Genitourinary System

■ Urinary stasis secondary to decreased ureteral peristalsis and mechanical uterine compression of the ureter at pelvic brim as pregnancy progresses

■ Asymptomatic bacteruria occurs in 5 to 8% of pregnant women.

■ Urinary frequency increases:

■ During first 3 months of pregnancy due to bladder compression by enlarging uterus

■ During last week of pregnancy as the fetal head descends into pelvis

■ Physiologic after T1

■ Passing urine four times per night is normal

■ Fetal movements and insomnia contribute to the nocturia

■ Stress incontinence:

■ Occurs frequently during normal pregnancy

Decreased GI motility may be responsible for the increased absorption of water, Na+, and other substances.

The superior rectal vein is part of the portal system and has no valves, hence the high pressure within the system is communicated to the pelvic veins and produces hemorrhoids.

The increase in cholestasis plus increase in lipids and cholesterol lead to higher incidence of gallstones, cholecystitis, and biliary obstruction.

Albumin concentration falls by 22%% despite the increase in synthetic rate due to hemodilution.

Bacteruria + urinary stasis predispose patients to pyelonephritis, the most common nonobstetric cause for hospitalization during pregnancy.

If frequency occurs in conjunction with dysuria, hematuria,urgency/ hesitancy, flank pain, or should be evaluated for a UTI/cystitis +/pyelonephritis.

In pregnancy, the increased rate of renal clearance ^ reduced effective dose of antibiotics.

GFR increases ^ quantity of glucose filtered in urine is greater than in nonpregnant state ^ tubular threshold for glucose is exceeded ^ glycosuria is detected in 50% of pregnant women.

■ Due to relaxation of the bladder supports

■ The urethra normally elongates during pregnancy, but not in those who develop stress incontinence.

Bladder

Bladder tone decreases, but bladder capacity increases progressively during pregnancy.

Ureters

Ureters undergo progressive dilatation and kinking in > 90% of pregnant women at > 6 weeks

■ Accompanied by a decreased urine flow rate

■ Dilatation is greater on right secondary to dextrorotation of the uterus, and does not extend below the pelvic brim.

■ Dilatation is secondary to the physical obstruction by the pregnant uterus and the effects of pregnancy hormones.

■ Ureteric dilatation extends up to the calyces ^ increased glomerular size and increased interstitial fluid ^ enlarged kidneys (length increases by 1 cm and weight increases by 20%).

Renal Function

■ Renal plasma flow increases from T1, reaching 30 to 50% above non-pregnant levels by 20 weeks. Flow remains elevated until 30 weeks and then slowly declines to nonpregnant levels postpartum.

■ Glomerular filtration rate (GFR) increases soon after conception. It reaches 60% above nonpregnant level by 16 weeks and remains elevated for remainder of pregnancy.

Renal Tubule Changes

Tubular function changes:

■ Tubules lose some of their resorptive capacity—amino acids, uric acid, and glucose are not as completely absorbed in the pregnant female.

■ Results in an increase in protein loss of up to 300 mg/24 hr

Renal retention of Na+ results in water retention. Mother and conceptus increase their Na+ content by 500 to 900 nmol (due to increased reabsorption by renal tubules).

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