Effects of Pregnancy on Body Systems

Effects of Pregnancy on Body Systems

These are some changes you may notice during your pregnancy.  If you have any questions about any changes check with your midwife.


Integumentary System: The skin in influenced by the increased hormones of pregnancy.  Some pregnant women perspire more than usual and their odor can change. Oiliness of the skin increases due to pregnancy and the hair can appear to grow faster. The skin starts to stretch and stretch marks may appear on the enlarging breasts, abdomen and thighs.  In some women increased pigmentation of the skin occurs.  You may find a dark line called lina negra from above the naval down to the boarder of the pubic hair.  The areola and vulva may darken as well.  Facial discoloration my appear as tanned, bronzed, or freckled blotches called cholasma.


Skeletal System: The absorption of calcium increases in the small intestines during early pregnancy.  Calcium absorption has doubled by the beginning of the third trimester and remains elevated during postpartum. It is important to take plenty of calcium during this time. Maternal bones utilize what the fetus does not.  Bone content can diminish during breastfeeding if calcium and phosphorus intake is inadequate.  A change in the woman’s gait is often noticeable as pregnancy advances.  The enlarge uterus causes the balance of the body to be altered; the shoulders are thrown back and the lumbar curve is increased, which along with relaxation of the pelvic joints and ligaments during the later weeks of pregnancy, may lead to backaches.


Muscular System: During pregnancy the muscles, tendons and ligaments are influenced to relax by the action of progesterone and relaxin.  This allows maximum opening of the pelvic bones during birth.  It is much easier to pull muscles or cause damage to the muscles, tendons and ligaments during pregnancy.  Women should be conscious of this tendency when exercising, or engaging in strenuous activity.


The senses: Visual alterations during pregnancy vary widely from woman to woman due to hormonal and fluid balance changes.  Tear production decreases which can lead to nearsightedness and can reduce corneal sensitivity.  These changes reverse themselves after the birth.  Taste is generally dulled during pregnancy and the sense of smell is usually heightened.  Touch can be heightened as well and some parts of the body may become extremely sensitive.


Endocrine System: The elevated estrogen of pregnancy causes Thyroid Binding Globulin levels to double at about 12 weeks and return to normal around 6 weeks postpartum.  The concentration of hormones secreted from the parathyroid gland and the size of the glands increase in order to meet fetal calcium requirements.  The pituitary gland enlarges during pregnancy and returns to normal size after birth.  Estrogen is secreted by the ovaries and adrenal cortex levels increase 1000-fold in pregnancy, which influences the growth and function of the uterus and breast.  External genital changes and increases the pliability of connective tissue.  It decreases gastric secretions, increases skin pigmentation as well as sodium and water retention and increases the clotting ability of fibrinogen.  I may also influence the emotional mood swings of pregnancy.  Progesterone production increases ten-fold during pregnancy.  It is responsible for the development of the decidual cells in the endometrium, decreases the contractibility of the pregnant uterus and helps develop the lobes of the alveolar system of the breast.  It influences the hypothalamus to cause extensive fat storage in the mother, stimulates the respiratory center, increases the basal body temperature, increases the amount of sodium excreted by the kidneys, relaxes smooth muscle, and decreases gastrointestinal motality as well as the muscle tone of the bladder and uterus.  Prostaglandins are produced by the mother’s body as well as the fetus and placenta.  They help to soften the cervix and prime the body for labor.  Prolactin is produced by the fetal and maternal pituitary glands and by the uterus.  It helps to sustain milk production and regulate milk composition during lactation, and enhances the mother’s ability to attach emotionally to her newborn.  Oxytocin is produced by the hypothalamus and sent to the pituitary gland for release.  It stimulates uterine contractions as well as milk let down and ejection.  Distention of the cervix and yoni stimulates the release of oxytocin and prostaglandins.


Circulatory/cardiovascular Systems: During pregnancy the blood volume and cardiac output both increase.  The number if endometrial blood vessels is greatly increased as the uterus enlarges and the placenta becomes a highly vascular structure. Cardiac output (how much blood the heart pumps) rises during the first few weeks and in 30-45% above non pregnant levels by the 20th week where it remains until term.  The enlarging uterus causes the diaphragm to rise.  This displaces the heart to the left and upward.  In late pregnancy the uterus partially impairs venous return from the inferior vena cava, accounting for the lower cardiac output that can be measured when the woman lies on her back.  Cardiac demands increase significantly during labor and delivery.  Pain increases sympathetic muscle tone, and uterine contractions induce wide swings in systemic venous return.  Evidence of these changes include full and bounding pulses or, in some women, and overall rise in blood pressure.  It is common for the mother’s pulse rate to rise 10 to 15 points and pregnancy advances.  Some shortness of breath and edema may occur.


Immune system: Once the pregnancy is established, placental and hormonal factors combine to prevent the maternal system from rejecting the fetus.  Although there may be changes in the maternal immune system, women have no predisposition to infectious disease during pregnancy, with the exception of a few viral illnesses.


Respiratory System: During pregnancy, oxygen consumption rises 15 to 20%.  Roughly one-third of this increase is necessary for the metabolism of the fetus and placenta.  The remainder is used to support the increased maternal metabolism.  Breathlessness is a normal finding in most pregnant women.  This may be due to the combination of the lungs’ slight displacement upwards as the growing uterus encroaches on the thorax and restricts free movement of the diaphragm, and the deeper respirations necessary to ensure increased oxygen consumption.  In comparison to the heart, pregnancy puts little stress on the respiratory system.


Digestive System: In increase in dental caries has been traced to elevated levels of acidophilic organisms in the mouth due to the hormones of pregnancy.  Gum tissue may become softer and bleed more easily which is partially mediated by hormonal changes but also indicates the need for more vitamin C and bioflavinoids.  Most women experience nausea and vomiting in early pregnancy due to the sudden increase in hormones in conjunction with hypoglycemia.  Food cravings and sensitivities to smell are also common and may aggravate gastrointestinal discomfort.  As pregnancy advances, the intestines are displaced to either side of and behind the uterus.  The stomach is displaced upwards to the diaphragm,  Heartburn may occur because the sphincter between the stomach and esophagus is relaxed by the hormones of pregnancy, causing stomach acids to more easily backwash into the lower esophagus.  Gastric emptying time and intestinal motility are decreased, which may cause increased bloating and constipation in some women.



Urinary System: The ureters are liable to be compressed by the uterus as it rises out of the pelvis.  This, in combination with the increased hormones which cause laxity of all the muscles, reduces peristalsis in the ureters.  Stasis of urine can occur as it gets caught in bends or dialated areas which may develop in the ureters causing pregnant women to be more susceptible to the growth of urinary tract bacteria.  Frequency of urination is common during pregnancy, beginning as early as the sixth week.  The uterus is still within the pelvic cavity and becomes slightly more antiflexed with the weight of the pregnancy.  This produces pressure on the bladder, simultaneously stretching the bladder base, thus stimulating the urge to urinate.  In late pregnancy the uterus again presses on the bladder.


Effects of Pregnancy on Body Systems