2- Maternal Phsiology Changes in Pregnancy

Maternal Physiological Changes in Pregnancy

• Anatomical, physiological, and biochemical adaptations in pregnancy are profound.
• Physiological adaptations of normal pregnancy can be misinterpreted as pathological, and can mask or worsen pre-existing diseases.
• Physiological changes occur in the nervous system, musculoskeletal system, endocrine system, cardiovascular system, respiratory system, urinary system, and reproductive tract.

Reproductive Tract: Uterus

• Uterus stretches and hypertrophies.
• Corpus walls thicken during early pregnancy, then gradually thin.
• Uterine myometrium is 1-2 cm thick at term.
• Estrogen and progesterone likely influence uterine hypertrophy.
• Uterine size increases more rapidly in length than width during pregnancy, assuming an ovoid shape.

Reproductive Tract: Cervix

• Softening and cyanosis of the cervix result from increased vascularity and edema.
• Cervical glands proliferate and may extend or evert.
• Cervical mucus is rich in immunoglobulins and cytokines acting as an immunological barrier.
• Progesterone-induced changes in cervical mucus (ferning) may be observed.

Reproductive Tract: Ovaries

• Ovulation ceases during pregnancy.
• A single corpus luteum is present during the first 6-7 weeks post ovulation.
• Relatively little progesterone is produced after the initial weeks.
• An extrauterine decidual reaction occurs on and beneath the ovarian surface, commonly.
• Ovarian vascular pedicle diameter increases during pregnancy, from approximately 0.9 cm at early gestation to 2.6cm at term.

Reproductive Tract: Relaxin

• A protein hormone secreted by the corpus luteum and placenta.
• Its pattern of secretion mimics human chorionic gonadotropin (hCG).
• Involved in remodeling reproductive tract connective tissue.
• Related to augmented renal hemodynamics, decreased serum osmolality, and uterine artery compliance associated with normal pregnancy.

Reproductive Tract: Theca-Lutein Cysts

• Benign ovarian lesions resulting from exaggerated physiological follicle stimulation (hyperreactio luteinalis).
• Associated with high hCG levels.
• Asymptomatic, but hemorrhage can cause abdominal pain.
• Maternal virilization may be observed.

Reproductive Tract: Vagina and Perineum

• Increased vascularity and hyperemia develop in the skin and muscles of the perineum and vulva.
• Increased vascularity results in the characteristic violet color of Chadwick's sign.
• Mucosal thickness, connective tissue loosening, and smooth muscular cell hypertrophy occur.
• Vaginal discharge (thick, white) is acidic due to increased lactic acid production from glycogen.

Reproductive Tract: Breasts

• Tenderness and paresthesias are common.
• Breast size and delicate veins become visible closer to the surface.
• Nipples become more erectile, larger, and more deeply pigmented.
• Colostrum (thick, yellowish fluid) can be expressed from nipples.
• Areolae become broader and more deeply pigmented, appearing with small elevations (Montgomery glands).

Abdominal Wall

• Striae gravidarum (stretch marks) or reddish, depressed streaks, appear on abdominal skin.
• Increased melanocyte-stimulating hormone, estrogen, and progesterone contribute to pigmentation.
• Diastasis recti: rectus muscles separate, potentially forming a ventral hernia.
• Chloasma (melasma gravidarum): may occur as irregular patches on the face and neck.
• Linea nigra darkening of the midline of the anterior abdominal wall.

Skin Changes

• Vascular Changes (hyperestrogenemia): angiomas (spider veins), red skin elevations (branching out from a central lesion), and palmar erythema appear.

Metabolic Changes

• Weight gain averages 12.5 kg.
• Increased water retention occurs.

Electrolyte Metabolism

• Glomerular filtration rate (GFR) of Na and K increases, despite excretion remaining unchanged because of tubule resorption.
• Serum Ca levels decrease.
• Serum Mg also decreases.
• Iodine requirements increase.

Carbohydrate Metabolism

• Mild fasting hypoglycemia and postprandial hyperglycemia.
• Hyperinsulinemia.
• Suppression of glucagon.
• Increased insulin resistance and estrogen stimulation affect metabolism.

Fat Metabolism

• Maternal hyperlipidemia.
• Increase in lipids, lipoproteins, and apolipoproteins.
• Increase in insulin resistance and estrogen stimulation.
• Leptin levels rise to regulate maternal energy demands to regulate fetal growth.
• Elevated leptin levels correlate with preeclampsia and gestational diabetes mellitus (GDM).

Hematologic Changes

• Increased blood volume (40-45%).
• Meets metabolic demands of enlarging uterus and supports rapidly growing placenta.
• Plasma increases more than erythrocytes. Erythrocyte volume increase to 450 ml.
• Moderate erythrocyte hyperplasia occurs; reticulocyte count increases.
• Serum iron is required in larger amounts, with 1000 mg needed during normal gestation.

Cardiovascular System

• Cardiac output increases.
• Systemic vascular resistance decreases.
• Brachial systolic and diastolic blood pressure decrease.
• Central systolic blood pressure is also lower.
• Resting pulse rate increases by approximately 10 beats/min.
• Plasma volume expansion from weeks 10-20.
• Ventricular performance impacted by changes in systemic vascular resistance and pulsatile arterial flow.

Respiratory System

• Diaphragm rises 4 cm.
• Functional residual capacity decreases (20-30%).
• Expiratory reserve volume decreases (15-20%).
• Residual volume increases (20-125%).
• Inspiratory capacity increases (5-10%).
• Total lung capacity remains unchanged or decreases by less than 5%.

Urinary System

• Kidney size increases (approximately 1.5 cm).
• Glomerular filtration rate (GFR) and renal plasma flow increase early in pregnancy.
• GFR increases to 25–50% of its initial value by mid-pregnancy.

Renal Changes in Normal Pregnancy

• Decreased bicarbonate threshold.
• Progesterone stimulates respiratory center.
• Significant changes to osmolarity for AVP release and thirst are noted.
• Serum creatinine decreases with normal gestation.
• Alterations in various parameters like kidney size, and dilatation, renal function, and maintenance of acid-base, with clinical relevance.

Gastrointestinal Tract

• Pregnancy gingivitis: gums becoming hyperemic and softened with potential bleeding when traumatized.
• Epulis gravidarum: highly vascular swelling of the gums.
• Stomach and intestines displaced by enlarging uterus.
• Appendix displacement upward and somewhat laterally as uterus enlarges.

Pyrosis (heartburn)

• Esophageal reflux of acidic secretions.
• Danger of regurgitation and aspiration during general anesthesia.

Hemorrhoids

• Constipation and elevated venous pressure within the enlarged uterus likely contribute.

Endocrine System

• Pituitary gland enlarges (approximately 135%).
• Growth hormone predominantly secreted from the maternal pituitary during the first trimester.
• Growth hormone secretion from placenta increases by week 17.
• Prolactin levels increase markedly.

Musculoskeletal System

• Progressive lordosis is characteristic.
• Sacroiliac, sacrococcygeal, and pubic joints have increased mobility.
• Symphyseal separation accompanies deliveries, with significant pain when greater than 1cm.

Central Nervous System

• Pregnancy-related memory decline is limited to third trimester.
• This decline is not attributable to depression, anxiety, sleep deprivation, or other physical changes in pregnancy.
• Intraocular pressure decreases and is attributed to increased vitreous outflow.
• Corneal sensitivity decreases.
• Krukenberg spindles are brownish-red opacities in posterior surface of cornea.