Pregnancy week by week will lead to an exciting new fetal development. The 40 weeks of pregnancy are split into three trimesters or stages.
Fetal development actual begins two weeks prior to a woman's pregnancy. It's not until weeks three and four of a woman's first trimester that the egg is fertilized and implants in the uterus. This is when a home pregnancy test will be able to detect a pregnancy. In the fifth week, a baby's spinal cord, heart, brain and other organs begin to form. During week seven, the baby's head will develop and by the next week the baby's limbs will begin to move. Although it's not until halfway through the pregnancy that you'll feel this. For the rest of the first trimester, the baby will continue to grow rapidly.
The second trimester begins at week 13, shortly before a health care provider will be able to determine the baby's sex. Weeks 15 and 16 are when the baby's skeleton develops bones and the baby begins to move its facial muscles. By week 18, the baby will begin to hear. And at the halfway mark of 20 weeks, you'll be able to feel the baby moving. The rest of the second trimester is accompanied by the development of hair, fingernails and an increased exploration.
The third trimester is one of great discomfort for the woman as the baby grows rapidly and her body prepares for delivery. During the first week of the last trimester, the baby will open its eyes. During the second week, the baby's bones will become fully developed. Sexual development continues and the baby will practice breathing and detect light for the first time. The baby will then begin to prepare for delivery by gaining weight and moving into a head-down position.