Physiological changes during pregnancy
Pregnancy brings extensive physiological changes across multiple body systems. These adaptations are essential to support fetal development, maternal health, and the demands of labor and delivery. Most changes are regulated by hormones such as estrogen, progesterone, human chorionic gonadotropin (hCG), and prolactin. Below is a system-wise explanation of these changes.
1– Cardiovascular Changes
2– Respiratory Changes
3– Renal and Urinary System Changes
4– Gastrointestinal Changes
5– Endocrine and Metabolic Changes
6– Hematologic Changes
7– Musculoskeletal and Postural Changes
8– Skin and Pigmentation Changes
9– Breast and Reproductive System Changes
Cardiac output increases by up to 50% due to elevated heart rate and stroke volume. Blood volume expands by 30–50% leading to physiological anemia. Systemic vascular resistance decreases, often lowering blood pressure in early pregnancy. A systolic murmur may be heard, and there is increased risk of varicose veins and edema due to venous stasis.
Progesterone stimulates increased respiratory drive, leading to higher tidal volume and minute ventilation. Oxygen consumption increases by 20%. Although respiratory rate remains stable, mild respiratory alkalosis may occur. The diaphragm elevates due to uterine enlargement, but lung function is generally preserved.
Renal blood flow and glomerular filtration rate increase by 40–60%, enhancing clearance of waste products. Ureters and renal pelvis dilate, especially on the right, leading to physiological hydronephrosis. There is increased urinary frequency and a higher risk of urinary tract infections.
Hormonal effects, especially from progesterone, slow gastrointestinal motility, leading to constipation and reflux. Nausea and vomiting (morning sickness) are common in the first trimester. Gallbladder motility is reduced, increasing the risk of gallstones.
There is increased activity of the thyroid and adrenal glands. Insulin resistance develops in the second half of pregnancy, influenced by placental hormones, potentially leading to gestational diabetes. Basal metabolic rate rises to meet fetal and maternal energy demands.
Red cell mass increases, but plasma volume rises more significantly, causing dilutional (physiological) anemia. White blood cell counts may be elevated. There is a hypercoagulable state due to increased clotting factors, reducing hemorrhage risk but increasing thromboembolic risk.
Relaxin and progesterone cause ligamentous laxity, especially in the pelvis. The growing uterus shifts the center of gravity, causing lumbar lordosis and back pain. These adaptations prepare the body for delivery but may result in discomfort.
Estrogen and melanocyte-stimulating hormone cause hyperpigmentation, including linea nigra and melasma. Stretch marks (striae gravidarum) may appear due to rapid skin stretching. Increased blood flow may cause skin warmth and redness.
Breast enlargement, tenderness, and darkening of the areolae occur due to hormonal stimulation. Colostrum may be produced in late pregnancy. The uterus grows exponentially, and the cervix softens (Goodell’s sign) and becomes more vascular (Chadwick’s sign).
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| Physiological changes during pregnancy |
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