Physical Changes During Pregnancy For The Third Trimester

By Wendy Innes. May 7th 2016

The third trimester of pregnancy is often one of apprehension. The pregnancy is approaching its end, and labor and delivery are close at hand, causing anxiety in many women. Worries about pain, their abilities as a mother and concern over how they'll look after childbirth are just some of the reasons women become apprehensive. Mom may also notice that the fatigue from the first trimester has returned. Here are the physical changes during pregnancy that may occur in the third trimester.

Reproductive Changes

In the third trimester of pregnancy, the uterus now reaches up to the bottom of the rib cage, giving way to the popular pregnancy complaint that the baby is kicking Mom in the ribs. At this point, the baby is typically turned upside down and facing a mother's spine in preparation for birth.

In the last couple of weeks of pregnancy, women may experience something called lightening. This is when the baby starts to move down into the pelvis in preparation for birth. While Mom may not feel anything, she may find that she can suddenly consume more food and breathe a little easier.

Breast Changes

In the third trimester of pregnancy, breasts are working overtime in preparation for feeding the new baby. They will continue to grow and in the last couple of weeks of pregnancy, Mom may notice a yellowish, milky substance, called colostrum, coming from her nipples. This is the baby's first food and it will sustain the baby for a few days after birth until Mom's milk comes in. It is extremely nutrient-dense and calorie-rich, and is essential for keeping the baby healthy. When a mother is ready for breastfeeding, typically three to five days after birth, she may suddenly find herself soaking wet with swollen breasts. This is completely normal, and is nothing to be concerned about.

Cardiovascular Changes

During the third trimester, it is common for the mother's blood pressure to rise slightly due to the increased workload of the cardiovascular system, as the blood volume has reached its peak. It's extremely common for pregnant women to experience problems with swelling, particularly in the lower extremities. This is because the baby is putting pressure on the blood vessels that lead to the lower body, trapping fluid in the legs. To help relieve this, Mom can try compression stockings, laying down with her feet elevated or laying on her left side.

Urinary Tract Changes

During the third trimester a pregnant women may feel the need to urinate frequently and urgently. The reason is that the growing baby puts pressure on the bladder, meaning the bladder can't completely fill before needing to be emptied. When lying down, particularly on her left side she relieves the pressure on the main vein that supplies blood to the kidneys, thereby increasing the efficiency of their function. This is why Mom needs to urinate more at night.

Respiratory Changes

In the third trimester, the uterus has reached the ribcage. Because of this, women often report that they have a hard time taking a deep breath. The rate of breaths increase to keep the levels of carbon dioxide in the blood low. The diameter of the woman's chest may even expand due to the upward pressure. This will all return to normal after birth.

Digestive Changes

By the time the woman reaches the third trimester, she likely can't eat a large meal, but instead eats small meals throughout the day. Heartburn and belching are quite common now as the digestive organs are highly compressed by the growing baby. Mom can rest assured that she should have no problem eating a full meal after the baby is born, even though the uterus will still be enlarged for a few days. Hemorrhoids are also quite common at the end of pregnancy and result from the pressure of the uterus on the rectum.

Skin Changes

It is very common for women to experience itchy skin, especially on their belly, legs and breasts. A good moisturizer can help relieve this itching, typically caused by the stretching of the skin to accommodate Mom's growing shape. During the last trimester, the mother may develop a condition called pruritic urticarial papules and plaques of pregnancy, or PUPPP for short. This rash develops in about 1 in every 150 pregnancies and is characterized by an itchy, bumpy rash that can spread to the extremities. Although it is irritating, it poses no risk to the baby. It is most common in first time mothers or those carrying multiples, and should disappear shortly after birth.

Hormone Changes

Hormone levels will continue to be high in late pregnancy. When it is time for labor to start, the body will begin to produce oxytocin, a hormone that triggers uterine contractions and cervical dilation. Sometimes the mother's body doesn't produce enough oxytocin and it must be supplemented in order to get Mom into a favorable labor pattern. In the hospital, it is called pitocin.

Musculoskeletal Changes

Women may feel increased wobbliness in the third trimester. Loosening joints along with a shifting center of gravity may make it hard for Mom to get around quickly at the end. Backaches are quite common and can mask the early signs of labor. Often labor pain can be felt in the back, but if Mom has had a backache all along, she may not notice until labor is more advanced.

In the third trimester, Mom should be alert for any signs of bleeding or amniotic fluid leaking from the vagina, as well as contractions, extreme back pain that comes in waves, or high fever. Any of these symptoms should be reported to the doctor immediately.

The third trimester marks the end of a rite of passage for a woman's first pregnancy, where she goes from woman to mother. It's nothing to be fearful of, but rather embraced. Once the baby is placed in a mother's arms after delivery, all the discomfort and strange symptoms will be long forgotten.


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