Pregnancy changes nearly every body system to support the fetus and prepare for birth and breastfeeding. Most changes are driven by hormones and by the growing uterus. Knowing what is normal lets the nurse recognize what is not.

Key hormones

Signs of pregnancy

A positive hCG test is only probable, because other conditions (molar pregnancy, some tumors) produce hCG.

Cardiovascular

• Blood volume rises about 40–50%, starting in the first trimester; plasma volume rises more than red cell mass → physiologic (dilutional) anemia
• Cardiac output rises about 30–50%, peaking in the late second to early third trimester (about 28–32 weeks) and staying high; it rises further in labor and immediately after birth
• Heart rate increases about 10–15/min
• Blood pressure falls in the second trimester (lowest around mid-pregnancy) because of lower systemic vascular resistance, then returns toward baseline at term. Rising BP is never normal
• Heart displaced upward and to the left; soft systolic flow murmurs and an S₃ may be normal
• Supine hypotensive syndrome (after about 20 weeks): the uterus compresses the inferior vena cava → dizziness, pallor, hypotension, reduced placental flow → turn to the left side or tilt with a wedge
• Dependent edema of the ankles, varicose veins, hemorrhoids (venous pressure, progesterone)

Hematologic

• Hemoglobin normally stays at or above 11 g/dL (110 g/L) in the first and third trimesters and at or above 10.5 g/dL (105 g/L) in the second; lower values indicate anemia
• Serum iron and ferritin fall because of dilution and fetal demand — iron needs rise (27 mg/day)
• Hypercoagulable state: fibrinogen and clotting factors (VII, VIII, IX, X) increase, fibrinolysis decreases → protects against hemorrhage at birth but raises VTE risk (highest postpartum)
• WBC count rises (often up to about 15,000/mm³; higher in labor); platelets may fall slightly (gestational thrombocytopenia)

Respiratory

• Oxygen consumption rises about 15–20%
• Tidal volume and minute ventilation rise about 30–50% (progesterone) → mild compensated respiratory alkalosis (lower PaCO₂, about 30 mmHg; bicarbonate falls to compensate). Respiratory rate changes little
• Diaphragm rises about 4 cm; chest widens → functional residual capacity and expiratory reserve volume decrease → less oxygen reserve (desaturates faster during apnea)
• Nasal congestion, nosebleeds (estrogen-induced vascular congestion); dyspnea late in pregnancy is common but should be mild

Renal and urinary

• Renal plasma flow and GFR increase about 50% → serum creatinine and BUN fall (creatinine often 0.4–0.8 mg/dL (35–70 µmol/L)); a "normal" nonpregnant value may indicate kidney impairment
• Glycosuria can occur at normal blood glucose because filtered glucose exceeds tubular reabsorption
• Ureters and renal pelvis dilate (progesterone plus uterine compression, right more than left) → urinary stasis → higher risk of UTI and pyelonephritis; asymptomatic bacteriuria is treated
• Urinary frequency in the first trimester (uterus presses on bladder) and again in the third (fetal head descends)

Gastrointestinal

• Nausea and vomiting (first trimester; hCG and estrogen)
• Gums swollen, hyperemic, bleed easily (gingivitis, epulis); excess saliva (ptyalism)
• Heartburn — lower esophageal sphincter relaxes (progesterone), uterus pushes stomach up
• Slowed intestinal motility → constipation, bloating; hemorrhoids
• Gallbladder emptying slows → gallstone risk; alkaline phosphatase rises (placental origin); albumin falls
• Pica (cravings for nonfood items) — assess for iron deficiency

Integumentary

• Chloasma (melasma, "mask of pregnancy"), linea nigra, darkened areolae — from increased melanocyte-stimulating hormone and estrogen
• Striae gravidarum — stretch marks on abdomen, breasts, thighs; fade to silvery lines but do not fully disappear
• Spider angiomas and palmar erythema (estrogen)

Musculoskeletal

• Lumbar lordosis increases as the center of gravity shifts forward → low back pain
• Relaxin and progesterone loosen the sacroiliac joints and symphysis pubis → pelvic instability, back and pelvic pain, "waddling" gait, fall risk
• Diastasis recti; leg cramps; carpal tunnel symptoms from fluid retention

Reproductive and breasts

• Uterus grows from about 60 g to about 1,000 g; fundus: symphysis at 12 weeks, umbilicus at 20 weeks, near the xiphoid at 36 weeks; drops slightly with lightening near term
• Braxton Hicks contractions — irregular, painless tightening
• Increased vaginal discharge (leukorrhea); cervical mucus plug forms
• Breasts enlarge and become tender; colostrum may leak from the second trimester; Montgomery tubercles enlarge

Endocrine–metabolic

• First half: insulin sensitivity is normal or increased — risk of hypoglycemia with nausea
• Second half: insulin resistance (hPL, cortisol, progesterone, estrogen) → higher post-meal glucose; unmasks gestational diabetes
• Thyroid enlarges slightly; basal metabolic rate rises

Normal laboratory changes in pregnancy

Recommended total weight gain by prepregnancy BMI (IOM/NAM 2009)

• About 0.5–2 kg (1–4.5 lb) in the first trimester; afterward about 0.4 kg (1 lb) per week for normal-weight clients
• Most of the gain is fetus, placenta, amniotic fluid, uterus, breasts, blood volume, extracellular fluid, and fat stores
• Weight loss or strict dieting is not recommended in pregnancy, even with obesity

Listed in priority order.

1. Prevent supine hypotension — position in lateral tilt (usually left) for exams and rest after 20 weeks; left uterine displacement during resuscitation
2. Differentiate normal from abnormal: rising BP, sudden edema of face and hands, severe headache, visual changes, significant dyspnea or chest pain, fever with flank pain, and vaginal bleeding are not normal changes
3. Fall prevention — changed center of gravity and joint laxity
4. Interpret labs with pregnancy norms (e.g., creatinine above about 0.9 mg/dL (80 µmol/L) needs evaluation; above 1.1 mg/dL (97 µmol/L) is a severe feature of preeclampsia)
5. Relieve common discomforts (see Client Education)

• Nausea: small frequent meals, dry crackers before rising, avoid strong odors and fatty foods
• Heartburn: small meals, stay upright for about 1–2 hours after eating, raise the head of the bed; use antacids approved by the clinician (avoid sodium bicarbonate)
• Constipation: fluids, fiber, activity
• Back pain: good posture, pelvic tilt exercises, low-heeled supportive shoes, proper body mechanics
• Dependent edema and varicose veins: elevate legs, avoid prolonged standing and crossed legs, compression stockings
• Gums: soft toothbrush; routine dental care is safe and recommended in pregnancy
• Leg cramps: stretch by dorsiflexing the foot
• Faintness: rise slowly, avoid lying flat on the back
• Urinary frequency: void often, do not reduce fluids, Kegel exercises; report burning or flank pain
• Skin changes usually fade after birth; stretch marks lighten but may remain; use sunscreen for melasma

• Plasma volume rises more than RBC mass → physiologic anemia
• Cardiac output ↑ 30–50%, peaks about 28–32 weeks; HR ↑ 10–15/min; BP lowest in second trimester
• Supine hypotension after 20 weeks → left lateral position
• Hypercoagulable (↑ fibrinogen, factors) → VTE risk
• Minute ventilation ↑, FRC ↓, compensated respiratory alkalosis
• GFR ↑ 50% → creatinine ↓; glycosuria can be normal; ureteral dilation → UTI risk
• Progesterone = smooth-muscle relaxation, ↑ temperature; relaxin = joint laxity, back pain
• Gum hyperemia and bleeding are normal; heartburn and constipation from slowed motility
• Striae gravidarum, chloasma, linea nigra
• Prolactin rises in pregnancy; hPL → insulin resistance in the second half
• Signs: Chadwick (bluish cervix), Goodell (soft cervix), Hegar (soft lower segment) = probable; fetal heart/ultrasound = positive
• Weight gain for normal BMI: 11.5–16 kg (25–35 lb)