Amniocentesis
Author: Craig V. Towers M.D.
Objectives: Upon the completion of this CNE article, the reader will be able to:
1. Describe how the amniocentesis
procedure has changed over the years and the best approach currently for
performing the procedure to minimize complications.
2. Explain
the various risks and complications associated with amniocentesis.
3. Explain the significance of brown
colored fluid that may be obtained at the time of genetic amniocentesis and the
use of amniocentesis in Rh-negative women.
4. Describe how intra-amniotic bleeding
that can occur at the amniocentesis site, may appear
sonographically.
Introduction and History
The first reports regarding the amniocentesis procedure
occurred by Von Schatz, Lambl, and Prochownick in the 1870’s and early
1880’s. These early procedures were used
to relieve patients that were suffering from severe polyhydramnios. In 1930, Menees reported performing the
procedure on pregnant women for the purpose of amniography.
The main focus of the amniocentesis changed to that of a
diagnostic procedure in the mid 1950’s.
These early procedures were for fetal gender determination based in part
on the research of the Canadian anatomist, Murray Barr, who described the “Barr
body” in 1949. When more than one
X-chromosome is present, one is usually active and the other is
inactivated. The inactivated
X-chromosome forms a chromatin mass called a Barr body. The sex chromosome makeup for females is two
X’s and for males is an X and a Y.
Therefore, females will have a barr body and males do not. In 1956, Fuchs and Riis reported performing
amniocentesis procedures to determine fetal sex by analysis of the presence or absence of the Barr body.
In the mid 1960’s, Steele, Bregs, and Nadler described the
performance of amniocentesis procedures in order to culture cells for a full
chromosome analysis and to also measure the level of alpha-fetoprotein (AFP) –
hence the birth of the genetic amniocentesis.
Since the late 1960’s, amniocentesis has become a very common
obstetrical procedure, not only for genetic evaluation, but also for diagnosing
other issues such as infections, fetal maturity, relieving polyhydramnios, and
in analyzing Rh sensitized women.
The Risks of Amniocentesis
From a statistical point of view, amniocentesis is a very
safe procedure with an overall complication rate that is very low (usually less
than 1%). However, the complications
that might occur can be devastating to a family such as injury to the fetus or
loss of the pregnancy. Therefore, the
procedure should never be taken lightly.
The pregnant couple should understand the reason why they might have the
procedure performed and agree to having it done. This is especially true for pregnancies that
have not reached viability (such as the majority of genetic procedures).
The complications related to amniocentesis include pregnancy
risks of rupturing the membranes, causing bleeding, and introducing infection –
all of which might result in the loss of the pregnancy. The fetal risks can include trauma from the
needle and/or death (primarily due to the pregnancy delivering prior to
viability), while the maternal risks reported have included intra-abdominal
infections, sepsis, amniotic fluid embolus, and endometriosis in the needle
track.
The majority of reports on fetal trauma have described scars
or markings on the skin of the limbs and torso; however, there have been case
reports of central nervous system bleeds, ocular damage, and laceration of
intra-abdominal organs. The majority of
these case reports have occurred prior to the use of ultrasound as an aid in
performing the procedure. Yes, believe
it or not, in the late 1960’s and early 1970’s amniocentesis was performed
blindly without the use of ultrasound.
The main concern in performing amniocentesis is a
complication that results in the premature delivery of the pregnancy. In regard to amniocentesis, pregnancy can be
divided into 3 or 4 time periods and each has a different set of circumstances. These categories are the term or near term
pregnancy (> 34 weeks gestation), the previable pregnancy (< 23
weeks gestation) and the potentially viable but premature fetus (which is 23 to
34 weeks gestation and this category might be divided into the significantly
premature 23 weeks up to 30 weeks and the moderately premature 30 to 34 weeks
gestation).
If a patient is term or near term (> 34 weeks
gestation) and the procedure is performed for fetal maturity, or to relieve
polyhydramnios, or to diagnose infection and the membranes rupture, this might
result in the delivery of a baby that needs intensive care therapy for
delivering somewhat early. However, in
most cases the child will survive and develop normally barring any unforeseen
congenital problems. If the procedure is
performed in the previable gestational age and the pregnancy delivers, it is
lost, which can be difficult for some pregnant couples to handle emotionally,
but the tragedy ends. The most difficult
time period to deal with is the viable pregnancy that is significantly
premature (23 weeks up to 30 weeks gestation); because the child can survive
but might have long term sequelae related to prematurity if delivered. The gestational age of 30 to 34 weeks is more
controversial. Neonatal intensive care
therapy has greatly improved over the years and the majority of these neonates
do well. However, their risk is still
higher than a pregnancy that goes beyond 34 weeks gestation. Therefore, all pregnant women who decide to
have an amniocentesis need to have good informed consent but the issues
involved will differ depending on the gestational age.
The majority of studies that have analyzed the pregnancy loss
rate related to the procedure have focused on the genetic amniocentesis
performed prior to viability or less than 23 weeks gestation. When evaluating these studies, multiple
factors come into play including the use of ultrasound and how ultrasound is
utilized, the gauge of the needle, experience of the performer, fluid color,
the number of procedures required in order to obtain enough fluid,
transplacental approach, and maternal history.
Another difficulty that is encountered when looking at the
various studies is how “a pregnancy loss” was defined. There are well over 50 studies in the
literature that have analyzed the loss rate following amniocentesis. Some of these have compared the survival rate
all the way up to 7 days after delivery, whereas others have analyzed the loss
rate up to 28 weeks gestation. Still
others have only compared the loss rate up to 24 weeks or only within 1 to 4
weeks following the procedure. As you
can see, it is difficult to determine the true definition of a loss following
the procedure. In addition, some of
these studies only report their outcome with no comparison or controls. Furthermore, nearly all of them are
retrospective meaning that the data was collected at a later date.
To compare the loss rate differences between pregnancies that
had an amniocentesis versus those that did not seems quite long, when including
the time up to delivery and the first 7 days of life of the newborn. This brings into play the differences in how
pregnancies were handled once viability was reached and may not be a true
indication of the actual risk of the procedure.
If one analyzes only the prospective controlled studies that evaluated
the loss rate up to 28 weeks gestation, the difference between the two groups
(those with amniocentesis versus those without) is about 0.4% to 0.5%, which is
1 in 200 to 1 in 250. This risk of 1 in
200 to 1 in 250 is probably the most often used risk rate quoted for
amniocentesis and was the rate found in the United States Collaborative study.
Many other studies are in print that have listed loss rates
ranging from 1 in 150 to 1 in 500, but again, most of these are retrospective
without controls and vary on the use of ultrasound, experience of the
performer, the needle size, and number of attempts. Currently there is only one prospective
randomized study on genetic amniocentesis and this will probably never be
performed again for ethical reasons. The
study by Tabor, et al, was published in 1986 and involved 4,606 low risk women
ages 25 to 34 who were randomized to have a genetic amniocentesis versus no
amniocentesis and the loss rate difference was 1 in 100 or 1%. The original study reported the use of an
18-gauge needle but this was later described as a 20-gauge needle in a letter
to the editor.
As stated before, several factors need to be examined in
regard to amniocentesis and its complications.
The following list includes the more significant issues:
1. The use of
ultrasound and how it is utilized.
2. The gauge of
the needle.
3. The
experience of the performer.
4. The number of
attempts to be successful.
5. Whether the
needle traverses the placenta.
6. Fluid color.
7. Maternal
history.
When the literature is analyzed, it becomes very clear that
the use of ultrasound and how it is utilized is very important if not the most
important factor in minimizing the risk of the procedure. The other factors in the list are important;
however, without ultrasound, you are in essence blind. The literature actually shows us how the use
of ultrasound with amniocentesis has changed over the years. As previously stated, the first procedures
were performed blindly without the use of ultrasound. This was followed by only using ultrasound to
identify fetal viability and placental location. The next step in progression was to use
ultrasound to mark a site on the abdomen where a pocket of fluid was seen. However, studies showed that these pockets
are often transient due to fetal movement and the fullness of the maternal
bladder. It is clear based on the
literature that the best approach for amniocentesis in order to minimize the
number of attempts that are needed in order to obtain enough fluid and to
minimize the number of “bloody” taps is to perform continuous ultrasound
guidance during the procedure.
A technique that is commonly utilized in continuous
ultrasound guidance is to initially use the ultrasound transducer to identify a
pocket of fluid free of the fetus and umbilical cord and to determine the angle
of the needle insertion and approximate depth.
The transducer can then be placed several centimeters away from the
insertion site at an angle that allows the performer to observe the actual needle
penetration and path into the pocket of fluid (figure 1). This technique seems to decrease the number
of bloody taps and decrease the failure rate.
Currently, before an amniocentesis is attempted, an
ultrasound should be performed to determine fetal viability and position,
placental location, number of fetuses, and gestational age. In addition, the diagnostician should
determine the location of amniotic fluid pockets and look for issues that might
increase the difficulty of the procedure such as uterine fibroids, etc.
In regard to needle size, it appears that the smaller gauge
needles (size 20 or 22) have less problems than larger bore needles such as 18
or 19 gauge needles. In addition, the
experience of the performer will decrease the failure rate and the number of
bloody taps.
A failure to obtain fluid can occur despite the use of
continuous ultrasound guidance with an experienced performer. The more common causes for failure are as
follows:
1. Tenting of
the membranes.
2. Isolated uterine wall contraction
(which distorts the fluid pocket or makes entry into the amniotic sac
unsuccessful).
3. Fetal
movement that changes the shape of the fluid pocket.
4. A changing
maternal bladder size.
Membrane tenting is a frustrating situation where the needle
traverses the uterine musculature, but instead of puncturing the membranes and
entering the fluid pocket, the needle actually pushes the membranes off the
inner uterine wall.
The issue of transplacental procedures is one of
controversy. Several authorities believe
that traversing the placenta can increase the complication rate, while others
disagree. The majority of studies do not
have enough cases of transplacental needle passage to actually make a
comparison. It does seem apparent that
intra-amniotic bleeding is more common following a transplacental procedure,
however, membrane tenting is less common.
Most experienced individuals will try to avoid the placenta if possible.
Finally, a common question is whether an amniocentesis is
more risky in patients who have a history of pregnancy loss. Very few studies are in existence that have
analyzed this question. Most studies
outside of amniocentesis have shown that women with a history of first
trimester pregnancy loss who make it past the first trimester have no higher
complication rate when compared to women who do not have a history of pregnancy
loss. This would suggest that the
primary problem in these women is the first trimester. In that respect, most amniocentesis
procedures occur after the first trimester.
The majority of genetic amniocentesis procedures are
performed between 15 and 20 weeks of gestation.
One of the arguments against this time period is that the result is
obtained later in the pregnancy making it more difficult to act upon. Therefore, an “early amniocentesis” procedure
has been reported, which is one that is performed between 11 and 14 weeks
gestation. Several studies have looked
at the loss rate with early amniocentesis compared to routine amniocentesis and
the majority have shown only a slightly higher rate with the early
procedure. Therefore, it might be
prudent to recommend that women who have a history of first trimester pregnancy
loss wait until they go beyond the first trimester before an amniocentesis is
performed. This issue, however, is a
discussion that should occur between the patient and her healthcare
provider.
The Significance of Brown Fluid
When a genetic amniocentesis is performed, the amniotic fluid
should be clear. Periodically, a brown or green colored fluid is
encountered. From 30,257 genetic
procedures obtained from combining 16 different studies, a total of 677 brown
or green fluid samples were identified for an overall occurrence of about 2%
(range of 1% to 7%). The pregnancy
outcome was reported for 517 of these cases.
A total of 62 pregnancies were lost for a rate of 12%. This is higher than the loss rate for
pregnancies with clear fluid but not unexpected when the cause for the
discoloration is revealed.
When the pigment is analyzed, the result is hemoglobin in
over 90% of the cases. This is
consistent with the fact that in over 50% of cases in which discolored fluid is
found, a history of bleeding during the pregnancy has occurred. Usually, the hemoglobin content is adult
suggesting it is from the mother, but occasionally it can involve fetal
hemoglobin. In addition, if the amniotic
fluid AFP is elevated in the presence of this fluid, the fetal loss rate is
even higher (again suggesting that the discoloration was fetal in origin).
Intra-amniotic Bleeding and Potential Concerns
In most cases, once the needle has entered the amniotic sac
and fluid is obtained, the ultrasonographer will turn their attention to the
fetus and other intrauterine contents.
However, if the site where the needle penetrates the intrauterine cavity
is observed after the needle is removed, intrauterine bleeding can be
seen. One prospective study identified
intrauterine bleeding in 38% of the cases (in which the placenta was not traversed),
but the bleeding stopped in less than 30 seconds over 90% of the time. There were no differences in pregnancy
outcome when the pregnancies with bleeding were compared to no bleeding. This would suggest that visible bleeding is a
normal occurrence with amniocentesis but is also unavoidable. In fact, in a few cases, the bleeding lasted
for several minutes and intrauterine clots developed (figures 2, 3 &
4). If healthcare providers are unaware
that this can occur, they might misinterpret these clots as fetal
malformations, masses, or amniotic bands, etc.
The fact that in utero visible bleeding can occur raises a
concern with performing an amniocentesis on pregnant women who have a blood
borne infection that may not cross the placenta under normal
circumstances. For example, studies have
shown that the majority of newborns infected with the hepatitis B virus become
infected at the time of delivery. This
is why obstetrics tries to identify pregnant women who are carriers of this
virus and immunize the baby at delivery to potentially prevent infection. However, an amniocentesis on a hepatitis B
carrier might expose the neonate to the virus several weeks to months before
the delivery without the benefit of immunization. Unfortunately, at the present time, it is
unknown whether an amniocentesis is potentially harmful in exposing the neonate
to certain maternal blood borne infections such as hepatitis B or HIV (human
immunodeficiency virus) etc.
Amniocentesis and Rh Negative Women
Several studies have been performed that have analyzed
whether an amniocentesis increases the potential for fetal to maternal
hemorrhage. To answer this question,
researchers used the Kleihauer-Betke test (an analysis of maternal blood for
the presence of fetal cells) or a rise in the maternal serum AFP level. In short, nearly every study has shown that
fetal to maternal bleeding does occur with some amniocentesis procedures. For the most part, these fetal to maternal
bleeds are very small and do not result in any untoward outcome. However, in a pregnant woman who is Rh
negative (who might be carrying an Rh positive fetus), exposure to Rh positive
fetal blood could sensitize her to the Rh antigen and lead to significant
future obstetrical difficulties.
Therefore, the Rh status of pregnant women should be known prior to the
procedure and those who are Rh negative should be offered Rhogam to potentially
prevent the risk of sensitization. The
administration of anti-D immunoglobulin (Rhogam) is recommended by ACOG for
pregnant women who are Rh negative.
Summary
Amniocentesis is a common obstetrical procedure that has a
very low complication rate. It is the
use of ultrasound that has primarily reduced this rate. An amniocentesis can be used to obtain very
important information for the pregnant couple and for healthcare
personnel. However, it is important to
understand why the procedure is suggested and the couple should have good
informed consent. In addition, the
information that is to be obtained from the amniocentesis should have the
potential of affecting the course of the pregnancy.
Figures
1 The path of the
amniocentesis needle directed into the amniotic sac.
2 The path of the
amniocentesis needle through the edge of the placenta
3 A stream of bleeding seen
after the needle was removed.
4 A clot of blood collected next to the
fetal head (the baby delivered at term and was entirely normal).
References or Suggested Reading
1. American College of Obstetricians and Gynecologists. Prevention of Rh D alloimmunization. Washington DC
1999 p. 1-8 Practice Bulletin #4.
2. Benacerraf BR, Frigoletto FD:
Amniocentesis under continuous ultrasound guidance: a series of 232 cases. Obstet Gynecol 1983;62:760-763.
3. Bowman JM, Pollock JM: Transplacental
fetal hemorrhage after amniocentesis.
Obstet Gynecol 1985;66:749-754.
4. Chinn DH, Towers CV, Beeman RG, Miller
EI: Sonographically demonstrated intra-amniotic hemorrhage following
transplacental genetic amniocentesis. J
Ultrasound Med 1990;9:495-501.
5. Gold RB, Goyert GL, Schwartz DB, et al:
Conservative management of second-trimester post-amniocentesis fluid
leakage. Obstet Gynecol 1989;74:745-747.
6. Hankins GDV, Rowe J, Quirk JG, et al:
Significance of brown and/or green amniotic fluid at the time of second
trimester genetic amniocentesis. Obstet
Gynecol 1984;64:353-358.
7. Legge M: Dark brown amniotic fluid -
identification of contributing pigments.
Br J Obstet Gynaecol
1981;88:632-34.
8. Mennuti MT, Brummond W, Crombleholme
WR, et al: Fetal-maternal bleeding associated with genetic amniocentesis. Obstet Gynecol 1980;55:48-54.
9. O’Brien WF: Midtrimester genetic
amniocentesis: A review of the fetal risks.
J Reprod Med 1984;29:59-63.
10. NICHD National Registry for Amniocentesis
Study Group. Midtrimester amniocentesis for prenatal diagnosis, safety and accuracy. JAMA
1976;236:1471-6.
11. Platt LD, DeVore GR, Gimovsky ML: Failed
amniocentesis: the role of membrane tenting.
Am J Obstet Gynecol
1982;144:479-480.
12. Romero R, Jeanty P, Reece EA, et al:
Sonographically monitored amniocentesis to decrease intraoperative
complications. Obstet Gynecol 1985;65:426-30.
13. Simpson NE, Dallaire L, Miller JR, et al:
Prenatal diagnosis of genetic disease in Canada: Report of a collaborative
study. Can Med Assoc. J 1976;115:739-746.
14. Stark CM, Smith RS, Lagrandeur RM, et al:
Need for urgent delivery after third- trimester amniocentesis. Obstet Gynecol 2000;95:48-50.
15. Tabor A, Madsen M, Obel Eb, et al:
Randomized controlled trial of genetic amniocentesis in 4606 low-risk
women. Lancet 1986;1:1287-93.
16. Tabor A, Philip J, Bang J, et al: Needle
size and risk of miscarriage after amniocentesis. Letter to the Editor. Lancet
1988;1:183-184.
17. Thomsen SG, Isager-Sally L, Lange AP, et
al: Elevated maternal serum alpha-fetoprotein caused by midtrimester
amniocentesis: A prognostic factor.
Obstet Gynecol 1983;62:297-300.
18. Tongsond T, Wanapirak C, Sirivatanapa, et
al: Amniocentesis-related fetal loss: A cohort study. Obstet Gynecol 1998;92:64-67.
19. Towers CV, Chinn DH, Asrat T, et al:
Intraamniotic bleeding following transabdominal amniocentesis. J Maternal-Fetal Med 1993;2:133-137.
20. Zorn EM, Hanson FW, Greve LC, et al:
Analysis of the significance of discolored amniotic fluid detected at
midtrimester amniocentesis. Am J Obstet
Gynecol 1986;154:1234-1240.
About the Author
Dr. Towers is currently on a sabbatical writing a series of
books that deal with the safety of over-the-counter drugs, herbal medications,
and natural remedies used during pregnancy.
The first is in print entitled “I’m Pregnant & I Have a Cold – Are
Over-the-Counter Drugs Safe to Use?” published by RBC Press, Inc.
Before his sabbatical, Dr. Towers was an Associate Professor
in the Department of Obstetrics and Gynecology at the University of California,
Irvine. He also was the Director of
Perinatal Medicine at Long Beach Memorial Women’s Hospital in Long Beach
California. He has practiced clinically
in the states of Kansas, California, and Wisconsin. Dr. Towers has multiple
publications in peer review medical journals and he has given lectures on a
wide variety of obstetrical topics nationwide.
Examination:
1. The first reports regarding the
amniocentesis procedure that occurred in the 1870’s and early 1880’s were
performed
A. for the determination of fetal sex.
B. for detecting the possibility of
infection.
C. in order to do amniography.
D. for detecting possible problems in Rh
negative women.
E. to relieve patients that were suffering
from severe polyhydramnios.
2. When more than one X-chromosome is
present, one is usually active and the other is inactivated. The inactivated X-chromosome forms a
chromatin mass called a
A. Fuchs body.
B. Riis body.
C. Barr body.
D. Menees body.
E. Lambl body.
3. From a statistical point of view,
amniocentesis is a very safe procedure with an overall complication rate that
is usually less than
A. 5%
B. 1%
C. 10%
D. 2%
E. 7%
4. The complications related to
amniocentesis include all of the following EXCEPT
A. pregnancy
risks of rupturing the membranes and bleeding
B. fetal
risks of trauma and or death
C. maternal risks of intra-abdominal
infection
D. fetal
risks of endometriosis in the needle track
E. maternal
risks of amniotic fluid embolus
5. The main concern in performing
amniocentesis is a complication that results in
A. an amniotic fluid embolus.
B. fetal trauma.
C. the premature delivery of the
pregnancy.
D. the development of endometriosis.
E. fetal infection.
6. Regarding amniocentesis, the most
difficult time period to deal with is
A. the viable pregnancy that is
significantly premature (23 weeks up to 30 weeks gestation).
B. the viable pregnancy at term or near
term (> 34 weeks gestation).
C. the viable pregnancy that is premature
(30 to 34 weeks gestation).
D. the previable pregnancy (from 15 to 22
weeks gestation).
E. the previable pregnancy (from 11 to 14
weeks gestation).
7. The majority of studies that have
analyzed the pregnancy loss rate related to the procedure, have focused on the
A. amniocentesis used for ruling out
infection.
B. term amniocentesis used for determining
fetal lung maturity.
C. amniocentesis used for determining
problems seen in Rh negative women.
D. genetic amniocentesis performed prior to
viability.
E. amniocentesis performed for relieving
pressure seen with polyhydramnios.
8. A pregnancy loss rate following
amniocentesis of 1 in 200 to 1 in 250 is probably the most often used risk rate
quoted and was the rate found in the United States Collaborative study. However, to date there has only been one
prospective randomized study on genetic amniocentesis, which identified a loss
rate of
A. 1
in 100 or 1%
B. 1
in 1000 or 0.1%
C. 1
in 500 or 0.2%
D. 1
in 10 or 10%
E. 1
in 2000 or 0.05%
9. The more significant issues involved in
regard to amniocentesis and its complications
include all of the following EXCEPT
A. the
use of ultrasound and how it is utilized
B. the
gauge of the needle
C. the
number of attempts needed to be successful
D. the
experience of the performer
E. the
amount of fluid obtained
10. Studies have shown that amniotic fluid
pockets are often transient due to
A. the gauge of the needle
B. fetal movement
C. the color of the fluid
D. the transducer that is used
E. the number of attempts needed to be
successful
11. Currently, before an amniocentesis is
attempted, an ultrasound should be performed to determine all of the following
EXCEPT
A. fetal viability
B. the uterine wall thickness
C. fetal position
D. placental location
E. the number of fetuses
12. In regard to needle size, it appears that
fewer problems occur with smaller gauge needles of the _______ size.
A. 12
to 14
B. 14
to 16
C. 16
to 14
D. 18
to 20
E. 20
to 22
13. Common causes for amniocentesis failure
include all of the following EXCEPT
A. tenting
of the membranes
B. isolated
uterine wall contraction which distorts the fluid pocket
C. the
needle bending on the skin upon insertion
D. fetal
movement that changes the shape of the fluid pocket
E. a
changing maternal bladder size
14. Membrane tenting is
A. where the needle traverses the abdominal
wall but diverts when entering the uterine wall.
B. the description of membranes that are
already separated before the amniocentesis is attempted.
C. where a “tent” of blood develops
between the uterine wall and the membrane after the procedure is completed.
D. where an isolated uterine wall contraction
develops as the needle enters the uterine wall, which distorts the amniotic
fluid pocket.
E. where the needle traverses the uterine
wall, but instead of puncturing the membranes, the needle actually pushes the
membranes off the inner uterine wall.
15. A transplacental amniocentesis procedure
is controversial; however
A. most authorities believe that traversing
the placenta almost always increases the complication rate
B. most
authorities believe that traversing the placenta never increases the complication rate
C. there are numerous studies on this
topic, and thus, there should not be any concerns
D. it seems apparent that intra-amniotic
bleeding is more common with a transplacental procedure, however, membrane
tenting occurs less often
E. most
diagnosticians prefer to traverse the placenta if at all possible.
16. An “early amniocentesis” procedure is one
that is performed between _______ weeks gestation.
A. 7 and 9
B. 11 and 14
C. 15 and 20
D. 20 and 23
E. 34 and 37
17. Brown fluid obtained at the time of
genetic amniocentesis
A. is
seen on average about 12% of the time
B. reveals
that the pigment usually consists of intestinal contents
C. occurs
on average about 2% of the time and the pigment is usually hemoglobin
D. is a common occurrence and is not
associated with a higher pregnancy loss rate
E. has
nothing to do with the amniotic fluid AFP level
18. Intra-amniotic bleeding from the
amniocentesis insertion site
A. rarely
occurs if ever
B. when
seen usually lasts for more than 30 seconds
C. could result in inutero clots that
might cause a fetal malformation
D. is
probably a normal occurrence
E. could
result in inutero clots that will lead to the development of fetal masses
19. The fact that in utero visible bleeding
can occur raises a concern with performing an amniocentesis on pregnant women
who have
A. a blood borne infection that may not
cross the placenta under normal circumstances.
B. diabetes.
C. hypertension.
D. lupus.
E. a maternal history of frequent pregnancy
loss.
20. Fetal to maternal bleeding with
amniocentesis
A. when it occurs, is usually very small
and does not result in any untoward outcome
B. can
be of concern for Rh positive pregnant women
C. can
be of concern for the Rh negative fetus
D. has
been studied by using the Kleihauer-Betke test which analyzes fetal
blood for the presence
of maternal cells
E. will
usually decrease the maternal serum AFP level, if it occurs
