Fetal Development
Conception
At the time of conception, which generally occurs in the fallopian tube, every part of the baby’s make up is determined: his or her hair color, sex, facial features, and eye color. The zygote, as the baby is called, spends the next few days traveling down the fallopian tube to the uterus where, on day 6 or so, (s)he implants in the uterus. As the blastocyst takes up residence in her mother’s uterus, (s)he gathers nourishment from the mother’s bloodstream.
Growth
The embryo quickly begins to develop a nutritional system and to differentiate body parts and organs. Within her/his first four weeks the embryo’s heart begins to beat, the brain and nervous system are established, and arms, legs, mouth, eyes, and ears begin to appear.
Week 6
By the sixth week brain waves are noticeable and the brain is beginning to control the baby’s movements. The little embryo’s liver is now producing her blood cells and five fingers can be seen on each hand.
Week 8
In another two weeks the embryo is now called a fetus (Latin for “young one” or “offspring”). The Fetus now has everything found in a healthy adult and (s)he responds to touch. By the end of the 12th week the fetus is “breathing”*, sleeping, waking, and exercising.
Weeks 12-24 (2nd trimester)
During the second trimester of pregnancy the fetus begins to develop hair. By the end of the fourth month the sex of the baby can be determined through ultrasound. All of the baby’s muscles and bones are being strengthened and (s)he is able to feel pain. The fetus is 8-10 inches long and weighs about a half a pound. Movement is able to be felt by the mother.
Month 7
By the baby’s 7th month (s)he is using four senses: vision, hearing, taste, and touch. (S)he is also able to recognize his mother’s voice.
Delivery time
The average pregnancy lasts about 9 months from the time of conception, or approximately 40 weeks from the fist day of the mother’s last period. By this time the baby usually weighs between 6 to 9 pounds and his heart is pumping 250 gallons of blood per day.
*At this stage of development, the fetus “breathes” the amniotic fluid which exercises and lubricates the baby’s lungs