Pregnancy and Menopause Terminology

Fertilization

  • Fertilization is the fusion of male and female nuclei.

Cell Division

  • Following fertilization, the zygote undergoes cell division.

Implantation

  • Approximately 7 days post-fertilization, the blastocyst burrows into the uterine wall.

Placenta

  • The placenta facilitates the exchange of nutrients and waste between the mother and fetus.
  • Maternal blood is separated from fetal blood by the chorion.
  • Terminology:
    • Zygote: Formed once male and female nuclei combine.
    • Blastocyst: The stage during the first 2 weeks.
    • Embryo: From 2 to 8 weeks.
    • Fetus: From week 9 to birth.
    • Length of Pregnancy: Approximately 40 weeks.

Pregnancy Hormones

  • Human Chorionic Gonadotropin (hCG):
    • Secreted by the blastocyst and placenta.
    • Its presence in urine indicates pregnancy.
    • Stimulates the growth of the corpus luteum, doubling its size.
    • Leads to increased amounts of estrogen and progesterone.
  • Relaxin:
    • Secreted by the corpus luteum and placenta.
    • Relaxes the ligaments of the body.
  • Placenta:
    • Secretes estrogen, which increases water retention and protein synthesis.
    • Secretes progesterone, which causes smooth muscle relaxation and raises body temperature.
  • After 3 months, the corpus luteum is no longer needed.
    • The placenta serves as a point of exchange between the fetus and mother.
    • The placenta functions as an endocrine gland, secreting hormones to maintain pregnancy.
    • Increased levels of estrogen and progesterone are observed during pregnancy.

Physiological Changes During Pregnancy

  • Rationale for Physiological Adaptation:
    • To provide a suitable environment for the growth, nutrition, and development of the fetus.
    • To protect and prepare the mother for the process of pregnancy and support for the newborn.

Maternal Cardiovascular Alterations

  • Blood Volume:
    • Increases by 45-50%.
    • Accommodates increased blood flow to the uterus and other organs.
  • Heart Rate:
    • Increases by 15-25% (approximately 15 bpm) at rest.
  • Stroke Volume:
    • Increases by 30%.
    • Caused by the increase in plasma volume and increased venous return.
  • Cardiac Output:
    • Increases by 40-50% (approximately 1.5 L).
    • Caused by increases in stroke volume and heart rate.
  • Blood Pressure:
    • Can decrease or stay the same in the 1st and 2nd Trimesters, returning to normal by the 3rd.
  • Peripheral Resistance:
    • Increased progesterone causes vasodilation, which decreases resistance to flow.
    • Helps contribute to reduced blood pressure.
  • Supine Hypotension Syndrome:
    • Blood pressure falls when lying supine as the uterus compresses the inferior vena cava, therefore decreasing venous return.
    • Especially when the mother is lying in a supine position, particularly on the left side.
  • Cardiac Position and Size:
    • The diaphragm is pushed upwards.
    • The apex of the heart is pushed upwards and laterally.
    • The heart enlarges by 70-80 mL.
    • Increased venous filling is caused by an increase in plasma volume.
  • Primary objective of adaptations is to increase oxygen supply in order to accommodate both fetus and mother.

Maternal Respiratory Alterations

  • Oxygen demand increases.
  • Increases in:
    • Tidal volume (30-50%)
    • Inspiratory capacity
    • Minute volume (20-50%)
    • Oxygen consumption (absolute)
  • No performance benefit due to increased ventilation (over-breathing).
  • Decreases in:
    • Expiratory reserve volume
    • Residual volume
    • Displacement of the diaphragm superiorly
    • Airway resistance
  • These increases and corresponding decreases all assist with more efficient gas mixing.

Maternal Renal Alterations

  • As a result of increased plasma volume:
    • Kidney volume enlarges
  • Increases in:
    • Renal blood flow (30-50%)
    • Glomerular filtration rate (50%)
  • Increased urination.
  • Evidence of glucosuria during pregnancy (possibly due to less efficient tubular reabsorption).
    • Not an indication of diabetes.

Thermoregulation

  • During pregnancy, the metabolic rate increases, leading to an increase in heat production.
  • The body dissipates additional heat load through:
    • Increase in ventilation
    • Increase in skin blood flow
  • Considerations:
    • Keep hydrated
    • Avoid high environmental temperatures

Maternal Endocrine Changes

  • Anterior Pituitary:
    • Increased plasma concentrations of Prolactin
    • Placenta produces CRH and ACTH
    • GH, LH, FSH are suppressed
  • Posterior Pituitary:
    • Increased number of oxytocin receptors
  • Thyroid function increases

Physical Changes

  • Increased:
    • Weight gain to the anterior
    • Ligament Laxity (Relaxin)
    • Joint mobility (hypermobility)
    • The center of Gravity moves forward
    • Increased weight of uterus and breasts
    • Increased loading of joints

Pelvic Floor

  • Layer of muscles which support the pelvic organs (Uterus, Bladder, Bowel).
    • Muscles can weaken, leading to urinary incontinence or organ prolapse.

Menopause

  • Cessation of the menstrual cycle.
  • When: 40-60 years of age.
  • Why:
    • Remaining number of follicles is small.
    • Follicles left are less sensitive to FSH and LH.
    • Reduced amounts of estrogen and progesterone.
  • Symptoms:
    • Uncomfortable sweating (hot flushes).
    • Anxiety.
    • Fatigue.
    • Emotional disturbances.

Clinical Perspective

  • Post-menopausal Osteoporosis:
    • 1 in 3 women.
    • Reduction in bone mineral density due to hormonal factors.
    • Reduced estrogen = increased bone loss.
    • Increased risk of fractures.