Chapter 42 “Obstetrics” Personal Notes
Anatomy and Physiology Review
➢ The process is that the follicle goes through and the actual release of the oocyte (ovulation) are stimulated
by the release of specific hormones at appropriate times.
➢ An oocyte matures when the corresponding follicular cells respond to follicle stimulating hormones (FSH)
release the anterior pituitary gland, after the pituitary is first stimulated by the release of gonadotropin-
releasing factor (GnRF) from the hypothalamus.
➢ As the pre-ovulatory phase of the menstrual cycle progresses, the anterior pituitary gland releases
luteinizing hormone (LH), which stimulates the release of the egg (ovum).
➢ What is left of the follicle after the egg has been released becomes corpus luteum which intern secretes,
estrogen, progesterone, and inhibin.
➢ All three of these hormones, inhibit secretion of FSH from the anterior pituitary gland, thereby preventing
further development of follicles.
➢ At the end of pregnancy, the uterus and the placenta produce prostaglandins, they have hormone effects
and along with oxytocin, signal the uterus to contract, thereby beginning the process of labor.
➢ If the ovum is not fertilized, it dies and is reabsorbed with an approximately 36 to 48 hours of being
released.
➢ This initiates hormone signals that will lead to shedding of the endometrium as menstrual flow on about
the 28th day of the cycle or about 14 days after ovulation.
➢ If an egg is fertilized, hormonal triggers caused the glands of the endometrium to thicken and secrete
materials on which the egg will implant and grow.
➢ The uterus consist of three layers of muscle fibers: the perimetrium (outer protective layer), the
myometrium (middle layer), and the endometrium (inner lining).
➢ If the vagina is unable to stretch far enough, the tissues in and around the perineum may tear, causing
significant pain and bleeding.
➢ In the prehospital setting, you are limited to provide gentle pressure against the perineum to support the
tissues as they expand in response to the forces exerted by the fetal head as it presents.
➢ The mammary gland are modified sweat glands that are mainly composed of adipose tissue.
➢ Their primary purpose is lactation or milk secretion to provide nourishment to the newborn.
➢ Breast enlargement, tenderness, and milk excretion are all signs that a woman may be pregnant.
Conception and Fetal Development
➢ Once an egg has been fertilized and implanted in the endometrium of the uterus, both the egg and the
pregnant women begin to undergo significant physiologic, hormonal, and chemical changes.
➢ On entering the uterus, the egg begins absorbing uterine fluid through the cell membrane.
➢ As the fluid fill the eggs interior, cell division increases rapidly.
➢ The cells multiply on the outside of the egg surface, forming layers that will eventually generate the fetal
membrane, placenta, and embryo.
➢ The egg, now called a blastocyte, migrates to the endometrial wall and becomes implanted there
approximately one week after conception.
➢ The mass of cells of the blastocyte develops into the fetus, part of the outer blastocyte layer develops into
the placenta and the fetal membranes.
➢ Occasionally, the mechanism of implantation may result in vaginal bleeding that is spotty and painless, but
concern to the patient who may be aware that she is pregnant.
, ➢ Corpus luteum then begins to produce hormone designed to support the pregnancy until the placenta is
sufficiently developed to assume this function.
➢ The developing placenta produces projections that tap into the external tissue layer of the blastocyte,
where spaces called lacunae form.
➢ These spaces are filled with maternal blood.
➢ The connection from the placenta to the blastocyte allows both the embryo to draw on maternal circulation
for oxygenation and nutrition and embryonic waste products to be shunted safely away, it serves as a
beginning of the umbilical cord.
➢ The organogenesis period, which occurs during weeks 3 to 8 of gestation, is a critical development period
for the embryo. Teratogenic agents (drugs, chemicals, or other substances that are potentially harmful to
the developing babies) are more likely to cause significant damage during this period. Congenital
malformations that arise during organogenesis may lead to spontaneous abortion if they are severe and
incompatible with life.
➢ The placenta carries out several crucial functions during pregnancy, it serves as an early liver for the
developing fetus, taking care of the synthesis of glycogen and cholesterol, metabolizes fatty acids
produces antibodies that protect the fetus
➢ Placenta also provides the following functions:
o Respiratory gas exchange
o Transport of nutrients
o Excretion of waste
o Transfer of heat from the woman to the fetus
o Hormone production
o Formation of a barrier against harmful substances in the pregnant woman circulation.
➢ The fetal circulation differs from the circulation of the pregnant woman.
➢ The umbilical vein carries oxygenated blood from the placenta to the fetus.
➢ Umbilical arteries carry arteriovenous blood to the placenta.
➢ The fetus obtains its oxygen via the placenta, fetal circulation, largely bypasses the lungs until birth.
➢ Amniotic sac is a membranous bag that encloses the fetus in a watery fluid called amniotic fluid.
o Approximately 500 to 1000mL at term.
➢ Amniotic fluid provides the fetus with a weightless environment in which to develop.
➢ The gestational period is the time it takes for the fetus to develop in utero.
➢ The due date can be calculated by identifying the first day of the last cycle, adding one year, subtracting
three months, and adding seven days.
Physiologic Maternal Changes During Pregnancy
➢ Many of these changes can alter the bodies usual response to trauma or exacerbate underlying medical
conditions that can threaten the health of both the woman and the fetus.
➢ The rapidly changing internal environment, put stress on the woman.
➢ In addition, metabolic demands increased during pregnancy, and enlarging uterus with its significant
vascularity creates mechanical changes.
➢ After pregnancy has stretched the uterus, it will rarely return to its previous dimensions.
➢ Measurement of the fundus of the uterus (the top portion, opposite the cervix) can identify possible
developmental problems.
➢ The length increases by approximately 1 cm for every week of gestation.
, ➢ If the length does not match the expected value, it could indicate uterine growth problems or breach
position (if shorter) or the possibility of twins (if longer).
➢ As pregnancy continues, the uterus enlarges and increases in weight.
➢ This weight place is pressure on the lower end of the intestine and the women’s rectum and often results in
constipation.
➢ The smooth muscles in the gastrointestinal tract relax due to increased progesterone levels, which causes
a decrease in GI motility, decrease motility sometimes can also cause heartburn and burping.
➢ The pregnant patient is at higher risk of vomiting during an emergency, potentially resulting in airway
compromise.
➢ The kidneys increase in size and volume.
➢ Right ureter also increases in diameter being more dilated than the left side in most cases.
➢ These changes results in an increased chance of urinary tract infection if the pregnant woman does not
empty her bladder frequently.
➢ The average woman has approximately 8.5 to 10.5 pints of blood available as total circulating volume.
➢ Blood volume increases by about 30% to 50% during pregnancy, increasing rapidly during the first half of
pregnancy, and then stabilizing or decreasing slightly by term.
➢ The increase in the level of blood volume depends on such factors as patient size, single versus multiple
gestation, gravidity (the total number of times a woman has been pregnant regardless of those pregnancies
outcomes, including the current pregnancy), and parity (the number of live births).
➢ A greater blood volume is needed to meet the metabolic needs of the developing fetus, to adequately
profuse maternal organs (the uterus and the kidneys), and to help compensate for blood loss during
delivery.
➢ During vaginal delivery, a woman may lose as much as 500mL of blood.
➢ The uterus, as it contracts, tends to shunt blood back into the maternal circulation, thereby preserving
maternal circulatory hemostasis.
➢ The increase in RBCS the pregnant woman’s need for iron, which is why most women take prenatal
vitamins.
➢ The woman does not take iron supplements, the fetus will deplete the maternal stores to meet its own
needs for iron, resulting in anemia for the woman, and possibly resulting in preterm labor and spontaneous
abortion.
➢ A woman’s white blood cell count also increases during pregnancy without an infection present.
➢ Levels of clotting factors similarly increase, as the concentrations of fibrinogen.
➢ The size of the pregnant women’s heart increases slightly to the increased cardiac workload during
pregnancy.
➢ As the uterus enlarges and the diaphragm becomes elevated, the internal maternal organs begin to shift
their positions in the abdomen to make room.
➢ Systolic and diastolic murmurs are common.
➢ Heart rate gradually increases by an average of 15 to 20 bpm by term.
➢ Changes that can occur during pregnancy can be seen on an ECG, may include ectopic beats and SVT.
Other changes include a slight left-axis deviation and lead III changes such as a low-voltage QRS complex,
T-wave inversion or flattening, occasional Q waves.
➢ Synchronize cardioversion may be required if SVT or ventricular tachycardia causes hemodynamic
instability.
➢ After 20 weeks gestation, resting or lying supine, can cause the weight of the uterus to compress the
inferior vena cava, thereby decreasing venous return to the heart.
Anatomy and Physiology Review
➢ The process is that the follicle goes through and the actual release of the oocyte (ovulation) are stimulated
by the release of specific hormones at appropriate times.
➢ An oocyte matures when the corresponding follicular cells respond to follicle stimulating hormones (FSH)
release the anterior pituitary gland, after the pituitary is first stimulated by the release of gonadotropin-
releasing factor (GnRF) from the hypothalamus.
➢ As the pre-ovulatory phase of the menstrual cycle progresses, the anterior pituitary gland releases
luteinizing hormone (LH), which stimulates the release of the egg (ovum).
➢ What is left of the follicle after the egg has been released becomes corpus luteum which intern secretes,
estrogen, progesterone, and inhibin.
➢ All three of these hormones, inhibit secretion of FSH from the anterior pituitary gland, thereby preventing
further development of follicles.
➢ At the end of pregnancy, the uterus and the placenta produce prostaglandins, they have hormone effects
and along with oxytocin, signal the uterus to contract, thereby beginning the process of labor.
➢ If the ovum is not fertilized, it dies and is reabsorbed with an approximately 36 to 48 hours of being
released.
➢ This initiates hormone signals that will lead to shedding of the endometrium as menstrual flow on about
the 28th day of the cycle or about 14 days after ovulation.
➢ If an egg is fertilized, hormonal triggers caused the glands of the endometrium to thicken and secrete
materials on which the egg will implant and grow.
➢ The uterus consist of three layers of muscle fibers: the perimetrium (outer protective layer), the
myometrium (middle layer), and the endometrium (inner lining).
➢ If the vagina is unable to stretch far enough, the tissues in and around the perineum may tear, causing
significant pain and bleeding.
➢ In the prehospital setting, you are limited to provide gentle pressure against the perineum to support the
tissues as they expand in response to the forces exerted by the fetal head as it presents.
➢ The mammary gland are modified sweat glands that are mainly composed of adipose tissue.
➢ Their primary purpose is lactation or milk secretion to provide nourishment to the newborn.
➢ Breast enlargement, tenderness, and milk excretion are all signs that a woman may be pregnant.
Conception and Fetal Development
➢ Once an egg has been fertilized and implanted in the endometrium of the uterus, both the egg and the
pregnant women begin to undergo significant physiologic, hormonal, and chemical changes.
➢ On entering the uterus, the egg begins absorbing uterine fluid through the cell membrane.
➢ As the fluid fill the eggs interior, cell division increases rapidly.
➢ The cells multiply on the outside of the egg surface, forming layers that will eventually generate the fetal
membrane, placenta, and embryo.
➢ The egg, now called a blastocyte, migrates to the endometrial wall and becomes implanted there
approximately one week after conception.
➢ The mass of cells of the blastocyte develops into the fetus, part of the outer blastocyte layer develops into
the placenta and the fetal membranes.
➢ Occasionally, the mechanism of implantation may result in vaginal bleeding that is spotty and painless, but
concern to the patient who may be aware that she is pregnant.
, ➢ Corpus luteum then begins to produce hormone designed to support the pregnancy until the placenta is
sufficiently developed to assume this function.
➢ The developing placenta produces projections that tap into the external tissue layer of the blastocyte,
where spaces called lacunae form.
➢ These spaces are filled with maternal blood.
➢ The connection from the placenta to the blastocyte allows both the embryo to draw on maternal circulation
for oxygenation and nutrition and embryonic waste products to be shunted safely away, it serves as a
beginning of the umbilical cord.
➢ The organogenesis period, which occurs during weeks 3 to 8 of gestation, is a critical development period
for the embryo. Teratogenic agents (drugs, chemicals, or other substances that are potentially harmful to
the developing babies) are more likely to cause significant damage during this period. Congenital
malformations that arise during organogenesis may lead to spontaneous abortion if they are severe and
incompatible with life.
➢ The placenta carries out several crucial functions during pregnancy, it serves as an early liver for the
developing fetus, taking care of the synthesis of glycogen and cholesterol, metabolizes fatty acids
produces antibodies that protect the fetus
➢ Placenta also provides the following functions:
o Respiratory gas exchange
o Transport of nutrients
o Excretion of waste
o Transfer of heat from the woman to the fetus
o Hormone production
o Formation of a barrier against harmful substances in the pregnant woman circulation.
➢ The fetal circulation differs from the circulation of the pregnant woman.
➢ The umbilical vein carries oxygenated blood from the placenta to the fetus.
➢ Umbilical arteries carry arteriovenous blood to the placenta.
➢ The fetus obtains its oxygen via the placenta, fetal circulation, largely bypasses the lungs until birth.
➢ Amniotic sac is a membranous bag that encloses the fetus in a watery fluid called amniotic fluid.
o Approximately 500 to 1000mL at term.
➢ Amniotic fluid provides the fetus with a weightless environment in which to develop.
➢ The gestational period is the time it takes for the fetus to develop in utero.
➢ The due date can be calculated by identifying the first day of the last cycle, adding one year, subtracting
three months, and adding seven days.
Physiologic Maternal Changes During Pregnancy
➢ Many of these changes can alter the bodies usual response to trauma or exacerbate underlying medical
conditions that can threaten the health of both the woman and the fetus.
➢ The rapidly changing internal environment, put stress on the woman.
➢ In addition, metabolic demands increased during pregnancy, and enlarging uterus with its significant
vascularity creates mechanical changes.
➢ After pregnancy has stretched the uterus, it will rarely return to its previous dimensions.
➢ Measurement of the fundus of the uterus (the top portion, opposite the cervix) can identify possible
developmental problems.
➢ The length increases by approximately 1 cm for every week of gestation.
, ➢ If the length does not match the expected value, it could indicate uterine growth problems or breach
position (if shorter) or the possibility of twins (if longer).
➢ As pregnancy continues, the uterus enlarges and increases in weight.
➢ This weight place is pressure on the lower end of the intestine and the women’s rectum and often results in
constipation.
➢ The smooth muscles in the gastrointestinal tract relax due to increased progesterone levels, which causes
a decrease in GI motility, decrease motility sometimes can also cause heartburn and burping.
➢ The pregnant patient is at higher risk of vomiting during an emergency, potentially resulting in airway
compromise.
➢ The kidneys increase in size and volume.
➢ Right ureter also increases in diameter being more dilated than the left side in most cases.
➢ These changes results in an increased chance of urinary tract infection if the pregnant woman does not
empty her bladder frequently.
➢ The average woman has approximately 8.5 to 10.5 pints of blood available as total circulating volume.
➢ Blood volume increases by about 30% to 50% during pregnancy, increasing rapidly during the first half of
pregnancy, and then stabilizing or decreasing slightly by term.
➢ The increase in the level of blood volume depends on such factors as patient size, single versus multiple
gestation, gravidity (the total number of times a woman has been pregnant regardless of those pregnancies
outcomes, including the current pregnancy), and parity (the number of live births).
➢ A greater blood volume is needed to meet the metabolic needs of the developing fetus, to adequately
profuse maternal organs (the uterus and the kidneys), and to help compensate for blood loss during
delivery.
➢ During vaginal delivery, a woman may lose as much as 500mL of blood.
➢ The uterus, as it contracts, tends to shunt blood back into the maternal circulation, thereby preserving
maternal circulatory hemostasis.
➢ The increase in RBCS the pregnant woman’s need for iron, which is why most women take prenatal
vitamins.
➢ The woman does not take iron supplements, the fetus will deplete the maternal stores to meet its own
needs for iron, resulting in anemia for the woman, and possibly resulting in preterm labor and spontaneous
abortion.
➢ A woman’s white blood cell count also increases during pregnancy without an infection present.
➢ Levels of clotting factors similarly increase, as the concentrations of fibrinogen.
➢ The size of the pregnant women’s heart increases slightly to the increased cardiac workload during
pregnancy.
➢ As the uterus enlarges and the diaphragm becomes elevated, the internal maternal organs begin to shift
their positions in the abdomen to make room.
➢ Systolic and diastolic murmurs are common.
➢ Heart rate gradually increases by an average of 15 to 20 bpm by term.
➢ Changes that can occur during pregnancy can be seen on an ECG, may include ectopic beats and SVT.
Other changes include a slight left-axis deviation and lead III changes such as a low-voltage QRS complex,
T-wave inversion or flattening, occasional Q waves.
➢ Synchronize cardioversion may be required if SVT or ventricular tachycardia causes hemodynamic
instability.
➢ After 20 weeks gestation, resting or lying supine, can cause the weight of the uterus to compress the
inferior vena cava, thereby decreasing venous return to the heart.
