Physiological Changes in Pregnancy

Introduction

• Speaker: Dr. Shonali Chandra
• Focus: Important physiological changes during pregnancy and their clinical implications.
• Reference code for subscription discount: SHONALI (10% off subscription package)

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• Special live session on prenatal screening at 8 PM

Reproductive Tract Changes

Growth of the Uterus

• Weight of non-pregnant uterus: 50-70 grams
• Weight of pregnant uterus at term: 1100 grams
• Capacity: Approximately 5 liters
• Responsible changes: Myometrial hypertrophy and hyperplasia (estrogen related)
  • Hypertrophy is more predominant than hyperplasia
• Hypertrophy and hyperplasia mainly occur in the first 12 weeks
• Postpartum, uterus weight remains around 100 grams

Layers of Myometrium

• Three distinct layers:
  • Outer longitudinal layer
  • Inner circular layer
  • Middle layer (most important for controlling blood loss post-delivery)
• Contraction of myometrial fibers constricts blood vessels, controlling postpartum hemorrhage.

Clinical Implications

• Uterus becomes palpable per abdomen by 12 weeks of gestation
• Round ligament pain due to stretching leading to unilateral sharp pain, often worsened by movement.
  • Treatment: Counsel about normalcy, local heat application, and avoiding jerky movements.
• Dextrorotation of uterus due to left-side pelvic filling (risk of supine hypotension syndrome).
• Preferred position: Left lateral position to alleviate pressure on inferior vena cava.

Changes in the Vagina

• Increased vascularity results in Chadwick's sign (bluish hue).
• Vaginal pH becomes more acidic (around 3.5), promoting vulvovaginal candidiasis (most common vaginitis).

Breast Changes

• Breast tenderness and changes due to hypertrophy and proliferation of ducts and alveoli, primarily influenced by estrogen and progesterone.
• Montgomery tubercles (hypertrophied sebaceous glands) become prominent.
• Colostrum can be expressed as early as 12 weeks.

Cutaneous Changes

• Striae gravidarum (stretch marks)
• Linea nigra (dark line from pubic symphysis to umbilicus)
• Cloasma/melasma (facial pigmentation) due to increased estrogen.

Metabolic Changes

• Increased blood volume (40-50%) and plasma volume (up to 50%).
• Hemodilution leads to physiological anemia (lower hemoglobin concentration).
• Increased iron requirement: 1000 mg during pregnancy (300 mg for fetus, 500 mg for RBC mass increase).
• Normal hemoglobin levels in pregnancy: less than 11 g/dL for anemia diagnosis.

Thyroid Changes

• Increased demand for thyroid hormones due to maternal and fetal needs.
• TSH levels are lower in the first trimester (due to HCG stimulation) and rise again in later trimesters.
• Clinical implications for diagnosing hypothyroidism in pregnancy (adjusted upper limit for TSH).

Calcium Metabolism

• Increased calcium absorption required due to fetal needs (30 grams).
• Serum calcium increases, while ionized calcium remains the same.

Conclusion

• Next session will cover systemic changes and their clinical implications.
• Importance of understanding physiological changes for better patient care.

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• Reminder: Check special classes for additional resources.