Physical and Anatomical Changes During Pregnancy

A. Physical Changes Observed During Pregnancy

The American College of Cardiology notes that darkening of the labia majora represents normal genital hyperpigmentation related to the hyperestrogenic state 1, 2
The American Heart Association states that Chadwick's sign (purplish discoloration of the cervix and vaginal walls) results from increased vascularity and venous congestion in the pelvic organs 3
The American College of Obstetricians and Gynecologists recommends that the fundal height of 24 cm corresponds appropriately to approximately 24 weeks gestation, following the general rule that symphysis-fundal height in centimeters approximates gestational age in weeks 4

The Endocrine Society notes that estrogen stimulates melanocytes, leading to darkening of the areolae, linea nigra, and genital tissues 1, 2
The American Heart Association states that estrogen causes vasodilation and increased vascular permeability, resulting in the purplish discoloration of cervix and vaginal walls (Chadwick's sign) 3
The American College of Obstetricians and Gynecologists recommends that progesterone increases minute ventilation by 20-40% above baseline by term, producing mild respiratory alkalosis 4

The American College of Obstetricians and Gynecologists states that uteroplacental blood flow increases from 50 mL/min to close to 1000 mL/min during pregnancy, receiving up to 20% of maternal cardiac output at term 4
The American Heart Association notes that uterine vascular reactivity is altered, characterized by reduced tone, enhanced vasodilation, and blunted vasoconstriction 4
The Society for Maternal-Fetal Medicine recommends that the enlarging uterus elevates the diaphragm and can compress the inferior vena cava in the supine position, potentially decreasing venous return 4, 6

The American Heart Association states that circulating plasma volume increases by approximately 50% during pregnancy, with blood volume and red blood cell mass increasing gradually 1, 2, 3
The American College of Cardiology notes that cardiac output increases by 30-50% during pregnancy, reaching maximum by 32 weeks gestation 1, 2, 5, 6
The American College of Obstetricians and Gynecologists recommends that left lateral positioning optimizes cardiac output by relieving vena caval compression 6, 7