1. Cardiovascular Changes
Physiological Adaptations:
- Increased Blood Volume → ↑ 40–50% (Peaks at 32 weeks).
- Increased Cardiac Output (CO) → ↑ 30–50% (To meet fetal oxygen demands).
- Decreased Systemic Vascular Resistance (SVR) → Due to progesterone-mediated vasodilation.
- Slightly Increased Heart Rate (HR) → ↑ 10–15 bpm.
- Blood Pressure Changes:
- First & Second Trimester: ↓ BP (Due to vasodilation).
- Third Trimester: Returns to pre-pregnancy levels.
Clinical Importance:
- Supine Hypotensive Syndrome → Uterus compresses IVC, reducing venous return. Management: Left lateral position.
- Physiological Murmurs → Common due to increased blood flow.
2. Hematological Changes
Blood Composition Adaptations:
- Plasma Volume ↑ 50%, RBC Mass ↑ 20% → Causes physiological anemia of pregnancy.
- Increased WBC Count → Mild leukocytosis (WBC ~12,000–16,000/mm³).
- Hypercoagulable State →
- ↑ Clotting Factors (Fibrinogen, Factors VII, VIII, IX, X).
- ↓ Fibrinolysis → Increased risk of DVT/PE.
Clinical Importance:
- Anemia of Pregnancy: Hb <11 g/dL (Due to dilution effect).
- Increased Risk of Thrombosis: DVT, PE risk is higher postpartum.
3. Respiratory Changes
Adaptations:
- Increased Oxygen Demand → ↑ 20–30% due to fetal metabolism.
- Increased Tidal Volume & Minute Ventilation → Due to progesterone stimulation.
- Decreased Functional Residual Capacity (FRC) → ↓ 20% (Uterus elevates diaphragm).
Clinical Importance:
- Dyspnea of Pregnancy → Normal but must be differentiated from pulmonary embolism.
- Mild Respiratory Alkalosis → pH ~7.4–7.45, PaCO₂ ~30 mmHg.
4. Renal Changes
Adaptations:
- Increased Renal Blood Flow & GFR → ↑ 50% (For waste elimination).
- Increased Sodium & Water Retention → Leads to mild edema.
- Decreased Serum Creatinine & Urea → Normal Cr in pregnancy ~0.4–0.8 mg/dL.
Clinical Importance:
- Mild Glycosuria & Proteinuria are normal (<300 mg/day).
- Gestational Hydronephrosis → Ureteral dilation due to progesterone effect.
5. Endocrine & Metabolic Changes
Hormonal Adaptations:
- hCG (Human Chorionic Gonadotropin) → Maintains corpus luteum.
- Increased Estrogen & Progesterone → Supports pregnancy.
- Human Placental Lactogen (hPL) → Causes insulin resistance → Gestational Diabetes Risk.
Metabolic Changes:
- Increased Insulin Resistance → Higher postprandial glucose levels.
- Increased Fat Storage for Fetal Energy Needs.
Clinical Importance:
- Gestational Diabetes Mellitus (GDM) → Diagnosed by OGTT at 24–28 weeks.
- Increased Risk of Hypoglycemia in Fasting State.
6. Gastrointestinal (GI) Changes
Adaptations:
- Decreased GI Motility → Due to progesterone relaxing smooth muscles.
- Decreased Lower Esophageal Sphincter Tone → Leads to GERD/Reflux.
- Gallbladder Sluggishness → Increased risk of gallstones.
Clinical Importance:
- Constipation & Hemorrhoids → Due to slow bowel motility.
- GERD in Pregnancy → Managed with lifestyle changes & antacids.
7. Musculoskeletal & Skin Changes
- Increased Lumbar Lordosis → To accommodate uterine weight.
- Increased Joint Laxity → Due to relaxin & progesterone.
- Hyperpigmentation:
- Chloasma ("Mask of Pregnancy") → Dark patches on face.
- Linea Nigra → Midline abdominal pigmentation.
Striae Gravidarum (Stretch Marks) → Due to dermal collagen changes.
Summary Table: Pregnancy-Induced Changes
|
System |
Changes |
Clinical Relevance |
|
Cardiovascular |
↑ Blood volume, ↑ CO, ↓ BP in 1st & 2nd
trimester |
Supine hypotension, Physiological murmur |
|
Hematological |
↑ Plasma volume, Mild anemia, Hypercoagulability |
Risk of DVT, PE |
|
Respiratory |
↑ Oxygen demand, Mild alkalosis |
Dyspnea of pregnancy |
|
Renal |
↑ GFR, ↓ Cr, Glycosuria |
Gestational hydronephrosis |
|
Endocrine |
↑ Insulin resistance, ↑ hPL |
Gestational diabetes risk |
|
Gastrointestinal |
↓ Motility, GERD, Constipation |
Reflux, Gallstones |
|
Musculoskeletal |
Lordosis, Joint laxity, Hyperpigmentation |
Back pain, Striae gravidarum |
Key Takeaways
- Blood volume & CO increase to meet fetal demands.
- Hypercoagulability increases risk of DVT/PE postpartum.
- Increased insulin resistance can lead to Gestational Diabetes.
- GI motility decreases, leading to GERD & constipation.
