From the Guidelines
Pregnancy induces widespread changes across all body systems, prioritizing fetal development and preparation for childbirth, with the most significant alterations occurring in the cardiovascular, respiratory, renal, and endocrine systems. The cardiovascular system undergoes notable changes, including a 30-50% increase in cardiac output and blood volume, as well as a 10-20 beats per minute increase in heart rate 1. Blood pressure typically decreases in the first and second trimesters due to peripheral vasodilation before returning to normal in the third trimester.
Key Changes by System
- Cardiovascular: Increased cardiac output, blood volume, and heart rate, with decreased systemic vascular resistance and blood pressure in early pregnancy 1.
- Respiratory: Increased tidal volume and minute ventilation, with a decrease in functional residual capacity as the uterus enlarges and elevates the diaphragm 1.
- Renal: Increased glomerular filtration rate and renal plasma flow, with the ureters dilating due to hormonal influences 1.
- Endocrine: Profound changes with the placenta producing hormones like human chorionic gonadotropin, estrogen, and progesterone that drive many physiological adaptations throughout pregnancy.
- Gastrointestinal: Decreased motility leading to constipation, heartburn from relaxed esophageal sphincter, and nausea/vomiting particularly in early pregnancy.
- Musculoskeletal: Ligament laxity due to relaxin hormone, leading to altered posture and potential back pain.
- Skin: Hyperpigmentation, stretch marks, and increased oil production.
- Hematological: Physiologic anemia from plasma volume expanding more than red cell mass, along with increased clotting factors creating a hypercoagulable state.
These changes are essential for supporting fetal development and preparing the mother's body for childbirth, and understanding them is crucial for managing pregnancy-related complications and ensuring the best possible outcomes for both mother and fetus. The most recent and highest quality evidence supports the notion that these physiological changes are critical for a healthy pregnancy 1.
From the Research
Physiological Changes During Pregnancy
The various body system changes that occur during pregnancy include:
- Cardiovascular changes, such as sinus tachycardia, systolic heart murmurs, and cardiac enlargement 2
- Respiratory changes, affecting the respiratory system 3
- Renal changes, affecting the renal system 3
- Gastrointestinal changes, affecting the gastrointestinal system 3
- Hematologic changes, affecting the hematologic system 3
- Biochemical changes, affecting biochemical levels 4, 2
Organ Systems Affected
Almost all organ systems are affected by the physiological changes that occur during pregnancy, including:
- Cardiovascular system 3, 2
- Respiratory system 3
- Renal system 3
- Gastrointestinal system 3
- Hematologic system 3
- Placenta, adding another layer of complexity 3
Importance of Understanding Physiological Changes
Understanding these physiological changes is crucial for clinicians to: