Pregnancy, Maternal Physiology

Estimated 6.4 million pregnancies in USA, resulting in 4.1 million live births per year.

Pregnancy rate is 102 pregnancies per 1000 women between the ages of 15–44 y.

Maternal mortality rate is 28 deaths per 100,000 live births in USA, with 210 deaths per 100,000 live births in the world.

Hemorrhage, hypertension, and embolic disorders are leading causes of maternal deaths.

Risks of maternal mortality include advanced maternal age, obesity, multifetal pregnancies, C-section, and African American race.

Difficult airway, including inability to intubate and ventilate due to maternal wt gain, breast enlargement, and swelling of oropharyngeal tissues (incidence of failed intubation 1:280 vs. 1:2230 in nonpregnant pts).

Hypoxemia occurs more quickly during periods of apnea due to decreasing FRC and increasing O ₂ consumption.

Aortocaval compression causing decreased uteroplacental perfusion and FHR late decelerations.

Hypercoagulability causing DVT/PE.

Obesity as an independent risk factor for adverse pregnancy outcomes.

Physiologic changes occur during pregnancy to allow maternal adaptation to the demands of the growing fetus and supporting placental unit and ultimately to facilitate labor and delivery.

These changes affect almost every organ system and influence the anesthetic and periop management of the pregnant woman.

Adjust drug doses and administration schedules to compensate for increased volume of distribution, decreased peak plasma drug concentration, increased elimination T _½ , and increased renal excretion.

Profound increases in hormonal concentrations, especially progesterone

Mechanical effects of an enlarging uterus

Increased metabolic demand

Presence of the low resistance placental circulation