Keywords
Amnioreduction - amnioscope - amniotomy - polyhydramnios
Polyhydramnios is a condition of excessive amniotic fluid, defined as the amniotic
fluid index (AFI) of greater than 25 cm or the single deepest pocket of larger than
8 cm, and is identified in ~1% of all pregnancies.[1] This condition is divided into the idiopathic and pathological conditions. Pathological
polyhydramnios is associated with fetal congenital malformations of the gastrointestinal
tract or central nervous system, fetal hyperdynamic state (fetal anemia, fetal or
placental hypervascular tumors, twin-to-twin transfusion syndrome, etc.), or maternal
diabetes.[2] Serious maternal complications associated with polyhydramnios are placental abruption,
uterine dysfunction, and postpartum hemorrhage.[3] Following a rupture of membranes and an acute outflow of copious amniotic fluid,
the placenta may separate from the uterine wall due to a rapid decompression of the
uterine cavity before delivery of the fetus.[1] Moreover, overstretched uterine muscles may cause weak labor and uterine atony,
which lead to a fourfold increase in cesarean deliveries due to dystocia and a sixfold
increase in postpartum hemorrhage, respectively.[4] When considering an insufficient uterine contraction and poor labor progress, active
artificial amniotomy for more effective labor appears to be the preferred obstetric
approach in women with polyhydramnios. However, the potential risk for serious complications
such as placental abruption and cord prolapse makes obstetricians hesitate to perform
artificial amniotomy. In such a challenging situation, we recently performed pinhole
artificial amniotomy using an amnioscope in our institute. This procedure may be more
convenient and lower risk than conventional artificial amniotomy. Historically speaking,
amnioscopy had played a role in obstetric examinations to screen for meconium-stained
amniotic fluid or to evaluate fetal conditions via fetal scalp blood sampling.[5]
[6] Nowadays, the diagnostic utility of the amnioscope in various clinical conditions
has been rejected time and again, losing its significance as an obstetric instrument.
To our knowledge, there have been no reports describing artificial amniotomy using
amnioscopes to reduce worrisome complications in polyhydramnios. In this article,
we present the results of our pilot clinical study and reevaluate the amnioscope for
a return to obstetric practice.
Materials and Methods
Previously, we performed artificial amniotomy in women with polyhydramnios using a
vaginal speculum. However, in the prolonged latent phase of labor frequently seen
in polyhydramnios, we cannot clearly identify the forebag of the amniotic sac through
a vaginal speculum because of disturbances of the thick circumferential lip of the
cervix and vaginal wall in most cases ([Fig. 1]). Therefore, we came up with the idea that pinhole artificial amniotomy using an
amnioscope with a 26-gauge needle makes it possible for us to perform amniotomy more
easily and safely ([Fig. 2]). From January to March in 2011, we performed pinhole artificial amniotomy using
an amnioscope in four women with polyhydramnios at Osaka University Hospital. We received
written informed consent from each patient before the procedure. The amnioscopes used
in this study have been left unused in the obstetric ward for such a long time that
the manufacturer of the amnioscope is completely unknown. In this study, the causes
of polyhydramnios were all associated with fetal pathological conditions as follows:
tetrasomy 12p, diaphragmatic hernia, large cleft lip and cleft palate, and jejunal
atresia.
Figure 1 Vaginal speculum examination at 3-cm cervical dilatation. Visual field of birth canal
was quite poor due to inadequate dilatation of the uterine cervix and bilateral vaginal
wall compression. The forebag of the amniotic sac was completely invisible.
Figure 2 Instruments used for pinhole artificial amniotomy. Amnioscope tube is inserted into
the vagina with a square plug inside to not injure the vaginal wall during the procedure.
A 26-gauge needle is used for pinhole amniotomy.
Next, we concretely explained the procedure. We laid the patient on a delivery bed
in a lithotomy position. Before and during the procedure, we continuously confirmed
a reassuring fetal status by fetal heart rate monitoring and a fetal vertex position
without a funic presentation by transabdominal ultrasonography. After an adequate
sterilization of patient's vulva and vaginal wall, we manually lifted the anterior
lip of the cervix up with the index and middle fingers during a pelvic examination,
inserted an amnioscope into the vagina through the space between the fingers, and
attached the tip of an amnioscope to the forebag of the amniotic sac. This allowed
the forebag of the amniotic sac to become visible through the amnioscope without any
disturbances ([Fig. 3]). We carefully performed pinhole artificial amniotomy using a 26-gauge needle with
an extended 1-mL syringe ([Fig. 4]), and amniotic fluid started trickling through the pinhole in the amniotic membranes
([Fig. 5]). During pinhole amniotomy, we punctured the forebag of the amniotic sac once or
few times depending on the flow speed of amniotic fluid, which was ideally a couple
of dozen milliliters per minute. After a few hours of the procedure, we performed
complete amniotomy following confirmation of adequate amnioreduction and the engagement
of the fetal head into the pelvis.
Figure 3 A view of the forebag of the amniotic sac through an amnioscope. We inserted an amnioscope
into the vagina through the space between the fingers and attached the tip of the
amnioscope to the forebag of the amniotic sac. The forebag of the amniotic sac was
visible through an amnioscope tube.
Figure 4 Actual operation of pinhole artificial amniotomy using an amnioscope. We carefully
performed artificial amniotomy using a 26-gauge needle with an extended 1-mL syringe
and made from one to several pinholes in the amniotic membranes.
Figure 5 A view after pinhole artificial amniotomy through an amnioscope. Amniotic fluid started
trickling through pinholes in the amniotic membranes, pooling in the amnioscope tube.
In this preliminary study, we performed artificial amniotomy using this method in
four women with polyhydramnios and analyzed the obstetric outcome.
Results
Detailed clinical information of these four deliveries is presented in [Table 1]. In all cases, pinhole artificial amniotomy using an amnioscope was successfully
performed without any problems. There were no deliveries complicated by prolonged
labor or postpartum hemorrhage. The results of blood gas of umbilical artery testing
showed good neonatal condition at birth. To make the process of this procedure clearer,
we present the detailed clinical course of case 1 in [Table 1] as follows.
Table 1
Clinical Data of Four Deliveries Using an Amnioscope for Pinhole Artificial Amniotomy
|
Case No.
|
Age (y)
|
Parity
|
Fetal Cause of Polyhydramnios
|
AFI (cm)
|
Delivery Mode
|
GA (wk)
|
Delivery Time (h)
|
Blood Loss (mL)
|
Neonatal Weight (g)
|
Blood Gas of Umbilical Artery (pH and BE)
|
|
1
|
35
|
0
|
Tetrasomy 12p
|
50
|
VD
|
37
|
11.1
|
210
|
2800
|
pH: 7.300; BE: −6.0
|
|
2
|
39
|
1
|
Diaphragmatic hernia
|
31
|
VD
|
37
|
7.3
|
200
|
2852
|
pH: 7.412; BE: −2.7
|
|
3
|
34
|
0
|
Left cleft lip and cleft palate
|
28
|
VE
|
38
|
11.6
|
600
|
2926
|
pH: 7.319; BE: −5.4
|
|
4
|
25
|
1
|
Jejunal atresia
|
27
|
VD
|
37
|
7.7
|
250
|
3320
|
pH: 7.363; BE: −3.1
|
AFI, amniotic fluid index; BE, base excess; GA, gestational age; VD, vaginal delivery;
VE, vacuum extraction.
In case 1, we induced labor to terminate the pregnancy at 37 weeks' gestation to relieve
maternal discomfort due to polyhydramnios. After mechanical cervical ripening using
a transcervical balloon catheter, intravenous oxytocin administration was started.
At the beginning of induction of labor, the cervix was dilated 3 cm, the AFI was 50
cm, and the fetal head was floating on the cervix. During the first 4 hours of labor,
cardiotocography revealed uterine dysfunction due to polyhydramnios. Therefore, we
performed pinhole artificial amniotomy using an amnioscope, and slow amnioreduction
was started. We punctured the forebag of the amniotic sac twice. Three hours later,
we performed complete amniotomy following confirmation of adequate amnioreduction
(AFI 19 cm) and the engagement of the fetal head into the pelvis at 5-cm cervical
dilatation. Subsequently, the expulsive force was gradually improved, labor proceeded
to active phase, and the patient delivered a 2800-g infant vaginally in 7 hours after
the initial pinhole artificial amniotomy. Total delivery time was 11.1 hours, and
total blood loss at delivery was only 210 mL.
We performed pinhole artificial amniotomy using the amnioscope in the same fashion
for the three other women with polyhydramnios. As a result, we had no complications
related to the use of this procedure, and all women had vaginal delivery without postpartum
hemorrhage and neonatal asphyxia.
Discussion
Amniotomy has many benefits even in the normal course of labor. The presumed advantages
are the acceleration of spontaneous labor, the shortening of labor without adverse
perinatal outcome, the opportunity to apply a scalp electrode and an intrauterine
pressure catheter for monitoring, and early detection of meconium-stained amniotic
fluid.[7] During amniotomy, it is important to take special care not to float the fetal head
from the pelvis to avoid umbilical cord prolapse.[8] Fundal pressure to fix the fetal head into the pelvis may reduce the risk of cord
prolapse.[7] In polyhydramnios, the incidence of cord prolapse following amniotomy is higher
because the overdistended uterus makes it difficult to palpate and fix the fetus during
the procedure, and the rapid outflow of excessive amniotic fluid additionally promotes
cord prolapse. Furthermore, acute uterine decompression following amniotomy may induce
placental abruption. Some obstetricians recommend that slow removal of amniotic fluid
by transabdominal amniocentesis helps to avoid those dangerous complications,[1] but it is clinically difficult to perform amniocentesis during active labor with
frequent uterine contractions. Other obstetricians advocate several membrane punctures
by thin needle with direct visualization of membranes using a vaginal speculum,[7] but it is technically hard to puncture membranes if there is inadequate dilatation
of the uterine cervix at a latent phase of labor or poor visualization of the birth
canal by bilateral vaginal wall compression, especially in the case of maternal obesity.
In contrast, pinhole artificial amniotomy using an amnioscope makes it possible to
reduce the amniotic fluid volume at a slow space during active labor, and it is easy
to visualize the forebag of the amniotic sac without obstruction, even in case of
a latent phase of labor or maternal obesity. In short, this procedure is an optimal
and convenient method for artificial amniotomy in the case of polyhydramnios.
Approximately 40 years ago, the amnioscope was in the limelight as an obstetric device
to detect meconium-stained amniotic fluid.[9] At that time, obstetricians realized that the presence of meconium-stained amniotic
fluid is an anxiety-causing sign for predicting fetal distress or asphyxia. The relationship
between meconium-stained amniotic fluid and fetal asphyxia was a much-debated subject
to reduce perinatal mortality and morbidity, especially in postdate pregnancy.[10]
[11]
[12] Amnioscopes have actively been investigated in clinical research, but studies have
been inconclusive. Recent studies show the mechanism of fetal passage of meconium
is mainly divided into three categories: physiologically normal gastrointestinal tract
maturation, increased bowel peristalsis caused by vagal reflex from common umbilical
cord compression, and a pathological condition reflecting fetal compromise.[13] The overall incidence of meconium-stained amniotic fluid is 12%, and the rates of
meconium-stained amniotic fluid increase from 1.2% at 32 weeks to almost 100% at 42
weeks.[14] Nowadays, it is well known that only a few cases of meconium-stained amniotic fluid
are linked to fetal compromise.[13] On the other hand, another discussion about thick meconium-stained amniotic fluid
has recently been debated.[15] Thus, an amnioinfusion to dilute thick meconium has been advocated as a procedure
to reduce the incidence of meconium aspiration syndrome and improve neonatal outcomes.
However, the American College of Obstetricians and Gynecologists concluded that routine
prophylactic amnioinfusion is not recommended because Fraser's large randomized controlled
study has not found benefits in neonatal outcome and several maternal deaths have
been associated with amnioinfusion.[16]
[17] From these considerations, the detection of meconium-stained amniotic fluid currently
has little impact on obstetric management. Consequently, amnioscopy to screen for
meconium-stained amniotic fluid has never had a place in routine clinical practice.
In the management of pregnancy complicated by idiopathic thrombocytopenia, fetal scalp
blood sampling using amnioscopy to determine the fetal platelet count during labor
has been reported.[18] At that time, if fetal thrombocytopenia was verified, cesarean delivery was anecdotally
preferred for preventing fetal intracranial hemorrhage. However, this procedure is
not only technically difficult but also significantly inaccurate with frequent underestimation
of the fetal platelet count due to in vitro coagulation during the procedure.[19] Furthermore, it is hard to imagine that cesarean delivery is beneficial for the
fetus because labor is already in an active phase at the time of the procedure. So,
current accepted management is to select the mode of delivery only by obstetric indications
without any procedure for determining fetal platelet count in utero.[20] The value of this procedure renders its use moot.
Once, fetal scalp blood pH sampling played a valuable role in the interpretation of
electronic fetal heart rate monitoring for assessment of fetal well-being during labor.[6] Then, the complementary usage of this procedure with cardiotocography was expected
to reduce the rate of cesarean delivery in the setting of nonreassuring fetal heart
rate pattern.[7] However, the cervix needs to be dilated at least 4 to 5 cm and vertex at a −1 station
or below for success.[8] Furthermore, this procedure is cumbersome, is fraught with technical error, and
needs repeated testing during labor. Goodwin et al indicated that fetal scalp blood
pH sampling has been virtually eliminated without an increase both of cesarean delivery
rate due to fetal distress and of perinatal asphyxia.[21] This procedure is now rarely used in standard obstetric care.
In conclusion, the significance of amnioscopy to detect meconium-stained amniotic
fluid or to assist fetal scalp blood sampling has been practically nil in modern obstetric
management. In this article, we describe a new use for the amnioscope as a promising
device for low-risk amniotomy in women with polyhydramnios. Of course, further clinical
investigation is needed to prove the utility of the amnioscope for this purpose and
to search for more effective and safer management of polyhydramnios.
