Occipito posterior position
Diagnosis of malpresentations
Symptoms and Signs Figure
BROW PRESENTATION is caused by partial extension of the fetal
head so that the occiput is higher than the sinciput (Fig
S-16).
On abdominal examination, more than half the fetal head is above
the symphysis pubis and the occiput is palpable at a higher level
than the sinciput.
On vaginal examination, the anterior fontanelle and the orbits
are felt.
For managementFIGURE S-16
FACE PRESENTATION is caused by hyper-extension of the fetal head
so that neither the occiput nor the sinciput are palpable on
vaginal examination (Fig S-17 and Fig S-18).
On abdominal examination, a groove may be felt between the
occiput and the back.
On vaginal examination, the face is palpated, the examiners
finger enters the mouth easily and the bony jaws are felt.
For managementFIGURE S-17
FIGURE S-18
COMPOUND PRESENTATION occurs when an arm prolapses alongside the
presenting part. Both the prolapsed arm and the fetal head present
in the pelvis simultaneously(Fig S-19). For management FIGURE
S-19
BREECH PRESENTATION occurs when the buttocks and/or the feet are
the presenting parts. On abdominal examination, the head is felt in
the upper abdomen and the breech in the pelvic brim. Auscultation
locates the fetal heart higher than expected with a vertex
presentation. On vaginal examination during labour, the buttocks
and/or feet are felt; thick, dark meconium is normal.For
management
COMPLETE (FLEXED) BREECH PRESENTATION occurs when both legs are
flexed at the hips and knees (Fig S-20).FRANK (EXTENDED) BREECH
PRESENTATIONoccurs when both legs are flexed at the hips and
extended at the knees (Fig S-21).
FOOTLING BREECH PRESENTATION occurs when a leg is extended at
the hip and the knee (Fig S-22). FIGURE S-20
FIGURE S-21
FIGURE S-22
TRANSVERSE LIE AND SHOULDER PRESENTATION occur when the long
axis of the fetus is transverse (Fig S-23). The shoulder is
typically the presenting part. On abdominal examination, neither
the head nor the buttocks can be felt at the symphysis pubis and
the head is usually felt in the flank. On vaginal examination, a
shoulder may be felt, but not always. An arm may prolapse and the
elbow, arm or hand may be felt in the vagina.
For managementFIGURE S-23
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Introduction
Postterm pregnancy is defined as a pregnancy that extends to 42
0/7 weeks and beyond.1 The reported frequency of postterm pregnancy
is approximately 3-12%.1,2 However, the actual biologic variation
is likely less since the most frequent cause of a postterm
pregnancy diagnosis is inaccurate dating.3,4,5,6 Risk factors for
actual postterm pregnancy include primiparity, prior postterm
pregnancy, male gender of the fetus, and genetic
factors.7,8,9,2,1
Laursen et al studied monozygotic and dizygotic twins and their
subsequent development of prolonged pregnancies. They found that
maternal but not paternal genetic factors influenced the rate of
postterm pregnancies and accounted for the etiology in as many as
30% of these pregnancies.10 A more recently described risk factor
is obesity, which appears to increase the risk of pregnancies
progressing beyond 41 or 42 weeks of gestation.11,12,13 Although
the last menstrual period (LMP) has been traditionally used to
calculate the estimated due date (EDD), many inaccuracies exist
using this method in women who have irregular cycles, have been on
recent hormonal birth control, or who have first trimester
bleeding. In particular, women are more likely to be
oligo-ovulatory than polyovulatory, so cycles longer than 28 days
are not uncommonly seen.4 If such a cycle is 35 days instead of 28
days, a second trimester ultrasound will not be powerful enough to
redate the pregnancy. Thus, not only the LMP date, but the
regularity and length of cycles must be taken into account when
estimating gestational age.
Ultrasonographic dating early in pregnancy can improve the
reliability of the EDD; however, it is necessary to understand the
margin of error reported at various times during each trimester. A
calculated gestational age by composite biometry from a sonogram
must be considered an estimate and must take into account the range
of possibilities.
Estimation range varies. For example, crown-rump length (CRL) is
3-5 days, ultrasonography performed at 12-20 weeks of gestation is
7-10 days, at 20-30 weeks is 2 weeks, and after 30 weeks is 3
weeks. Thus, a pregnancy that is 35 weeks by a 31-week ultrasound
could actually be anywhere from 32 weeks to 38 weeks (35 wk +/-3
wk). If the calculated ultrasonographic gestational age varies from
the LMP more than the respective range of error, it is used instead
to establish the final EDD. The importance of determining by what
method a pregnancy is dated cannot be overemphasized because this
may have significant consequences if the physician delivers a
so-called term pregnancy that is not or observes a so-called term
pregnancy that is very postterm.
When determining a management plan for an impending postterm
pregnancy (>40 wk of gestation but 4,500 g)35 , they are, in
turn, at greater risk for other complications.36,37 Such
complications associated with fetal macrosomia include prolonged
labor, cephalopelvic disproportion, and shoulder dystocia with
resultant risks of orthopedic or neurologic injury.
Approximately 20% of postterm fetuses have fetal dysmaturity
(postmaturity) syndrome, which describes infants with
characteristics of chronic intrauterine growth restriction from
uteroplacental insufficiency.38 These pregnancies are at increased
risk of umbilical cord compression from oligohydramnios,
nonreassuring fetal antepartum or intrapartum assessment,
intrauterine passage of meconium, and short-term neonatal
complications (such as hypoglycemia, seizures, and respiratory
insufficiency).
Meconium aspiration syndrome refers to respiratory compromise
with tachypnea, cyanosis, and reduced pulmonary compliance in
newborns exposed to meconium in utero and is seen in higher rates
in postterm neonates.39 Indeed, the 4-fold decrease in the
incidence of the meconium aspiration syndrome in the United States
from 1990-1998 has been attributed primarily to a reduction in the
postterm delivery rate21 with very little contribution from
conventional interventions designed to protect the lungs from the
chemical pneumonitis caused by chronic meconium exposure, such as
amnioinfusion40,41 or routine nasopharyngeal suctioning of
meconium-stained neonates.42
Postterm pregnancy is also an independent risk factor for
neonatal encephalopathy43 and for death in the first year of
life.16,17 While much of the work above has been conducted in
postterm pregnancies. Some of the fetal risks such as presence of
meconium, increased risk of neonatal academia, and even stillbirth
have been described as being greater at 41 weeks ofgestation and
even at 40 weeks of gestation as compared with 39 weeks
gestation.22,23 For example, in one study, the rates of meconium
and neonatal academia both increased throughout term pregnancies
beyond 38 weeks of gestation.In addition to stillbirth being
increased prior to 42 weeks of gestation, one study found that the
risk of neonatal mortality also increases beyond 41 weeks of
gestation.44 Thus, 42 weeks does not represent a threshold below
which risk is uniformly distributed. Indeed, neonatal morbidity
(including meconium aspiration syndrome, birth injury, and neonatal
acidemia) appears to be the lowestat around 38 weeks and increase
in a continuous fashion thereafter.45 Maternal risks and mode of
deliveryThe maternal risks of postterm pregnancy are often
underappreciated. These include an increase in labor dystocia
(9-12% vs 2-7% at term), an increase in severe perineal injury (3rd
and 4th degree perineal lacerations) related to macrosomia (3.3% vs
2.6% at term) and operative vaginal delivery, and a doubling in the
rate of cesarean delivery (14% vs 7% at term).18,27,28,29 The
latter is associated with higher risks of complications such as
endometritis, hemorrhage, and thromboembolic disease.28,46
In addition to the medical risks, the emotional impact (anxiety
and frustration) of carrying a pregnancy 1-2 weeks beyond the
estimated due date should not be underestimated. In a randomized,
controlled trial of women at 41 weeks of gestation, women who were
induced would desire the same management 74% of the time, whereas
women with serial antenatal monitoring only desired the same
management 38% of the time.47
Similar to neonatal outcomes, maternal morbidity also increases
in term pregnancies prior to 42 weeks of gestation. Such
complications as chorioamnionitis, severe perineal lacerations,
cesarean delivery rates, postpartum hemorrhage, and endomyometritis
all increase progressively after 39 weeks
ofgestation.23,30,31,32,21 Timing of Delivery
The first decision that must be made when managing an impending
postterm pregnancy is whether to deliver. In certain cases (eg,
nonreassuring surveillance, oligohydramnios, growth restriction,
certain maternal diseases), the decision is straightforward. In
these high-risk situations, the time at which the risks of
remaining pregnant begin to outweigh the risks of delivery may come
at an earlier gestational age (eg, 39 weeks of gestation). However,
frequently several options can be considered when determining a
course of action in the low-risk pregnancy. The certainty of
gestational age, cervical examination findings, estimated fetal
weight, patient preference, and past obstetric history must all be
considered when mapping a course of action.
The main argument against a policy of routine induction of labor
at 41 0/7 to 41 6/7 weeks has been that induction increases the
rate of cesarean delivery without decreasing maternal and/or
neonatal morbidity. Some of the studies that failed to show a
reduction in fetal/neonatal morbidity were diluted by poorly dated
pregnancies that were not necessarily postterm. In addition, the
potential for increasing the risk for cesarean delivery with a
failed induction is far less likely in the era of safe and
effective cervical ripening agents.
To date, more than 10 studies have been published of elective
induction of labor, many of them at 41 weeks of
gestation.48,34,49,50,51,52 The preponderance of the evidence from
these studies, including meta-analyses, find that not only israte
of cesarean delivery not increased in women who were randomized to
routine induction of labor, but alsomore cesarean deliveries were
performed in the noninduction groups, and the most frequent
indication was fetal distress. Even with multiple studies, very few
neonatal differences have been demonstrated. However, the reduction
in meconium is statistically significant andtherate of neonatal
mortality is lower.
In summary, routine induction at 41 weeks ofgestation does not
increase the cesarean delivery rate and may decrease it without
negatively affecting perinatal morbidity or mortality. In fact,both
the woman and theneonate benefitfrom a policy of routine induction
of labor in well-dated, low-risk pregnancies at 41 weeks'
gestation. A policy of routine induction at 40 weeks' has few
benefits, and there are multiple reasons not to allow a pregnancy
to progress beyond 42 weeks.
Prior to 41 weeks of gestation, the evidence becomes more scant
with only 3 small, non-US, randomized, controlled trials comparing
elective induction of labor to expectant management of pregnancy.51
However, elective induction of labor is increasingly being used as
a management strategy.53,54 While this management may be reasonable
in a practice that allows 48 hours or more for the management of
the latent phase and the first stage of labor overall, in a setting
where induction of labor is called a failure after 18-24 hours, it
will likely further increase the cesarean delivery rate.
Prevention of Postterm Pregnancy
As noted above, the most decisive way to prevent postterm
pregnancy is induction of labor prior to 42 weeks gestation.
However, since complications rise during 40 and 41 weeks' gestation
and both clinicians and patients are concerned about the risks of
induction of labor, it is perceivably better for women to go into
spontaneous labor at 39 weeks of gestation on their own. Several
minimally invasive interventions have been recommended to encourage
the onset of labor at term and prevent postterm pregnancy,
including membrane stripping, unprotected coitus, and
acupuncture.
Stripping or sweeping of the fetal membranes refers to digital
separation of the membranes from the wall of the cervix and lower
uterine segment. This technique, which likely acts by releasing
endogenous prostaglandins from the cervix, requires the cervix to
be sufficiently dilated to admit the practitioners finger. Although
stripping of the membranes may be able to reduce the interval to
spontaneous onset of labor, a reduction in operative vaginal
delivery, cesarean delivery rates, or maternal or neonatal
morbidity has not been consistently proven.55,56,57
Unprotected sexual intercourse causes uterine contractions
through the action of prostaglandins in semen and potentially
release of endogenous prostaglandins similar to stripping of the
membranes. Indeed, prostaglandins were originally isolated from
extract of prostate and seminal vesicle glands, hence their name.
Despite some conflicting data, it appears that unprotected coitus
may lead to the earlier onset of labor, reduction in postterm
pregnancy rates, and less induction of labor.58,59,60
In a small randomized trial that attempted to address this
question, women were randomized to a group advised to have coitus
versus a control group that was not. In this study, the women
advised to have coitus did so more often (60% vs 40%), the
difference in the rate of spontaneous labor was not measurablein
this underpowered study.61 Similarly, the efficacy of acupuncture
for induction of labor cannot be definitively assessed because of
the paucity of trial data; this requires further examination.62,63
Cervical Ripening and Intrapartum Management
Once the decision to deliver a patient has been made, the
management of the labor induction depends on the clinical setting,
and a brief review of cervical ripening agents and potential
complications of induction of labor is appropriate. A comprehensive
review of all available methods for cervical ripening, indications,
contraindications, and dosing is beyond the scope of this
article.
As many as 80% of patients who reach 42 weeks' gestation have an
unfavorable cervical examination (ie, Bishop Score 160 beats per
minute
2. Dinoprostone Hyperstimulation Incidence: 17%
3. Misoprostol Hyperstimulation Incidence
1. Intravaginal gel or tablet: 8%
2. Oral crushed form or tablet: 1 to 2%
3. Uterine Rupture in VBAC
1. Risk: 2.5% in Trial of Labor after Cesarean
4. References
1. Crane (2001) Obstet Gynecol 97:926
2. Ravasia (2000) Obstet Gynecol 183:1176
7. Complications: Hyperstimulation Management
1. Consider Terbutaline SQ
2. Dinoprostone (Cervidil): Remove
3. Misoprostol (Cytotec): Irrigate vagina
1. Use Normal Saline via 100 cc Syringe (no needle)
2. Repeat several times until pill fragments recovered
8. References
1. Adair (2000) Clin Obstet Gynecol 43:447
2. Crane (2001) Obstet Gynecol 97:926
3. Sanchez-Ramos (1997) Obstet Gynecol 89:633
4. Tenore (2003) Am Fam Physician 67(10):2123
Dinoprostone (C0012472)
Definition (MSH)The most common and most biologically active of
the mammalian prostaglandins. It exhibits most biological
activities characteristic of prostaglandins and has been used
extensively as an oxytocic agent. The compound also displays a
protective effect on the intestinal mucosa.
Definition (NCI)A synthetic prostaglandin E2 (PGE2) analogue
with smooth muscle contraction inducing property. It has been
suggested that PGE2 regulates the intracellular levels of cyclic 3,
5-adenosine monophosphate (cAMP) by activating adenylate cyclase
and thereby increases cellular membrane calcium ion transport. By
acting directly on the myometrium, dinoprostone induces uterine and
gastrointestinal smooth muscle contractions.
1. Indications
1. Bishop Score 10 contractions in 20 minutes
2. Dinoprostone Tachysystole Incidence: 33%
3. Misoprostol Tachysystole Incidence
1. Intravaginal gel or tablet: 31 to 49%
2. Oral crushed form or tablet: 16 to 22%
2. Hyperstimulation
1. Criteria
1. Exaggerated uterine response (i.e. Tachysystole)
2. Concerning Fetal Heart Rate tracing
1. Late Decelerations
2. Fetal Tachycardia >160 beats per minute
2. Dinoprostone Hyperstimulation Incidence: 17%
3. Misoprostol Hyperstimulation Incidence
1. Intravaginal gel or tablet: 8%
2. Oral crushed form or tablet: 1 to 2%
3. Uterine Rupture in VBAC
1. Risk: 2.5% in Trial of Labor after Cesarean
4. References
1. Crane (2001) Obstet Gynecol 97:926
2. Ravasia (2000) Obstet Gynecol 183:1176
7. Complications: Hyperstimulation Management
1. Consider Terbutaline SQ
2. Dinoprostone (Cervidil): Remove
3. Misoprostol (Cytotec): Irrigate vagina
1. Use Normal Saline via 100 cc Syringe (no needle)
2. Repeat several times until pill fragments recovered
8. References
1. Adair (2000) Clin Obstet Gynecol 43:447
2. Crane (2001) Obstet Gynecol 97:926
3. Sanchez-Ramos (1997) Obstet Gynecol 89:633
4. Tenore (2003) Am Fam Physician 67(10):2123
Dinoprostone (C0012472)
Definition (MSH)The most common and most biologically active of
the mammalian prostaglandins. It exhibits most biological
activities characteristic of prostaglandins and has been used
extensively as an oxytocic agent. The compound also displays a
protective effect on the intestinal mucosa.
Definition (NCI)A synthetic prostaglandin E2 (PGE2) analogue
with smooth muscle contraction inducing property. It has been
suggested that PGE2 regulates the intracellular levels of cyclic 3,
5-adenosine monophosphate (cAMP) by activating adenylate cyclase
and thereby increases cellular membrane calcium ion transport. By
acting directly on the myometrium, dinoprostone induces uterine and
gastrointestinal smooth muscle contractions.