It is natural for a pregnant woman to wonder how the baby inside her is developing. Pregnancy is filled with all kinds of marvels, and thanks to modern science and technology, doctors have a fairly accurate idea of what goes on in the womb before birth. This allows expectant parents to know more about the stages of their unborn baby's prenatal development and the factors that can affect it.
Pregnancy and Smoking
Smoking makes it more difficult to conceive and exposes the fetus to toxins in the tobacco smoke. A pregnant woman who smokes will have less oxygen in her blood, which means that her baby will be getting less oxygen. Fetal heart rate rises as the baby tries to get more of the oxygen it needs. The Centers for Disease Control and Prevention warns that infants born to women who smoke are at greater risk of being premature, weigh less at birth and have poor lung function. Babies born to smokers are also at greater risk of suffering asthma, bronchitis and frequent inner ear infections throughout early childhood.
Rubella
Another threat to the health of an unborn baby is rubella, a contagious viral illness that can cause stillbirth, miscarriage or serious birth defects. Although in most cases the symptoms of rubella are mild, if a pregnant woman becomes infected during the first trimester, the infection usually spreads to the fetus. Common birth defects caused by rubella include heart damage, blindness, deafness and mental retardation. While there is no treatment, immunization can prevent the disease. According to a fact sheet published by the Directors of Health Promotion and Education, a Conference that supports state public health programs nationwide, women must receive the vaccine before they become pregnant in order to be immune to the virus.
First Trimester
According to the Mayo Clinic, fetal development occurs rapidly during the first trimester of pregnancy. By the end of the fifth week of pregnancy, a baby's heart, circulatory system, brain, spinal cord and other organs have begun to form. In fact, the heart begins beating about 22 days after conception. Just 10 weeks after conception, the head has developed and movement begins. Eleven weeks into the pregnancy, the embryo is now described as a fetus.
Second Trimester
By the 13th week of pregnancy, all of a baby's major organs have formed and are functioning, even though the fetus is no larger than an adult fist. After 20 weeks, the fetus is passing about three tablespoons of urine each day from the amniotic fluid he swallows. During the second trimester, red blood cells form in the baby's spleen, bones are developing and the baby begins to hear. At the end of the second trimester, a baby has fingernails and is growing hair on his head. He is forming fingerprints and footprints, and should weigh about 2 lbs.
Third Trimester
Although a baby's bones are fully developed by the 29th week of pregnancy, they are soft and pliable. Now is when the baby begins to store calcium, iron and phosphorous. At 32 weeks, the body of a fetus is sensitive to touch and she can feel pain. Even though the baby's lungs are not yet fully formed, she begins to practice breathing.
Final Weeks
During the final weeks of pregnancy, the fetus gains about 1/2 ounce of fat each day. After 37 weeks, a baby is considered to be full term because his organs are ready to function on their own. Throughout these last weeks of pregnancy, the placenta continues to supply the baby with antibodies to help fight infection. These antibodies will be present in the baby until about six months after birth.
