Dan's Papers - June 22, 2007 - Inspirations by Emily J. Weitz

Two weeks ago, I sat with my sister at a health food restaurant in Soho and dined on salads in the afternoon sunshine. When we finished, she leaned back in her seat and rested her hands on her giant, bulging belly. The belly was not a product of her copious appetite, but rather, her pregnancy.

Perhaps the most remarkable part to me is not that this child was conceived or that he will someday grow up to be a man. The thing that absolutely blows me away is the fact that since he was conceived, his cells have been multiplying and changing, and he will continue to develop, albeit at a decreasing rate, for the rest of his life. How did this tiny being develop from a zygote into a baby?

During the first three weeks of pregnancy, the fertilization and implantation processes are taking place. This means that the sperm and egg meet in the fallopian tube, form a zygote and make the journey towards the uterus. The zygote has 46 chromosomes - 23 from the mother and 23 from the father. These 46 chromosomes contain genetic material that will determine features such as hair and eye color, height and facial features.

The zygote travels to the uterus, subdividing the whole way. By the third week, the zygote consists of about 500 cells and the placenta will begin to form.

Week four begins the embryonic period. During this time, the baby's brain, spinal cord, heart and other organs begin to form. By the fifth week, the baby's heart will begin to beat. By this time, the baby is 1/17 of an inch long - the size of a pencil point. An ultrasound may be able to detect the baby's heartbeat.

During weeks six through nine, facial features will begin to form, along with digestive and respiratory systems. The umbilical cord, which carries the nutrients to the baby from the mother, will become visible. Fingers and toes will begin to form and by week nine, hair follicles begin to form.

Week ten is when the neurons begin to multiply rapidly. The baby's brain will produce almost 250,000 new neurons per minute.

By week eleven, the gender may become apparent, as the external sex organs develop. At this time, the baby is officially considered a fetus. In week twelve the fetus will begin to develop fingernails and toenails.

Week thirteen marks the beginning of the second trimester. The baby is able to flex and kick. Tiny ribs may form and the eyes are developing behind lids that are sealed shut. In the next few weeks, reproductive glands and skin will begin to form. Bones and marrow continue to develop. Eyes and ears are almost completely developed. The fetus is able to make facial expressions and make a fist. The eyes become sensitive to light. By week nineteen, the baby will be able to hear.

Week twenty marks the halfway point in your pregnancy. The fetus weighs a little over half a pound and is about six inches long. By now, you will probably be able to feel the baby's movements. In weeks 24-27, the baby can begin exploring the uterus. The hands and eyes are fully developed. Twenty-seven weeks marks the end of the second trimester. The baby's lungs, liver and immune system are continuing to develop, but if the baby were born at this time, he or she would have an 85% chance of survival.

Week 28 begins the third trimester. At this point, the baby's eyes may open and close. The baby sleeps for twenty to thirty minutes at a time. By week 29 and 30, the baby is gaining weight quickly and its movements are so forceful that you will really feel the kicking. By week 32, the baby is between fifteen and seventeen inches long and about four pounds. A baby born in this week has excellent chances for survival. In week 33, the baby's pupils can constrict and dilate and detect light. The baby is gaining half a pound with each passing week and the lungs are almost completely developed.

In weeks 35 and 36, the baby continues packing on pounds and storing fat all over the body. The baby prepares for delivery by moving into the head down position.

By the end of week 37, the baby is considered full-term. In weeks 38 through 40, brain development continues and the placenta continues supplying the baby with antibodies, which will help protect the infant from infection. Week 40 will bring the due date, though only about 5% of women actually deliver on their due date.