Physiology of Pregnancy

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Questions and Answers

What change occurs to the cardiac output (COP) during the last 8 weeks of pregnancy?

It remains at normal levels.

It falls to only a little above normal levels. (correct)

It decreases below normal levels.

It significantly increases above normal levels.

By how much does maternal blood volume increase during pregnancy?

About 30% (correct)

Exactly 50%

Over 40%

Approximately 20%

What is one factor that may explain the variability in cardiac output during late pregnancy?

Hormonal changes in early pregnancy.

Increased fetal activity.

Unexplained reasons. (correct)

Maternal age.

When does the change in cardiac output to slightly above normal occur during pregnancy?

In the last 8 weeks of pregnancy. Signup and view all the answers

What can be inferred about the relationship between maternal blood volume and pregnancy?

It increases approximately 30% above normal levels. Signup and view all the answers

How does high levels of progesterone affect the respiratory center?

It increases sensitivity to CO2. Signup and view all the answers

At what stage of pregnancy is human chorionic somatomammotropin (HPL) secreted by the placenta?

5th week Signup and view all the answers

What physical change occurs due to the growing uterus related to the abdominal contents?

It presses upward against the abdominal contents. Signup and view all the answers

Which hormone is primarily associated with the function of human chorionic somatomammotropin (HPL) during pregnancy?

Insulin Signup and view all the answers

Which of the following statements is true regarding progesterone's effects?

It enhances the respiratory center's reaction to CO2 levels. Signup and view all the answers

What is the primary source of human chorionic somatomammotropin (HPL) in a pregnant woman?

Placenta Signup and view all the answers

Which of the following statements regarding the secretion of human chorionic somatomammotropin (HPL) is false?

HPL secretion increases significantly after the first trimester. Signup and view all the answers

What is a consequence of the uterus pressing against abdominal contents?

It causes displacement of other organs within the abdomen. Signup and view all the answers

Increased sensitivity of the respiratory center due to high progesterone can lead to which of the following physiological effects?

Increased respiratory rate. Signup and view all the answers

Which physiological process is NOT influenced by human chorionic somatomammotropin (HPL)?

Skeletal muscle growth Signup and view all the answers

What is the primary source of progesterone during the early stages of pregnancy?

The corpus luteum Signup and view all the answers

What physiological changes does progesterone induce in the uterine endometrium?

Causes decidual cells to develop Signup and view all the answers

How does the secretion of progesterone change as pregnancy progresses?

It increases tremendously after the early stages Signup and view all the answers

What is the role of Human Chorionic Gonadotropin (hCG) in relation to thyroid hormone levels?

It stimulates an increase in thyroid hormones. Signup and view all the answers

When does the concentration of hCG typically reach its maximum during pregnancy?

10 to 12 weeks after ovulation Signup and view all the answers

Which statement correctly describes progesterone's role during pregnancy?

It acts to prepare the endometrium for implantation. Signup and view all the answers

What is the relationship between the corpus luteum and placenta regarding progesterone secretion?

The placenta eventually takes over progesterone secretion from the corpus luteum. Signup and view all the answers

How does parathyroid hormone (PTH) affect calcium levels in the mother during pregnancy?

It mobilizes calcium from the mother's bones. Signup and view all the answers

Which hormones are produced by the placenta?

Estrogen and progesterone Signup and view all the answers

What physiological structure secretes Human Chorionic Gonadotropin during early pregnancy?

The syncytial trophoblast Signup and view all the answers

What is the primary role of progesterone produced by the placenta?

Maintaining the uterine lining Signup and view all the answers

What happens to hCG levels after reaching their peak during the first trimester?

They decrease to a lower value by 16 to 20 weeks. Signup and view all the answers

Which hormone is NOT typically produced by the placenta?

FSH Signup and view all the answers

Which of the following statements about placental hormones is correct?

Placental hormones regulate various functions throughout pregnancy. Signup and view all the answers

Which hormone is primarily responsible for preparing the breast tissue for lactation?

Prolactin Signup and view all the answers

What is the primary physiological process through which fluid is formed and absorbed during pregnancy?

Direct absorption via amniotic membranes Signup and view all the answers

Which gland primarily regulates fluid absorption in relation to pregnancy hormones?

Pituitary gland Signup and view all the answers

Which factor could potentially disrupt fluid absorption through amniotic membranes during pregnancy?

Hormonal imbalances Signup and view all the answers

What role does the amniotic membrane play in fetal development?

It acts as a barrier to infections Signup and view all the answers

Which physiological condition would most likely affect hormonal factors during pregnancy?

Thyroid dysfunction Signup and view all the answers

Which hormones are specifically produced by the placenta during pregnancy?

Estrogen and progesterone Signup and view all the answers

What is one of the roles of the substance mentioned that softens the cervix during delivery?

It acts as a vasodilator, increasing blood flow. Signup and view all the answers

Which of the following combinations represents hormones associated with the placenta?

Human chorionic gonadotropin and progesterone Signup and view all the answers

How does the substance softening the cervix affect other physiological parameters in pregnancy?

It contributes to increased venous return and cardiac output. Signup and view all the answers

What functions does progesterone serve during pregnancy?

Preparing the uterine lining for implantation Signup and view all the answers

Which of the following does NOT describe a role of the substance that softens the cervix during labor?

Lowers respiratory rate. Signup and view all the answers

Which hormones function collaboratively during the later stages of pregnancy?

Human chorionic somatomammotropin and progesterone Signup and view all the answers

In regard to hormonal secretion, which statement is accurate concerning the placenta?

It produces hormones that modulate the maternal immune response. Signup and view all the answers

In what way does the softening of the cervix during delivery relate to blood flow?

It is thought to enhance blood flow to various tissue types. Signup and view all the answers

What physiological change is associated with the substance that serves as a vasodilator during pregnancy?

Enhanced renal perfusion. Signup and view all the answers

What is the typical range of weight gain for a pregnant woman?

11 to 16 kg Signup and view all the answers

During which trimesters does most of the weight gain in pregnancy occur?

Last two trimesters Signup and view all the answers

What percentage of total weight gain is typically attributed to the last two trimesters?

Around 75% or more Signup and view all the answers

Which factor primarily influences the timing of significant weight gain during pregnancy?

Fetal development stages Signup and view all the answers

What is the expected weight gain pattern for a pregnant woman throughout her pregnancy?

Slow gain in first trimester, rapid in last two trimesters Signup and view all the answers

Which hormone primarily influences the modulation of maternal immune response during pregnancy?

Progesterone Signup and view all the answers

What is the principal mechanism of increased tidal volume observed during late pregnancy?

Increased progesterone levels Signup and view all the answers

How does human chorionic somatomammotropin (HPL) contribute to maternal metabolism?

By promoting lipolysis and reducing insulin sensitivity Signup and view all the answers

Which physiological change is primarily driven by the increased blood volume during pregnancy?

Increased preload and stroke volume Signup and view all the answers

What physiological role does the corpus luteum fulfill during the early stages of pregnancy?

Produces progesterone to maintain the uterine lining Signup and view all the answers

What is the primary effect of human chorionic gonadotropin (hCG) during early pregnancy?

To preserve the corpus luteum for hormone secretion Signup and view all the answers

Which cells are stimulated by hCG in a male fetus to produce testosterone?

Leydig cells Signup and view all the answers

What role does hCG play in relation to hormone secretion during early pregnancy?

It promotes the production of progesterone and estrogen from the corpus luteum Signup and view all the answers

For how long does hCG maintain the secretion of progesterone and estrogen?

Typically for the first few months of pregnancy Signup and view all the answers

Which hormone is primarily responsible for stimulating testosterone production in the male fetus until birth?

Human chorionic gonadotropin (hCG) Signup and view all the answers

Study Notes

Maternal Response to Pregnancy

Pregnancy increases the size of sexual organs due to hormone levels.
Pregnant women may experience physical changes like edema, acne, or masculine/acromegalic features.
Weight gain during pregnancy is approximately 11-16 kg.
Most of this gain is in the last two trimesters.
Roughly 4 kg is the fetus, and approximately 1.5 kg is amniotic fluid, placenta, and fetal membranes.
The uterus increases by about 1 kg, and breasts increase by another 1 kg.
About 2 kg is extra fluid in the blood and extracellular fluid, which often leaves the body after birth.
The remaining 1-8 kg is typically fat accumulation.

Metabolism During Pregnancy

Increased thyroxine, adrenocortical hormones, and sex hormones in pregnancy increase basal metabolic rate.
Basal metabolic rate (BMR) increases by roughly 15% in the second half of pregnancy.
Pregnant women may experience feelings of overheating due to the increased load they carry.
Extra energy is needed for muscle activity to support pregnancy.

Changes in the Maternal Circulatory System During Pregnancy

Blood flow through the placenta increases.
Peripheral resistance decreases.
Cardiac output increases by 30-40% in the 27th week of pregnancy.
Cardiac output falls slightly below the rate of a non-pregnant woman during the last 8 weeks.

Maternal Blood Volume During Pregnancy

Maternal blood volume increases by about 30%.
Increased fluid retention is due to aldosterone and estrogen.
At birth, the body holds 1-2 liters of extra blood volume.
Roughly 1/4 of this volume is lost during delivery.

Maternal Respiration During Pregnancy

Minute ventilation is increased in pregnancy due to greater size and increased BMR.
High levels of progesterone increase respiratory center sensitivity to CO2.
The growing uterus puts pressure on the abdomen.

Changes in Lung Volumes During Pregnancy

Functional residual capacity decreases due to reduced expiratory and residual volumes.
Increased displacement of the diaphragm.
Tidal volume increases by 40%, leading to hyperventilation and hypocapnia.

Maternal Kidney Function During Pregnancy

Urine production rate is slightly elevated due to increased fluid intake and excretory products.
Renal tubules increase reabsorptive capacity due to hormones.
Renal blood flow and glomerular filtration rate increases.
This likely compensates for increased reabsorption of water and salt.
Pregnant women usually retain reasonable amounts of extra water and salt.

Amniotic Fluid and Its Formation

Amniotic fluid volume is about 0.5-1 liter.
Derived from renal excretion, fetal excretion, and absorption from gastrointestinal and pulmonary tracts.

Hormonal Factors in Pregnancy

(Various hormones are listed with their effects and the gland of origin.)

Activities of Other End Glands

Anterior pituitary produces more ACTH, TSH, PRL. FSH and LH drop.
Adrenal cortex releases more cortisol (mobilizes amino acids), and aldosterone (water absorption). This can lead to increased blood pressure and edema.
Thyroid and parathyroid: Thyroid hormone is elevated by placental hCG. Parathyroid hormone releases calcium from the mother's bones.

Human Chorionic Gonadotropin (HCG)

Secreted in early pregnancy by the syncytiotrophoblast.
Peaks in early pregnancy, then declines.
Maintains corpus luteum function, which produces progesterone and estrogen.

Estrogen in Pregnancy

Secreted by the placenta and maternal adrenal glands (and fetuses' adrenal glands).
Causes enlargement of the uterus, breasts, and external genitalia.
Relaxes pelvic ligaments.

Secretion of Progesterone by the Placenta

Secreted by corpus luteum at the start of pregnancy, then extensively by the placenta.
Maintains the uterine lining (endometrium).
Prevents miscarriage, by decreasing uterine contractility.
Needed for nourishing the embryo in the early stages.
Prepares the breasts for lactation.

Human Chorionic Somatomammotropin (HPL)

Secreted by the placenta in later stages of pregnancy.
Promotes breast development.
Has growth hormone-like effects.
Decreases maternal insulin sensitivity and glucose utilization.
Promotes fatty acid release from fat stores.

"Relaxin"

Secreted by ovaries and placenta.
Softens the cervix for delivery.
Acts as a vasodilator. Increases blood flow, especially to the kidneys resulting in elevated COP.
Contributes to increased blood flow in various tissues during pregnancy.

Test Your Understanding

The placenta produces estrogen and progesterone.

Secretion of Estriol During Pregnancy

Depends on both a functioning fetus and placenta.

Question

Tidal volume (TV) increases during pregnancy.

References

(Sources for information are listed)

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Description

This quiz covers the physiological changes and hormonal responses that occur during pregnancy. Questions focus on cardiac output, blood volume, and various hormones such as human chorionic somatomammotropin (HPL) and progesterone. Test your understanding of these crucial adaptations in the body during pregnancy.