Physiological Changes of Pregnancy

Cardiovascular	40-50% plasma blood volume	Vasodilation, with resultant heart rate (15-20 bpm), stroke volume (20-30%), cardiac output (CO) (30-50%)	Uterine perfusion goes from 2% of CO to 17%
	¯ Systemic vascular resistance secondary to smooth muscle relaxation caused by progesterone	¯ BP (up to 21%) between 8-26 weeks	Preexisting HTN may be artificially masked
	Compression of venous and lymphatic drainage of legs	Leads to lower extremity edema, stasis, increased DVT risk, and resultant 10-30% ¯ in CO	Vena cava may be completely occluded in the supine position late in pregnancy
	Heart is displaced left and upward	Heart appears larger on chest film	Diagnosis of cardio-megaly should not be based on CXR alone
	Jugular venous distention after 20 weeks		These and other signs/ symptoms may mimic cardiac disease
	Development of systolic ejection murmur	Developed by up to 96% of gravidas	These and other signs/ symptoms may mimic cardiac disease
	estrogen leads to edema mucous production of nasopharynx	Gravidas commonly have congestion/stuffiness and may have epistaxis	Gravidas may complain of chronic cold-like symptoms
Pulmonary	Tidal Volume (30-40%)		All of these changes may lead to a relative dyspnea. 75% of women complain of dyspnea by term.
	¯ Total lung capacity (5%) from elevation of a diaphragm	Diaphragm may rise 4cm on chest film
	¯ Functional residual capacity (20%)
	Tidal volume and Minute ventilation (30-40%)	Leads to ¯ PaCO2 and a compensated respiratory alkalosis
Metabolic	protein and carbohydrate metabolism	One kilogram of extra protein is deposited to the placenta, uterus, fetus, breast tissue, hemoglobin, and plasma proteins
Nutrition	Caloric requirements by 200 kcal/day	Gain of 25-35 lbs throughout pregnancy
	protein requirement to 70-75 g/day
	Folate requirement (0.4 to 0.8 mg/day)	May lead to neural tube defects if not supplemented	PNV
Hematologic	40-50% in plasma blood volume, but only 20-30% in red cell volume	Leads to relative, dilutional anemia. These changes peak at 30-34 weeks	Screen for underlying anemia which may exacerbate physiologic anemia and provide iron
	WBC may increase as high as 20 mil/mL
	Platelet count may decrease to as low as 100-150 mil/mL
	¯ Factors XI, XIII	Alteration in these factors leads to hypercoagulability. Pregnancy also is a state of venous stasis and endothelial damage.
	procoagulant factors (Factors I (Fibrinogen), VII, VIII, IX, X)
Renal	Size of kidneys and ureters	Right ureter dilated > left ureter, both by mechanical effect of uterus and relaxation by progesterone	Increased incidence of pyelonephritis
	Mechanical compression and displacement of ureters		Increased incidence of pyelonephritis
	GFR by 50% (which may last until 20 weeks postpartum)	Values to 150-200 ml/min
	¯ BUN (from 13 to 9) and Creatinine (from 0.8 to 0.5)
	Glucosuria (due to saturated tubular reabsorption)
	Plasma rennin activity (5-10x) and angiotensin (4-5x)	Leads to aldosterone (2x) and sodium reabsorption
	Nocturia
Gastrointestinal	b-hCG, relaxation of smooth muscle	Leads to nausea and vomiting usually resolved by 14-16 weeks	70% of pregnancies affected by “morning sickness”
	gastric emptying time
	¯ gastroesophageal sphincter tone	Leads to acid reflux
	¯ colonic motility	Leads to water absorption and constipation	11-38% of gravidas complain of constipation
	Portal venous pressure	Dilation of portosystemic venous anastomoses	Hemorrhoids
	Uterine displacement of bowel	Appendix may be greatly displaced	Diagnosis of appendicitis made difficult
	¯ rate of gallbladder emptying, change of bile fliud	Leads to increased formation of gallstones	Retained bile salts may lead to pruritus
Endocrine	b-hCG
	estrogen	Leads to in thyroxine-binding globulin	Keep mother euthyroid in spite ¯ serum iodid levels
	human placental lactogen (hPL)	Causes lipolysis and antagonizes insulin
	progesterone	Relaxes smooth muscle
	Prolactin (10x at term)	Prepares breasts for lactation
	Alkaline phosphatase (2-4x)	Produced by placenta
Dermatologic	estrogen	Can lead to formation of spider angiomata and palmar erythema	Angiomata are seen in up to 70% of caucasians
	melanocyte stimulating hormone (MSH)	Hyperpigmentation of nipples, umbilicus, linea nigra, perineum, and face (melasma/chloasma). Nevi may increase in size and frequency.	Some hyper-pigmentation occurs in 90% of gestations. Chloasma occurs 70% of the time
	Stretch and steroids/estrogen lead to striae distensae (stretch marks)	These are permanent changes that will change from pink/purlple to white/silver with time	No effective prevention exists
	cortisol and placental androgens may lead to hirsutism	Face mostly affected
	hair loss 2-4 months after delivery	Telogen effluvium, usually restored by 6-142 months postpartum.
	acne	Related to oil production by sebaceous glands
Musculoskeletal	Gravid uterus leads to progressive lordosis of the spine in order to prevent change in the maternal center of gravity		Leads to lower back pain
Musculoskeletal	Relaxin leads to relaxation of the ligaments of pubic symphysis and sacroiliac joints, peaking between 28-32 weeks	Symphis width increases from 3-4 mm to nearly 8 mm	Leads to pain over pubis and in inner thighs
Other	Breasts enlarge during first 8 weeks due to vasocongestion, and afterwards from ductal and alveolar growth	Nipples and areaola enlarge and nipples become more mobile	Breast pain is common complaint early in pregnancy
Other	3% in corneal thickness due to edema, and ¯ intraocular pressure (10%)	Eyeglasses, contact lenses, or laser-eye surgery may be affected during pregnancy but will resolve within a few weeks postpartum
	vascularity and hyperemia of genital tract	Bluish discoloration of cervix (Chadwick’s sign); softening and cyanosis of cervix (Goodell’s sign)
	vascularity and hyperemia of the gums	Can lead to gingivial bleeding, superinfection

Nutrition