Pregnancy can be divided into three terms (or trimesters), each lasting about 14 weeks/3 months. We will now talk about the developmental stages of pregnancy until birth.
In the first after of conception, the fertilized egg will be travelling to the uterus, where implantation will occur. In the third week, the embryo will grow rapidly, with the division of cells of the egg. The foundation will be laid for development of the baby’s brain, spinal cord, heart and gastrointestinal tract.
In the fourth and fifth stages of pregnancy, the embryo will show arm and leg buds, which will eventually form the limbs. These are not yet distinctly visible.
Week 6 sees the formation of the jaw, nose, lungs and palate, following the rudimentary eyes and ears. At this stage, your doctor can check the heartbeat with ultrasound equipment. Although complex changes are taking place and the basic body structure is being formed, the embryo is still only about half an inch long.
At 7 weeks, the essential organs have already started to form but the embryo weighs no more than a headache pill. The facial muscles and the eyelids and tongue have started to grow. The trunk which has been in a curved position now begins to straighten slowly.
In the 8th week, the ears continue formation, both inside and out. At this stage, the embryo is a miniature version of an adult. The bones grow on, with the calcium absorbed through the mother. The facial features become distinct. This is the stage where a so called ‘embryo’ is called a ‘foetus’. It’s still only one inch long.
In the weeks 9 to 13, it grows in length to about 3 inches. Although genitalia have formed, the ultrasound cannot pick it up clearly. The eyelids are tightly shut until the 28th week of pregnancy. The head is one half of the foetus in size.
Weeks 14 to 16 show development of hair on the head. Fingerprints have now formed on the tiny, clenched fingers. Meconium forms in the intestinal tract, the precursor to baby’s bowel movement. Mum will now be able to feel the movements of her baby.
During weeks 17 to 20, the baby will be actively moving. The heartbeat is now audible by a stethoscope.
The entire body is covered with lanugo (soft hairs) from weeks 21 to 23. The skin becomes less transparent and fat develops. Formation of the liver and pancreas will be nearing completion.
Weeks 24 to 26 is considered the viable earliest time timing for birth, should it be medically necessary. The lungs are growing to prepare for the life ahead and the nervous system also grows rapidly.
Weeks 27 to 32 see the foetus really putting on weight, storing fat. It becomes about 16 inches in length.
During the 33 week onwards, the foetus will position itself upside down so as to prepare for birth. The lanugo is slowly disappearing from the skin. The weight reaches over 5 lbs, in a healthy baby. After 37 weeks have been completed, the baby is ready to come out. |
