At this stage of pregnancy, only a few disease causing agents such as those for syphilis, toxoplasmosis or certain viral infections can harm the baby and cause abnormal growth of a particular organ.

SIXTEENTH WEEK

At 16 wks: 16 cms in length about 135 gms weight. Body changes during this period include:

• Completion of formation of the limbs and joints, which begin to move.
• Very active movements of the body, which are not yet strong enough for the mother to feel.
• Further growth of the body so that the head is not as large, as earlier, compared to the body.
• External sexual organs continue to develop and the sex of the baby can be easily recognized.
• Development of hair including eyebrows and eyelashes.

TWENTIETH WEEK

During this period the baby continues to grow very rapidly and is about 25¹/₂ cms and weighs about 340 gms. The muscles grow rapidly and therefore the limbs move actively. By this time a mother is able to feel the baby moving. The total volume of the amniotic fluid increases so that the baby is able to move and turn very easily.

TWENTY-FOURTH WEEK

At 24 wks the baby measures about 33 cms and weighs about 570 gms. During this period the baby continues to grow and the vital organs continue to mature. If the baby is born at this stage, it can survive for a short time. It cannot live longer as the lungs are not yet fully developed and mature. There are however reported cases of babies surviving at this stage after specialized care in the intensive premature baby care unit.