If you have experienced the miracle of birth, you may also have wondered just what goes on inside a woman's body during pregnancy. From conception to birth typically takes nine months; plenty of time for organs and bones to develop. Birth may be a miracle, but the actual creation of that tiny person is no less dazzling.
Conception
The human body is, in part, a giant collection of cells. Cells carry your DNA, the very "blueprint" of your particular biochemical structure. According to the Blue Ridge OB/GYN Associates website, when sperm and egg unite, they exchange parts of their DNA to make the new individual. Cell division begins to occur, with one cell making two, two making four, and so on. The sex of the developing child is determined at this time, although it will take many weeks to confirm.
Implantation
Blue Ridge OB/GYN Associates also states that after about a week, this bundle of cells, or zygote, implants itself in the uterus. The uterus is lined by the endometrium, a layer of blood cells and tissue that thickens during a woman's cycle, states the American Congress of Obstetricians and Gynecologists website. If an egg is fertilized and implanted in the endometrium, it will use the nutrients to grow. If no zygote is implanted, a woman sheds this lining during menstruation.
Weeks One to Four
During this time, the bundle of cells is called an embryo. This stage is critical, as the eyes and ears are developing. The head, mouth and legs are also growing, while the heart and lungs are starting to form. At the end of week four, 4parents.gov states that the embryo should be approximately 1 inch long.
Weeks Five to Nine
According to 4parents.gov, during this time period all organs should be finishing development. Blue Ridge OB/GYN Associates also says that at the beginning of the sixth week, a yolk sac should be seen around the embryo. At the end of the sixth week, you may be able to detect some heart activity as well as the fetal pole, or "top" versus the "bottom," of the embryo. The seventh week should see stronger cardiac activity and a definite fetal pole. Brain waves can be detected and recorded. The jaw is also forming, replete with teeth buds in the gums, states 4parents.gov. At the end of nine weeks, your developing baby can be called a fetus.
Weeks Nine to 13
At the end of week 12, the fetus is approximately 3 1/2 inches long and weighs 1 1/2 ounces, states the Blue Ridge OB/GYN Associates website. The placenta is typically formed, and is now supplying the fetus with oxygen via the mother's blood. According to 4parents.gov, fingerprints have formed in the skin, as have fingers, toes and soft nails. The doctor's stethoscope can pick up a heartbeat, and the fetus can move its head and make a fist.
Second Trimester
Hopefully your morning sickness has abated, and you may now feel the baby's movements as flutterings in your body, says the Blue Ridge OB/GYN Associates website. The fetus can pick up sounds from outside, according to 4parents.gov, and the baby grows rapidly. It can move and suck its thumb, and your doctor may be able to determine its gender.
Third Trimester
During weeks 28 to 40, the baby is responsive to touch, light and sound. 4parents.gov says that all five senses are active. The eyes can open, and the baby may have subcutaneous, or under the skin, fat as well as hair development. The baby can experience the hiccups, and you may experience the fetus kicking and moving around. Rapid growth as well as brain development is happening during these weeks, and according to 4parents.gov, the heart is pumping approximately 250 gallons of blood per day. By week 36, if the baby is born prematurely, it has a good chance of surviving, states the website; you are almost at full term.
