Female Pregnancy Overview

Female Pregnancy Overview

• Pregnancy involves complex hormonal and physiological changes throughout various stages.
• Key hormones like hCG, estrogen, progesterone, and placental lactogen (hPL) play crucial roles throughout pregnancy, affecting uterine structure, blood flow, metabolic shifts, and lactation.
• Fetal adrenal hormones like DHEA and cortisol are vital for the timing of labor.

Early Pregnancy (Luteal Phase)

• Fertilization occurs in the fallopian tubes early in the luteal phase.
• Progesterone secreted during this phase promotes nutrient secretion for embryo nourishment.
• Implantation of the embryo into the uterine wall occurs around day seven.
• The uterine wall, the decidua, develops around the embryo, ultimately becoming the placenta. This placental tissue includes villi and trophoblast cells.

Placenta Structure and Function

• The placenta facilitates nutrient exchange between mother and fetus.
• Fetal capillaries and maternal blood in the placental villi facilitate oxygen, nutrient, and waste exchange crucial for fetal development.
• Trophoblast cells within the placenta act as transporters and regulators of substances, supporting metabolic processes essential for the fetus.

Uterine Changes

• Estrogen and progesterone influence the uterine wall throughout pregnancy.
• Estrogen promotes proliferation of the endometrium, increasing uterine thickness.
• Progesterone decreases uterine contractility, maintaining uterine quiescence.
• The uterine muscular layer (myometrium) also undergoes proliferation, essential for labor. Increased vascular growth enhances blood flow to the placenta.

Key Placental Hormones

• hCG: A hormone crucial for early pregnancy, stimulating the corpus luteum to produce estrogen and progesterone. Low levels can lead to pregnancy loss.
• Placental Shift: Around weeks 8-12, the placenta begins producing its own estrogen and progesterone, taking over from the corpus luteum.
• hPL: Similar to prolactin and growth hormone, impacting breast development and glucose metabolism.

Physiological Changes During Pregnancy

• Brain-Pituitary-Gonadal Axis: Estrogen and progesterone from the placenta inhibit LH and FSH, preventing ovulation. Progesterone elevates body temperature.
• Food Intake: Increased hunger and metabolic demand are common.
• Mammary Gland Changes: Ductal growth occurs at puberty, and lobular-alveolar growth starts during the first trimester, stimulated by hormones.
• Cardiovascular System: Increased blood volume (about 40%), cardiac output, and uterine blood flow. Despite increased volume, blood pressure tends to decrease during normal pregnancy. Gestational hypertension is an abnormal increase.
• Metabolic Changes: Elevated glucose (due to insulin resistance), higher insulin levels, and fat deposition support fetal development. Gestational diabetes can result from excessive insulin resistance.

Labor and Delivery

• Estrogen's Role: Stimulates myometrial contractions, impacting oxytocin and prostaglandin effectiveness.
• Prostaglandin PGF2 alpha: Another hormone contributing to uterine contractions.
• Oxytocin's Role: Uterine contractions trigger oxytocin release, creating a positive feedback loop until delivery.

Control of Parturition (Birth)

• Estrogen/Progesterone Balance: The shift towards higher estrogen levels initiates labor.
• Fetal Role: Fetal adrenal hormones (particularly DHEA) contribute to increasing maternal estrogen levels, ultimately triggering labor.

Lactation

• Suckling: Stimulates prolactin and oxytocin release, essential for milk production and ejection.
• Prolactin: Increases milk protein production.
• Oxytocin: Ejects milk via myoepithelial cells.
• Colostrum: Early milk is lower in protein but rich in antibodies and glucose.

Pregnancy Summary

• Each stage of pregnancy (early, mid-late) involves unique sets of hormones, physiological changes, and associated functions.
• The placenta is a crucial interface for nutrient and gas exchange and hormone production.
• Labor and delivery are initiated and regulated by an intricate balance of hormones and fetal signals.
• Lactation follows delivery, and involves a complex neuroendocrine reflex.