The ovary releases an egg which travels through one of the fallopian tubes where fertilization normally happens. Once the egg is fertilized, your baby’s genetic makeup and sex are already determined. The fertilized egg, now called an embryo, starts dividing into many cells and stays about 3 days in the fallopian tube before moving to the uterus where it implants itself in the uterine wall. In three weeks, the embryo forms a ball of different types of cells. After the eighth week of conception until birth, your baby is called a foetus.
The growth and development of your baby in the womb can be divided into distinct 3-month stages called trimesters. We shall look at your baby’s growth on a monthly basis.
Within the first month, the amniotic sac and the placenta have formed for your baby’s protection and nourishment. The face starts to develop with large dark areas for eyes. The mouth, lower jaw and throat have also started forming. No bone is present yet, only areas of cartilage. By week 4, blood cells have formed and circulation is present with a tubular pulsating structure representing the heart. By the end of the first month, your baby is about 1.3cm long.
In the second month, your baby’s face develops further with eyes developing at the dark areas and ears that start as folds of skin developing on the side of the head. Tiny buds appear from which your baby’s arms and legs will develop. Fingers and toes start forming early and can soon be identified. By week 6, your baby’s heart beat can be detected. The nervous system gets more organised with development of the neural tube which later develops into the brain, spinal cord and other neural tissue. Sensory organs have also started to form. The digestive tract starts developing and bone starts replacing cartilage. Your baby is about 2.5cm long by the end of the second month.
By month 3, your baby’s limbs show significant development with well-formed hands, feet, fingers and toes. Fingernails and toenails have started developing. Your baby can now make a fist and open and close the mouth. Teeth have started forming. The external ears have developed further. The reproductive organs are still in the early phases of development and your baby’s sex is difficult to determine on imaging studies. All organs have formed by the end of the third month and will continue to develop in the subsequent months. The liver produces bile and the circulatory and urinary systems are functioning. If your baby has passed through this critical stage of development, the chances of a miscarriage are relatively low. By the end of the third month your baby is about 10cm long.
In this month, your baby has eyelids, eyebrows and eyelashes. Fingers and toes are well defined. Nails have formed. Your baby may yawn, make faces, suck on a thumb and stretch. Genitalia and reproductive organs are fully formed and can be identified on an ultrasound. By the end of month 4, your baby is around 15cm long.
During this month, you will start to feel your baby moving as muscles are developing which need exercise. Hair starts growing on the head and soft fine hair called lanugo covers your baby’s temples, shoulders and back. This is usually shed a week after your baby is born. A whitish coating called vernix caseosa protects your baby’s skin from the amniotic fluid. By the end of this month your baby is about 25 cm long and may weigh 0.2 to 0.4 kg.
During the sixth month, your baby’s skin is reddish, wrinkled and translucent with veins visible. The eyelids start parting. Your baby responds to sound by moving or a change in heart rate. You may feel your baby’s hiccup with jerking movements. By the end of this month, your baby is about 30 cm long and weighs about a kilogram.
By this month your baby responds to different stimuli such as sound, light and pain and is frequently changing position. Body fat reserves develop as your baby matures. The amniotic fluid starts reducing in quantity. At the end of month 7, your baby is about 35 cm long and weighs about 1.5-2 kg. If your baby is born prematurely at this stage, it may survive with intensive care.
During month 8, brain development accelerates and hearing and vision improve. Your baby continues to mature and most of the organ systems are well formed, except the lungs. Your baby moves more and kicks a lot. At the end of this month, your baby is about 45 cm long and weighs approximately 2.2 kg.
In this month, the development of the lungs is nearly complete. Movements are more coordinated, and your baby can blink, turn its head and has a firm grip. Response to stimuli continues to develop. As your baby grows, it does not move as much as the space around it reduces. Your baby then gradually descends and will normally assume a head down position in preparation for birth.