Maternal Physiological Changes

Maternal Physiological Changes - Heart's Big Load

• Cardiac Output (CO): ↑ 30-50%; peaks 20-24 wks.
  • Early: ↑ Stroke Volume (SV).
  • Later: ↑ Heart Rate (HR) by 15-20 bpm.
• Blood Volume: ↑ 40-50%.
  • Plasma volume ↑ 40-50% > RBC mass ↑ 20-30% → physiological anemia.
• Systemic Vascular Resistance (SVR): ↓ (progesterone, PGs).
• Blood Pressure (BP):
  • Systolic: Slight ↓ or stable.
  • Diastolic: ↓ (nadir mid-preg), then ↑.
• Heart Sounds: Wide S1 split, S3. Systolic ejection murmur (flow, ~90%). Diastolic = PATHOLOGY.
• ECG: Left axis deviation.
• Supine Hypotension: IVC compression → ↓CO. Use left lateral position.
• 📌 Mnemonic: CO ↑, Blood Volume ↑, SVR ↓, Diastolic BP ↓.

  ⭐ Cardiac output increases by 30-50% during pregnancy, peaking around 20-24 weeks. oka

Maternal Physiological Changes - Breathing & Peeing

Respiratory System:

• Diaphragm: Elevated ~4 cm; Thoracic cage circumference ↑.
• Tidal Volume (TV) & Minute Ventilation (MV): ↑ 30-50%.
• Functional Residual Capacity (FRC) & Residual Volume (RV): ↓ 20%. Total Lung Capacity (TLC) slightly ↓.
• $PaCO_2$: ↓ to 27-32 mmHg (progesterone effect) → compensated respiratory alkalosis.
• Physiological dyspnea common.

Renal System:

• Kidneys: ↑ size; Glomerular Filtration Rate (GFR) & Renal Plasma Flow (RPF) ↑ by ~50%.
• Serum Creatinine & Blood Urea Nitrogen (BUN): ↓.
• Physiological hydronephrosis & hydroureter (Right > Left common).
• Glycosuria: Common (↓ tubular reabsorption of glucose).
• Urinary frequency & nocturia. Renin-Angiotensin-Aldosterone System (RAAS) activity ↑.

⭐ Progesterone is the primary stimulant for increased minute ventilation, leading to chronic compensated respiratory alkalosis with renal bicarbonate excretion.

Maternal Physiological Changes - Blood & Guts Shifts

• Blood Volume & Composition:
  • Plasma volume ↑ by 40-50%; Red Blood Cell (RBC) mass ↑ by 20-30%.
  • Physiological anemia: Hemoglobin (Hb) ↓ (e.g., < 11 g/dL in 1st trimester, < 10.5 g/dL in 2nd).
  • White Blood Cell (WBC) count (leukocytosis) ↑; Platelets may slightly ↓.
  • Hypercoagulable state: Fibrinogen ↑, Clotting Factors (VII, VIII, X) ↑. Erythrocyte Sedimentation Rate (ESR) ↑.
  • Iron requirement ↑ significantly (total ~1000 mg).
• Gastrointestinal System:
  • Nausea & Vomiting of Pregnancy (NVP): Common, linked to hCG.
  • ↓ Lower Esophageal Sphincter (LES) tone → Heartburn/GERD (progesterone effect).
  • ↓ GI motility → Constipation, ↑ nutrient absorption time.
  • Gallbladder: Stasis, ↓ contractility → ↑ risk of cholesterol gallstones.
  • Liver: Alkaline Phosphatase (ALP) ↑ (placental origin); serum albumin ↓ (hemodilution).

⭐ Plasma volume expansion significantly exceeds red cell mass increase, causing physiological hemodilution and a decrease in hemoglobin concentration, hematocrit, and red blood cell count.

Maternal Physiological Changes - Hormones & Body Mods

• Hormones:
  • hCG: Peaks 8-10 wks; maintains corpus luteum.
  • Progesterone (↑): Smooth muscle relaxation; supports pregnancy.
  • Estrogen (E3) (↑): Uterine/breast growth.
  • hPL/hCS (↑): Anti-insulin (↑ maternal glucose); lipolysis.
  • Relaxin (↑): Softens cervix, ligaments.
  • Prolactin (↑): Prepares lactation.
  • Cortisol (↑), Aldosterone (↑).
  • Thyroid: ↑TBG → ↑Total T4/T3. hCG may ↓TSH (1st trim).
• Body Modifications:
  • Weight Gain: Avg. 11-16 kg.
  • BMR: ↑ 15-20%.
  • Insulin Resistance: hPL, progesterone, cortisol driven.
  • Breast: ↑Size, tenderness; Montgomery's tubercles; colostrum (~16 wks).
  • Skin: Hyperpigmentation (linea nigra, melasma); striae; spider angiomata.

⭐ hPL (Human Placental Lactogen) is key for diabetogenic state of pregnancy, ensuring fetal glucose supply.

High‑Yield Points - ⚡ Biggest Takeaways

• Cardiac output ↑ 30-50%; SVR ↓; supine hypotension common.
• Plasma volume ↑ more than RBC mass, causing physiological anemia; hypercoagulable state.
• Tidal volume & minute ventilation ↑; PaCO2 ↓ (compensated respiratory alkalosis).
• GFR & renal plasma flow ↑ by 50%; mild proteinuria & glycosuria can be normal.
• ↑ Estrogen, progesterone, hCG, hPL; progressive insulin resistance.
• Uterine blood flow ↑ dramatically.
• Diaphragm elevated, AP chest diameter ↑; thoracic breathing predominates.