A woman's pregnancy lasts approximately 40 weeks, according to WomensHealth.gov. The duration of pregnancy is divided into three sections, called trimesters. The first trimester covers weeks 1 through 12, the second trimester weeks 13 through 28 and the third trimester weeks 29 through 40. Each trimester brings with it a distinct set of pregnancy symptoms.
First Trimester
The female body experiences a number of hormonal changes in the first trimester. Nearly every organ in the body is in some way affected by pregnancy, says the WomensHealth.gov website. Upon conception, the female period ceases and the body may experience tiredness, upset stomach with occasional morning sickness, swollen breasts, increased hunger cravings, headaches, heartburn, a need to urinate more often, mood swings, constipation and possible weight loss or gain. Many of these symptoms will dissipate as the pregnancy progresses. It is possible for the female body not to experience any of these symptoms, or just a few. At this point, the baby's brain and spinal cord have formed, and the heart is being developed. By the end of the first trimester, arms and legs are fully formed and the sex of the baby has been determined but is likely not detectable yet through an ultrasound.
Second Trimester
During the second trimester, many of the characteristics of the first trimester may fade but new symptoms can arise, the most noticeable being the increase in size of the mother's abdomen. Other symptoms unique to the second trimester include body aches, especially in the back, thighs and groin area, potential stretch marks on the abdomen, thighs, buttocks and breasts, and darker skin around the cheeks, forehead, nose and upper lip. The area around the nipples may also begin to darken. Some women experience carpal tunnel syndrome -- numb or tingling hands -- and itching in the palms and on the soles of the feet. The ankles, face and hands may begin to swell. According to MayoClinic.com, some women experience Braxton Hicks contractions. These are not to be confused with the contractions of birth, but are simply a reflex by the uterus to build strength for the actual birth. The baby's muscles and bones continue to develop, along with nearly translucent skin. By the end of the second trimester, foot and fingerprints are formed and hair begins to grow.
Third Trimester
Some symptoms, such as achy or swollen joints, from the second trimester continue in the third trimester. In addition, some women have reported trouble breathing and an even greater frequency of having to use the restroom, according to WomensHealth.gov. This can be attributed to the fact that the baby is growing and requires more room in the abdomen, therefore placing pressure on abdominal organs. Third trimester symptoms also include hemorrhoids, leaky breasts, a protruding belly button, trouble sleeping and contractions. It's not all negative, though, as many women report increased energy and feelings of well-being during this trimester. As birth nears, the cervix thins and softens to help prop open the vaginal birth canal. By now, the baby's bones are completely formed. The eyes begin to open and the baby starts to put on more and more weight by storing nutrients. By the end of the third trimester, the baby's organs are able to function on their own and it is ready to be born.
