1: Patient Care
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2: Normal Obstetrics
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3: Abnormal Obstetrics
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4: General Gynecology
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7: Neoplasia
6 Topics
Maternal-Fetal Physiology
Duration = 10:18
00:00
 APGO educational topic number 8
00:01
maternal fetal physiology this is the
00:04
story of Peggy preggers and the
00:06
physiologic changes that occur in her
00:08
body throughout her pregnancy a lot
00:10
happens to the female body in order to
00:12
create a new human being the objectives
00:15
of this video to discuss the maternal
00:16
physiologic and anatomic changes
00:18
associated with pregnancy describe fetal
00:21
and placental physiology and lastly
00:23
interpret common diagnostic studies
00:25
during pregnancy there are a lot of
00:27
changes that occur in each of the three
00:29
trimesters of pregnancy remember that we
00:31
use menstrual dating when calculating
00:33
the weeks here is our trusty pregnancy
00:34
wheel and from the first day of her last
00:37
menstrual period we calculate the
00:38
estimated date of delivery or EDD as 40
00:41
weeks after the LMP so the first
00:44
trimester is approximately zero to
00:45
thirteen weeks the second trimester is
00:47
approximately 14 or 27 weeks and the
00:49
third trimester is approximately 28 to
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40 weeks we will discuss changes in the
00:53
pregnant body by system and how these
00:55
changes occur in the three different try
00:56
Buster’s there are changes in thyroid
00:58
regulation during pregnancy remember
01:01
that beta HCG levels peak at a hundred
01:04
thousand around ten weeks and then come
01:07
down to about ten thousand at term beta
01:12
HCG has thyrotropin like activity and
01:14
this stimulates maternal thyroxine or t4
01:17
secretion and thus produces a transient
01:19
rise in free t4 levels in the first
01:21
trimester as beta HCG levels decline
01:24
free t4 levels decline to normal
01:26
concentrations rising levels of estrogen
01:28
and pregnancy caused an increase in
01:30
thyroxine binding globulin which results
01:32
in increased levels of total t4 and
01:34
total t3 but levels of free t4 and free
01:38
t3 are unchanged from the normal range
01:40
let’s now move to the GI system here is
01:43
Peggy in her first trimester with her
01:45
small developing pregnancy and her
01:47
corpus luteum is making large volumes of
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progesterone as the pregnancy progresses
01:51
past the first trimester the placenta
01:53
will take over as the main source of
01:55
progesterone production progesterone
01:57
relaxes smooth muscles throughout the
01:59
body and in the GI system the
02:00
progesterone will relax the lower
02:02
esophageal sphincter tone which can
02:04
result in gastroesophageal reflux
02:06
disease or GERD progesterone also
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reduces gallbladder contractility which
02:10
leads to an increased prevalence of
02:12
gallstone
02:13
progesterone also decreases GI motility
02:16
which can cause constipation in the
02:18
first trimester many women experience
02:20
nausea and vomiting
02:21
the term morning sickness is not very
02:23
accurate for many women experience it
02:25
throughout the day approximately fifty
02:26
to ninety percent of women experience
02:28
nausea and vomiting in the first
02:29
trimester the cause is unknown but is
02:31
thought to be related to elevated levels
02:33
of progesterone and beta HCG severe
02:36
nausea and vomiting and pregnancy is
02:38
referred to as hyperemesis gravidarum
02:39
and can result in significant weight
02:41
loss Keeton emia and electrolyte
02:43
imbalance in the second trimester as the
02:46
beta HCG levels decline nausea and
02:48
vomiting tends to improve and for most
02:50
women it is abated by about 14 to 16
02:52
weeks as the uterus grows throughout the
02:54
second and third trimester the stomach
02:56
is physically displaced upwards by the
02:58
growing uterus and this also contributes
03:00
to GERD during pregnancy let’s move now
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to the cardiovascular system the female
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body essentially needs more volume to
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support the growing pregnancy the
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circulating blood volume begins
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increasing by week six eight and reaches
03:12
a peak increase of forty-five percent by
03:15
32 weeks the heart essentially needs to
03:18
work harder during pregnancy cardiac
03:20
output increases by 30 to 50 percent
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with 50 percent of that increase
03:24
occurring by eight weeks
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remember that cardiac output equals
03:28
heart rate times stroke volume in the
03:31
first half of pregnancy
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cardiac output increases are secondary
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to increase stroke volume in the second
03:37
half of pregnancy cardiac output
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increases are secondary to increased
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heart rate there is a decrease in blood
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pressure during pregnancy secondary to
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progesterone smooth muscle relaxing
03:46
effects and increase production of azo
03:48
dilatory substances from the growing
03:50
placenta supine postural hypotension
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syndrome refers to the hypotension that
03:55
pregnant women experience when laying
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flat on their backs late in pregnancy as
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the uterus grows it can impede the vena
04:01
cava
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when a woman is supine this is why we
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advise women not to lay flat on their
04:05
backs while sleeping and instead
04:07
recommend sleeping with a left tilt or
04:09
on their side and remember as a uterus
04:12
grows it gets more of cardiac output so
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by the end of pregnancy it gets 20% of
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cardiac output as opposed to 2% of
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cardiac output in the first trimester
04:20
moving on to the respiratory system
04:23
oxygen consumption increases during
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pregnancy
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minute ventilation which is defined as
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the volume of air that is taken in every
04:30
minute increases by 30 to 40 percent
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this increase in ventilation results in
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increased production of co2 which
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results in a reduction of arterial pco2
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or a development of a respiratory
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alkalosis this is balanced by the kidney
04:45
excreting more bicarbonate which yields
04:47
the lower bicarbonate levels seen in
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pregnancy an arterial blood gas in
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pregnancy will show a compensated
04:53
respiratory alkalosis with a normal pH
04:55
the maternal thorax undergoes several
04:57
morphological changes during pregnancy
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the diaphragm is elevated and impressive
05:02
four centimeters by late pregnancy due
05:04
to the gravity uterus in addition the
05:06
sub costal angle widens as the chest
05:08
diameter and circumference increased
05:10
slightly moving on to the hematologic
05:13
system remember that the circulating
05:14
volume increases by 45 to 50 percent by
05:17
the third trimester of pregnancy the red
05:19
cell volume also increases although to a
05:21
lesser extent than the plasma volume the
05:24
maternal blood volume increases by 35%
05:27
at term this creates a physiologic
05:29
anemia at term the average hemoglobin
05:32
concentration is 12.5 compared to 14 in
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the non pregnant State supplemental iron
05:37
during pregnancy is thus intended to
05:39
prevent further iron deficiency the
05:41
concentration of different clotting
05:43
factors change during pregnancy
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fibrinogen levels increased by 50%
05:47
protein C and protein s levels decrease
05:50
and the risk of thromboembolism doubles
05:52
during pregnancy and increases to 5.5
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times the normal risk during the
05:56
immediate postpartum time how do all of
05:59
these changes manifest on examination of
06:01
pecky preggers first expect to see low
06:04
blood pressures blood pressure start to
06:06
decline by week 7 and reach a maximal
06:08
decline by weeks 24 to 26 weeks it is
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also common to see distended neck veins
06:13
from the increased volume of pregnancy
06:15
pregnant women often also have a
06:17
low-grade systolic ejection murmur
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secondary to increase flow across the
06:20
aortic and pulmonic valves note a
06:23
diastolic murmur is not normal in
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pregnancy and should be evaluated let’s
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now switch gears and discuss fetal and
06:29
placental physiology here is a
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cross-section of the umbilical cord with
06:33
two umbilical arteries and one umbilical
06:35
vein
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remember that blood flows from the
06:38
umbilical vein
06:39
to the fetus and then from the fetus
06:42
through the two umbilical arteries so
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blood flows from the umbilical vein to
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the portal system and here 50% of the
06:54
blood goes to the right lobe of the
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liver and 50% of the blood goes through
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this first shunt to pregnancy called the
07:01
ductus venosus into the inferior vena
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cava
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here’s blood going through the ductus
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venosus into the inferior vena cava
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there the blood travels to the right
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atrium so here is the heart with the
07:17
right atrium the right ventricle the
07:21
left atrium and the left ventricle the
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second shunt of pregnancy is the foramen
07:27
ovale and some of the blood will go from
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the right atrium to the left atrium to
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the left ventricle and then into the
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aorta some blood goes from the right
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atrium to the right ventricle and then
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into the pulmonary arteries the third
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shunt of pregnancy is the ductus
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arteriosus so blood will go from the
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pulmonary arteries through this ductus
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arteriosus into the aorta the blood then
08:04
goes from the aorta down to the common
08:08
le X and then from the common iliac
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there are the internal iliac s– which
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then branch to the umbilical arteries
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back to the placenta so remember that it
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is oxygenated blood that flows from the
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umbilical vein I’m going to represent
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this in red it goes from the umbilical
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vein through the first shunt of the
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ductus venosus up through the second
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shunt of the foramen ovale and then
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through the third shunt of the ductus
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arteriosus I’m gonna represent the blood
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flow now in purple to represent that
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it’s mixing with the oxygenated blood
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and at the end of the circuit I’ll
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change to blue to represent the fully
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deoxygenated blood what happens in the
08:51
placenta
08:52
here’s the umbilical cord and then here
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is the placenta the placenta is a unique
08:59
organ of pregnancy for it is partially
09:01
fetal and partially maternal we’ll call
09:04
this top part the fetal portion and the
09:06
bottom portion the maternal portion the
09:09
simplest way to think about this system
09:11
is that the placenta has pools of
09:13
maternal blood so here are the pools of
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maternal blood and the fetus inserts its
09:23
capillaries into these pools of maternal
09:27
blood trophoblastic cells help with this
09:32
invasion process it is at these sites of
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intersection of fetal and maternal
09:38
tissues that oxygen and excretion of co2
09:41
cross the placenta by simple diffusion
09:43
glucose and amino acids are other
09:45
solutes that are transferred from the
09:47
mother to the fetus at these sites thus
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we conclude the video about Peggy
09:52
preggers and the amazing changes that
09:54
occur throughout the three trimesters of
09:55
her pregnancy we have discussed the
09:57
maternal physiologic and anatomic
09:59
changes associated with pregnancy
10:00
The Associated physical exam and
10:02
diagnostic study changes during this
10:04
time as well as fetal and placental
10:06
physiology