Unborn baby development
How pregnancy begins
Some time after a woman’s period, her body releases an egg. If she has sex around this time, conception — also known as fertilization — may happen.
When fertilization occurs, the baby’s features, including sex, hair and eye color, have already been determined. Did you know that 21 days after conception, your baby’s heart begins to beat?
The timeline below was developed from the medical textbook: Before We Are Born – by Moore and Persaud. Videos are from: The Endowment for Human Development – www.ehd.org
5th week (since conception – approximately the 7th week since the woman’s last period)
The baby’s head takes up about one third of her or his body’s total volume. The beginning stumps of the arms and legs stand out darkly. The baby’s arms develop faster than the baby’s legs do. At this point his or her skeleton has barely begun to form. No bone has yet been formed. Brain waves are detected from about 40 days and have been recorded.
The formation of all the baby’s organs are complete. Everything is now present that will be found in a developed adult. The heart has been beating for more than a month, the stomach produces digestive juices and the kidneys are functioning. Forty muscle sets begin to operate in conjunction with the nervous system. At this stage the cartilage begins to change to real bone cells.
The baby’s features are now becoming more defined. His or her lips open and close, he or she wrinkles his or her forehead, he or she raises her eyebrows, he or she turns her head. The baby’s eyes are covered by eyelids even if they don’t seem to be. Fingernails grow on the hands and feet, the spinal column becomes bony and little outgrowths of breasts appear upon the young chest.
The baby’s body has filled immeasurably. It has begun to crowd its living quarters. Her or his head, neck and spine curve to follow the circular uterine cavity. The baby now occupies all the room in her or his mother’s pelvis. The first thin transparent layer of skin begins to replace the temporary protective membrane. The eyes are still closed and her nose, eyes and lips and ears are shaping up.
The baby’s mother has definitely begun to feel movement by now. If a sound is especially loud, the baby may jump in reaction to it. His or her mother will also feel her hiccups. He or she might sit upright with straightened back and legs crossed in a yoga-like position or her or she could be lounging back with his or her arms folded under her head. The baby may pedal his or her legs, make crawling movements, roll over or turn somersaults.
His or her oil and sweat glands are functioning. The delicate skin is protected from the fetal waters by a special ointment called vernix. She or he opens her or his eyes when the eyelids become unsealed. She or he scans the darkness. She or he may blink if there is a sudden noise. For the last few weeks she or he has virtually all the neurons she or he will ever have in her brain. Variations in her or his heart beat can be recorded. She or he drinks the amniotic fluid and would survive outside the womb if she or he was born early.
The baby is now using the four senses: vision, hearing, taste and touch. The baby recognises his or her mother’s voice. There is still space enough for the baby to straighten up, as he or she puts her hand to her mouth to suck his or her thumb. His or her eyes are open, his or her eyelids are fringed with lashes and the baby often moves his or her eyes as if searching for something to see. The amniotic fluid is reduced by half to allow the baby room to grow. The baby is gaining weight quickly and by the end of the seventh month may weigh 1.8 kgs.
His or her skin is beginning to thicken with a layer of fat stored underneath for insulation and nourishment. Antibodies are building up. He or she absorbs three and a half litres of amniotic fluid per day; the fluid is completely replaced every three hours. His or her taste buds are developed and she seems to have a sweet tooth. She is responding to familiar noises such as his or her mother’s voice and music and her or she will gain 0.9kg this month.
He or she is likely to add only about half a kg now because he or she will get less nourishment from the ageing placenta in the run-up to birth. An essential part of his or her weight gain, about half a kg of it, is laid down as covering fat which will help to keep his or her warm. It will also make her more attractive as his or her body becomes more chubby. His or her face fills out more as his or her cheeks fatten up. He or she will soon take up her position for birth.