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Conception
Conception occurs when a sperm cell from a fertile man swims up through the vagina and into the uterus of a woman and joins with the woman's egg cell as it travels down one of the fallopian tubes from the ovary to the uterus. -
Two Weeks
By the end of the two weeks, the zygote is about the size of a pinhead. The heart, which is no larger than a poppy seed, has begun beating. The egg has attached itself to the lining of the uterus. -
Two Months
The zygote is about 1/4 inch long and has distinct, slightly webbed fingers. Face, eyes, ears, and limbs have developed. Veins are clearly visible. The heart has divided into right and left chambers. *Zygote changes into an embryo at the end of eight weeks -
Three Months
By now the fetus is 1 inch long and is fully formed. He/she has begun swallowing and kicking. All organs and muscles have formed and are beginning to function. -
Four Months
Baby is covered with a layer of thick, downy hair called lanugo. His/her heartbeat can be heard clearly. This is when the mother may feel the baby's first kick. Size: about 3 inches long. -
Five Months
A protective coating called vernix caseosa begins to form on the baby's skin. At this time the baby is about 6 ½-7 inches long and weighs almost 4-5 ounces. -
Six Months
Eyebrows and eyelids are visible. The baby's lungs are filled with amniotic fluid, and he/she has started breathing motions. If the mother talks or sings, the baby can hear. 8-10 inches, about 8-12 ounces. -
Seven Months
At the beginning of the seventh month, the baby weighs about 1 ½ pounds and is about 14-16 inches long. His/her body is well-formed. Fingernails cover the fingertips. -
Eight Months
Baby is gaining about half a pound per week, and layers of fat are piling on. He/she has probably turned head-down in preparation for birth. He/she weighs between 2 1/2 and 3 pounds. -
Nine Months and Birth
Baby is a hefty 5 to 6 pounds and measures between 17 and 18 inches. As he/she becomes more crowded, the mother may feel the baby move around less. During childbirth, the muscles at the top of your uterus press down on the baby's bottom. Your baby's head then presses on your cervix which, along with the release of the hormone oxytocin (see 'How hormones help you give birth', below), brings on contractions.