Pregnancy - physiology

Summary

This video provides an in-depth overview of the physiological changes that occur during pregnancy. It covers hormonal shifts, including rising estrogen and progesterone levels, and explains how they impact various organ systems. Key milestones such as ovulation, implantation, and fetal development are discussed, alongside common pregnancy symptoms like morning sickness, mood changes, and physical discomforts like back pain and varicose veins. The video also explains the cardiovascular, respiratory, renal, and musculoskeletal changes, offering valuable insights into how a woman's body adapts to support a growing fetus.

Takeaways

• 😀 Pregnancy causes a rise in estrogen and progesterone, which leads to numerous anatomical and physiological changes in the body.
• 🍼 Ovulation marks day zero, and fertilization occurs within 12-24 hours to form a zygote, which divides into a blastocyst on day four.
• 🤰 HCG, produced by trophoblast cells, helps maintain progesterone and estrogen production, preventing menstruation and confirming pregnancy.
• 👶 Pregnancy lasts around 40 weeks from the last menstrual period, but counting from ovulation, it lasts approximately 38 weeks.
• ❤️ During pregnancy, the cardiovascular system expands, increasing blood volume by 30-50%, leading to a rise in cardiac output and heart rate.
• 💧 The body experiences physiological anemia due to a larger increase in plasma volume than red blood cells during pregnancy.
• 💨 Pregnancy leads to changes in the respiratory system, such as increased tidal volume and minute volume, improving gas exchange for the fetus.
• 🚻 Hormonal changes during pregnancy relax smooth muscles, which can lead to constipation, heartburn, and urinary frequency.
• 🩸 Pregnancy is a hypercoagulable state due to increased clotting factors and platelet aggregation, increasing the risk of venous thromboembolism.
• 👚 Pregnant women typically gain 25-35 pounds, contributing to the growth of the fetus, uterus, placenta, and increased blood volume.
• 🤕 Pregnancy causes physical discomfort, including back pain, diastasis recti, and increased joint pain due to relaxed ligaments.

Q & A

What is the significance of estrogen and progesterone during pregnancy?

Estrogen and progesterone play a crucial role in regulating various anatomical and physiological changes during pregnancy. They prepare the uterus for implantation, support the placenta, and inhibit other ovarian follicles from maturing. Progesterone also helps relax muscles and dilate blood vessels.

When does ovulation occur and what happens during ovulation?

Ovulation occurs on day zero of the menstrual cycle, where the egg is ejected from the ovary. The ovarian follicle transforms into the corpus luteum, which starts producing estrogen and progesterone. The egg then has a 12-24 hour window to be fertilized by sperm.

What role does human chorionic gonadotropin (HCG) play in pregnancy?

HCG is produced by trophoblast cells starting around day eight after fertilization. It signals the corpus luteum to continue producing estrogen and progesterone, which are crucial for maintaining the pregnancy. HCG is also what pregnancy tests detect to confirm pregnancy.

Why do pregnancy weeks start from the last menstrual period?

Pregnancy is typically counted from the last menstrual period (LMP) because women usually know the start date of their last period, but not when ovulation occurs. This method adds about two weeks to the actual gestational age, resulting in a 40-week pregnancy counted from the LMP.

What is the physiological anemia of pregnancy?

Physiological anemia of pregnancy occurs because the blood volume increases by 30-50%, but the rise in plasma volume exceeds the increase in red blood cells. As a result, the hematocrit (percentage of red blood cells in blood) decreases, leading to mild anemia.

How does the cardiovascular system adapt to pregnancy?

During pregnancy, blood volume increases by up to 50%, and the heart rate rises by about 20 beats per minute to accommodate the increased workload. The heart may undergo mild hypertrophy, and blood pressure decreases slightly due to progesterone-induced vasodilation.

Why do pregnant women experience urinary frequency?

Urinary frequency is caused by increased glomerular filtration rate (due to higher blood volume) and the pressure from the enlarging uterus on the bladder. These factors lead to more frequent urination during pregnancy.

How does the respiratory system change during pregnancy?

The diaphragm is pushed upward by the enlarging uterus, making breathing more difficult. However, progesterone relaxes the thoracic ligaments, increasing the ribcage's diameter and helping maintain adequate tidal and minute volumes, leading to mild respiratory alkalosis, which aids oxygen exchange for the fetus.

What causes gastrointestinal issues like constipation and heartburn in pregnancy?

Hormonal changes, particularly the relaxation effect of progesterone on smooth muscles, slow down peristalsis, leading to constipation and bloating. The relaxation of the lower esophageal sphincter can result in gastric reflux and heartburn.

What is the hypercoagulable state during pregnancy and why is it important?

Pregnancy induces a hypercoagulable state due to elevated estrogen levels, which increase plasma fibrinogen, coagulation factors, and platelet aggregation while reducing antithrombin 3 activity. This prepares the body for the blood loss during delivery but also increases the risk of venous thromboembolism.