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📘 Physiological Changes During Pregnancy

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GENITAL ORGANS

Vulva

• Becomes edematous and more vascular
• Superficial varicosities may appear (especially in multiparae)
• Labia minora: pigmented and hypertrophied

Vagina

• Walls: hypertrophied, edematous, more vascular
• Bluish coloration of mucosa = Jacquemier's sign
• Anterior vaginal wall length increases
• Secretion: copious, thin, curdy white; pH acidic (3.5-6) due to glycogen → lactic acid conversion by Lactobacillus acidophilus → prevents pathogenic multiplication
• Cytology: preponderance of navicular cells in cluster + plenty of Lactobacillus

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UTERUS

General

• Non-pregnant: weighs 60 g, cavity 5-10 mL, length 7.5 cm
• At term: weighs 900-1,000 g, measures 35 cm in length
• Capacity increased by 500-1,000 times

Enlargement Factors

1. Hypertrophy & Hyperplasia of muscle fibers (first half, under estrogen + progesterone; limited to first 12 weeks)
2. Stretching beyond 20 weeks due to growing fetus (wall becomes thinner, at term ~1.5 cm or less)

Muscle Fiber Arrangement (3 layers)

• Outer longitudinal: hood-like, continuous with round ligaments
• Inner circular: scanty, sphincter-like around tubal orifices and internal os
• Intermediate (thickest): criss-cross arrangement; blood vessels run through = Living Ligature (figure-of-8 form)

Vascular Changes

• Blood supply increases 8-fold by 20 weeks (mainly via uterine artery)
• Doppler: uterine artery diameter doubles
• Veins: dilated, valveless; numerous lymphatic channels open

Shape Changes

• 12 weeks: globular
• 28 weeks: pyriform/ovoid
• Beyond 36 weeks: spherical

Position

• Normal anteverted position exaggerated up to 8 weeks → may lie on bladder → urinary frequency
• Then becomes erect
• Lateral obliquity/Dextrorotation (rotates on long axis to right due to rectosigmoid on left)
• Cervix deviated to left side = Levorotation → cervix brought closer to ureter

Braxton-Hicks Contractions

• From very early weeks; spontaneous
• Irregular, infrequent, spasmodic, painless
• No effect on cervical dilatation
• NOT felt in abdominal pregnancy
• Near term: become frequent, may cause discomfort

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ISTHMUS

• Hypertrophies and elongates to ~3× original length in 1st trimester
• Beyond 12 weeks: progressively unfolds downward → incorporated into uterine cavity
• Circularly arranged muscle fibers act as sphincter in early pregnancy (retains fetus)
• Incompetency → mid-trimester abortion (cerclage operation principle)

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CERVIX

Stroma

• Hypertrophy & hyperplasia of elastic/connective tissues
• Fluids accumulate; vascularity increased
• Bluish coloration (squamous epithelium of portio vaginalis)
• Marked hypertrophy of glands → Goodell's sign (softening, evident from 6 weeks)

Epithelium

• Marked proliferation of endocervical mucosa with downward extension beyond squamocolumnar junction
• → Clinical appearance of ectopy (erosion) cervix
• Squamous cells may simulate basal cell hyperplasia or CIN (hormone-induced, regress after delivery)

Secretion

• Copious, tenacious (progesterone effect)
• Rich in matrix metalloproteinase, IgG, IgA
• Microscopy: fragmentation/crystallization (beading) due to progesterone

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FALLOPIAN TUBE

• Rises up; fimbrial end held by infundibulopelvic ligament → almost vertical
• Length somewhat increased
• Tube congested; muscles hypertrophy; epithelium flattened
• Patches of decidual reaction observed

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OVARY

• Corpus luteum: maximum at 8 weeks (2.5 cm, bright orange, cystic → yellow → pale)
• Regression follows decline in hCG
• Both ovarian and uterine cycles of normal menstruation remain suspended
• Luteoma of pregnancy = exaggerated luteinization reaction
• Decidual reaction may appear on outer surface of ovary

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BREASTS

• Changes best evident in primigravida
• Size: increases early (hypertrophy of ducts - estrogen; alveoli - progesterone)
• Nipples & Areola: larger, erectile, deeply pigmented; sebaceous glands (5-15) hypertrophied = Montgomery's tubercles; outer zone of irregular pigmentation in 2nd trimester = secondary areola
• Secretion: colostrum from ~12 weeks (sticky → thick, yellowish by 16 weeks)
  • Demonstration of secretion from a woman who has never lactated = important sign of pregnancy

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CUTANEOUS CHANGES

Pigmentation

1. Face: Chloasma gravidarum (pregnancy mask) - pigmentation around cheeks, forehead, eyes; disappears after delivery
2. Breast: already described
3. Abdomen:
   • Linea nigra: brownish-black midline from xiphisternum to symphysis pubis
   • Due to Melanocyte Stimulating Hormone (MSH) from anterior pituitary
   • Striae gravidarum: depressed linear marks (below umbilicus, thighs, breasts) - scar tissue in deeper layer of cutis; become striae albicans (glistening white) after delivery

Other Cutaneous Changes

• Vascular spider, palmar erythema (due to high estrogen)
• Mild hirsutism (excess hair lost in puerperium)

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WEIGHT GAIN IN PREGNANCY

BMI-Based Recommendations

• Rapid gain >0.5 kg/week or >2 kg/month in later months → possible pre-eclampsia
• Stationary/falling weight → IUGR or intrauterine fetal death

Sodium Retention - Causes

1. Increased estrogen and progesterone
2. Increased aldosterone (renin-angiotensin activation)
3. Increased antidiuretic hormone

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BODY WATER METABOLISM

• Water retained at term: ~6.5 liters
• Water content of fetus + placenta + amniotic fluid: ~3.5 liters
• Pregnancy is a state of hypervolemia
• Active retention of sodium (900 mEq), potassium (300 mEq), and water