From the Guidelines
Pregnancy induces significant changes across all body systems, including the cardiovascular, respiratory, renal, gastrointestinal, reproductive, musculoskeletal, and integumentary systems, to support fetal development and prepare for childbirth. The cardiovascular system undergoes dramatic changes, with blood volume increasing by 30-50%, cardiac output rising by 30-50%, and heart rate increasing by 10-15 beats per minute, as noted in the study by 1. Some key changes include:
- Increased cardiac output, renal blood flow, and glomerular filtration rate, which increase to ≈50% over baseline by the second trimester and persist until term 1
- Marked systemic vasodilation with decreased systemic vascular resistance and subsequent lower blood pressure, which characterizes early pregnancy starting at 4 to 6 weeks of gestation 1
- Increased plasma volume, which reaches a maximum of 40% to 50% higher than the prepregnancy baseline 1 The respiratory system adapts with increased tidal volume and minute ventilation, while the diaphragm elevates as the uterus grows, resulting in a mild respiratory alkalosis with compensatory renal excretion of bicarbonate 1. Metabolic changes include increased basal metabolic rate, insulin resistance, and weight gain of 25-35 pounds on average. The renal system experiences increased glomerular filtration rate by 50%, leading to more frequent urination, and glomerular hyperfiltration to accommodate the maternal role of fetal detoxification of metabolic byproducts and maintenance of maternal osmoregulation 1. Gastrointestinal changes include decreased motility causing constipation, heartburn from relaxed esophageal sphincter, and nausea/vomiting in early pregnancy, due to the effects of progesterone 1. The reproductive system undergoes the most obvious changes with uterine growth from 70g to 1100g, cervical softening, and breast enlargement in preparation for lactation. Musculoskeletal adaptations include increased joint laxity due to relaxin hormone and postural changes to accommodate the growing abdomen. The skin may develop striae gravidarum (stretch marks), hyperpigmentation, and increased oil production. These physiological adaptations are primarily driven by hormonal changes, particularly increased levels of estrogen, progesterone, and human chorionic gonadotropin, which collectively ensure optimal conditions for fetal development and maternal health during pregnancy, as supported by the studies 1.
From the Research
Body System Changes During Pregnancy
The following are the various body system changes that occur during pregnancy:
- Cardiovascular System: undergoes significant changes to accommodate the increased blood volume and cardiac output required to support the growing fetus 2, 3, 4
- Hematologic System: experiences changes in blood volume, blood pressure, and coagulation factors to support the increased metabolic demands of pregnancy 2, 3, 4
- Respiratory System: undergoes changes to increase oxygen supply to the fetus and support the increased metabolic demands of pregnancy 2, 3, 4
- Renal System: experiences changes in renal function, including increased glomerular filtration rate and changes in electrolyte balance 2, 3, 4
- Gastrointestinal System: undergoes changes to support the increased nutritional demands of pregnancy, including changes in digestion and absorption 2, 3, 4
- Immunologic System: experiences changes to support the development of the fetus and prevent rejection by the mother's immune system 2, 3
- Endocrine System: undergoes changes to support the development of the fetus and prepare the mother for labor and delivery, including changes in hormone production by the placenta 5
- Anatomical Changes: occur in various organ systems, including the uterus, cervix, and pelvic floor, to support the growing fetus and prepare for labor and delivery 3, 4