Pregnancy, also known as gestation, is the period of approximately 9 months (about 40 weeks from the last menstrual period) during which one or more offspring develops inside a woman's uterus. It is a complex physiological process that begins with the implantation of a fertilized egg (embryo) into the uterine wall and ends with the birth of a baby.
Source: Cleveland Clinic & NIH
Functions of Pregnancy
The primary function of pregnancy is to support the growth, development, and nourishment of the fetus.
- Fetal Development: The body creates an environment for the embryo to grow from a single cell into a fully developed infant.
- Placental Function: A vital life-support system that provides oxygen and nutrients from the mother’s blood while removing waste products.
- Hormonal Shift: Massive changes driven by hormones like progesterone and estrogen maintain the uterine lining and support the pregnancy.
Source: National Institutes of Health (.gov)
Physiological Changes & Health
To sustain a growing fetus, nearly all maternal organ systems undergo immense adaptation:
Cardiovascular & Respiratory
- Cardiovascular: Blood volume increases by 45-55% to support the uterus.
- Respiratory: Higher oxygen demands increase tidal volume by 30-40%, often leading to increased breathing rates.
Gastrointestinal & Musculoskeletal
- Gastrointestinal: Progesterone relaxes smooth muscles, often causing heartburn, constipation, or slow stomach emptying.
- Musculoskeletal: A shift in the center of gravity increases lordosis (lower back strain), while relaxin increases joint laxity in the pelvis.
Endocrine & Metabolism
Metabolism shifts to prioritize nutrient delivery to the fetus, which can lead to increased insulin resistance in later trimesters.
Source: National Institutes of Health (.gov)
Common Symptoms & Trimesters
Pregnancy is divided into three trimesters, each spanning roughly 13 weeks.
- First Trimester: Morning sickness, fatigue, tender breasts, and missed periods.
- Second & Third Trimesters: Back pain, heartburn, swelling of extremities, and shortness of breath as the uterus expands.