The third trimester begins at the 28th week of pregnancy and lasts until birth. This usually is a time of excitement and anticipation of the baby’s arrival. Like many women during late pregnancy, you may be tired of being pregnant, thinking about when labor will start and how your delivery will go. At term, it will weigh about a little over one kilogram, and will have stretched to hold your baby, the placenta and about a liter of amniotic fluid. Nearly all of the physical symptoms of late pregnancy arise from this increase in the size of the uterus.
Shortness of Breath
If you’re like many women in late pregnancy, you may be experiencing some amount of breathlessness. This is because your diaphragm–the broad, flat muscle that lies under your lungs–is being pushed up out of its normal place by the expanding uterus. The diaphragm rises about 4 centimeters from its usual position during pregnancy.
At the same time, though, the hormone progesterone acts on the respiratory center in the brain, causing you to breathe more deeply. As a result, although your total lung capacity is decreased, the volume of air you are taking in with each breath is actually increased during pregnancy. So, despite your own discomfort, the baby’s need for oxygen and blood are being taken care of.
The increased hormones of pregnancy tend to cause the connective tissue in your body to soften and loosen up. One result is that the joints between the bones of your pelvis become more relaxed. The greater flexibility of these bones makes it easier for the baby to pass through them during birth. Unfortunately, it can also have the added effect of producing hip pain. Hip pain in late pregnancy usually occurs on one side. The changes in your posture, along with lower back pain, that result from the heavier uterus can add to your discomfort.
Pain, tingling or numbness running down the buttock, hip and thigh is called sciatica. It can be caused by the pressure of the pregnant uterus on the sciatic nerve. Two sciatic nerves run from your lower back down your legs to your feet.
Some women occasionally feel a sharp, stabbing pain inside the vagina during late pregnancy. This is probably linked to the cervix starting to dilate, which can happen weeks, days or hours before labor begins. It is usually nothing to be concerned about, but tell your doctor if it causes a great deal of discomfort. Any severe pain in the lower abdomen should be reported to your doctor right away.