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Zygote
When a sperm has just fertilized an egg it becomes a zygote and this will last for 1 week -
Embryo
The blastocyte forms into a embryop on week 12 -
Fetus
It is a fetus from week 12 on. -
Trimester 1 Weeks 1-4
The embryo forms layers that will develop into organs. The heart now begins to beat, and the spinal column begin to form. -
Trimester 1 weeks 5-8
Finger buds arise and the eyes are more obvious. Toe buds and eyelids will develop during this month, and nerve cells in the brain will connect. -
Trimester 1 weeks 9-12
By the end of 12th week, the fetus is about 2.4 inches long from head to rump. The spinal tail is gone and the face is different. -
Trimester 2 weeks 13-16
the eyelids now cover the eyes, which will not reopen for about three more months. The legs and feet are well developed. -
Trimester 2 weeks 17-20
The fetus now weighs between 10 and 11 ounces, and now covered with fine hair called lanugo. -
Trimester 2 weeks 21-24
By the end of your sixth month, the fetus will weigh nearly two pounds and the head-to-rump length will be over nine inches. -
Trimester 3 weeks 25-28
Most fetuses turn to the head-down position now. Lungs continue to develop. Babies born at this stage usually survive but will require a lot of intensive care. -
Trimester 3 weeks 29-32
The body is more in shape,and the lanugo hairs are almost all gone. The baby can grasp firmly with his or her hands. -
Trimester 3 weeks 33-36
The baby is now due, At the end of 36 weeks, most babies will be about 7.5 pounds with length of nearly 15 inches and a total length of about 21 inches.