Physiological changes in pregnancy

Respiratory system

The respiratory rate rises by about 20% to offset the increased maternal and infant oxygen consumption.







Cardiovascular system

The heart increases in size and moves up and to the left through the growth of the uterus, which raises the diaphragm.

Blood volume increases by about 30% and the heart rate increases by about 15 beats per minute. Due to the increased blood volume, a hemodilution occurs (that is, the blood is thinner) and a physiological anemia may appear which can be improved with the proper diet or with the contribution ofsome food supplement.

Blood pressure gradually decreases until weeks 16 and 20, and then begins to rise to figures close to those before pregnancy. The so-called supine hypotension syndrome can appear which can arise when the abdomen is being compressed upwards by compression of the vena cava and is usually recovered when placed lying on the left side.

Also, the pressure of the femoral vein through the womb may hinder the venous return of the legs, which may facilitate the appearance of varicose veins and edema (swollen legs). To improve and reduce discomfort it is recommended to raise your legs and take cold showers.

Gastrointestinal system

Nausea and vomiting usually occur, especially in the first trimester and early in the morning; it is recommended to avoid foods high in fat and with strong odors, as well as eating early in the morning something solid, avoiding liquids.

Sometimes the sense of taste is also altered and the sense of smell is usually more pronounced. There may be an increase in saliva or gingivitis (inflammation of the gums).

As the pregnancy progresses and the uterus grows, it displaces the abdominal organs, such as the stomach, and facilitates the ebb of gastric secretions, and this is when the burning sensation (pirosis) appears. Stomach volume is reduced and you work slowly, which is why it is recommended to eat in small quantities but often.

Stomach volume slows down and works slower, so the pregnant woman should make fewer meals so as not to experience excessive fullness after ingestion. As the uterus also compresses the bowels, these slow down their normal functioning and abdominal distention and constipation may occur. Another factor that, like the difficulty of venous return, can be the presence of hemorrhoids.

Changes in the breasts

The breasts are beginning to prepare for breastfeeding, they may grow and become more sensitive to the touch. The nipples and areola may turn darker due to the increased pigmentation. Montgomery tubers - glands that secrete secretions may appear to keep the nipple hydrated and lubricated. And during pregnancy, colostrum can be secreted - initial, thick milk and yellowish in appearance.




Hormonal changes

The placenta acts as an endocrine gland during pregnancy. She is responsible for maintaining the pregnancy, the growth of the uterus and the multiple changes during pregnancy. At the endocrine level, the thyroid gland, the pituitary gland, the adrenal glands and the pancreas increase their functions and their hormonal formations, adjusting the woman's needs.






Abdominal changes


During the second trimester, the abdomen begins to grow to the end of pregnancy. In the middle of pregnancy (week 20) ​​the uterus is approximately at the height of the navel. Pain in the abdomen or back may be felt due to the stretching of the muscles and ligaments due to the growth of the uterus.

Urinary changes

Due to compression of the uterus into the urinary tract, the bladder volume is diminished and it is often necessary to urinate, although the amount may be smaller. An increase in blood volume can lead to an increase in the amount of urine that often affects during the night (nicturia).

Small involuntary outflow of urine may occur with sneezing or laughing also due to compression of the uterus to the pelvic floor muscles.



Musculoskeletal changes

There is a relocation of the curvature of the spine to maintain the balance that results in a change in posture with lumbar hyperlordosis.

The laxity of the ligaments is increased due to the increase in the relaxin hormone that prepares the pelvis for birth, and increased mobility.

Changes in the skin


  • Stretch marks: They usually appear in the second half of pregnancy, especially on the abdomen and breasts, and are caused by stretching of the skin.
  • Hyperpigmentation of the navel area (alba line), nipples and face (chloasma). Their cause is hormonal changes, and they usually disappear after pregnancy.
  • Increased surface circulation due to increased estrogen may result in spider veins and reddening of the palms.