Diagnostic ultrasound ( PDFDrive )

CHAPTER 44 Cervical Ultrasound and Preterm Birth 1507
and cerclage is not clearly indicated in this setting. 94 Cerclage
may increase the risk of PTB in women with a twin pregnancy
and an ultrasonographically detected cervical length less
than 25 mm and thus is not recommended. 88,95 In addition,
evidence is lacking for the beneit of cerclage solely for the
following indications: prior LEEP, cone biopsy, or müllerian
anomaly.
Cervical Incompetence and Vaginal Pessary
Cervical pessary is a silicone device that has been used in the
past 50 years to prevent PTB. Two randomized controlled studies
have assessed the efectiveness of this treatment option in women
with singleton gestations and a mid-trimester short cervical length
detected by TVS and with no prior history of PTB, one of which
is in favor (PECEP trial) 62 and the other one from China, which
did not show signiicant beneit to using this device. 96
A Cochrane review in 2010 (before these two trials were
published) 97 did not identify any well-designed randomized
clinical trial in order to conirm or refute the beneit of cervical
pessary in singleton gestations. However, it was noted that there
is evidence from nonrandomized trials that showed some beneit
of cervical pessary in preventing PTB. At this time, evidence
remains controversial.
Vaginal Progesterone and 17-Alpha
Hydroxyprogesterone Caproate
It is important to note that progesterone and 17-alpha hydroxyprogesterone
caproate (17α-OHPC) have diferent chemical
structures, pharmacologic efects, clinical indications, and safety
proiles. 98 Progesterone is a natural progestogen, whereas 17α-
OHPC is a synthetic progestogen. Vaginal progesterone is recommended
for the prevention of PTB in women with a short cervix
(with or without a history of PTB). 17α-OHPC is currently
recommended for the prevention of PTB in women with a
singleton gestation and a history of PTB. Currently, there is a
safety warning for 17α-OHPC based on a nonsigniicant increased
rate of stillbirth and miscarriages in women who received 17α-
OHPC, 99 whereas no such issues have been reported with vaginal
progesterone.
MANAGEMENT PROTOCOLS FOR THE
ABNORMAL CERVIX
Because of improved test characteristics in women at increased
risk of SPTB, and because interventions such as cerclage and
progesterone therapy may have a potential beneit in the high-risk
patient, cervical length measurement is currently used as a
screening test in high-risk pregnancies and perhaps in the future,
universally for all pregnancies. What remains to be determined
is the frequency of evaluation, the gestational age of irst evaluation,
and the utility of the measurements ater 30 weeks of
gestation. Based on the previous discussions, speciic management
protocols are suggested (Figs. 44.17 and 44.18).
CONCLUSION
TVS is the reference-standard approach for cervical assessment
in pregnancy. Cervical length is used most oten to predict SPTB.
Cervical length should be taken in the context of maternal risk
factors for SPTB (obstetric history, uterine contractions), gestational
age, funneling, response to fundal pressure, previous
measurement, presence of cervical glandular area, and amniotic
luid debris. he cervical length cutof of 25 mm at mid-trimester
provides the best predictive values for SPTB before 34 weeks. A
“short” (<25 mm) cervical length is not a diagnosis of impending
SPTB, but rather a tool to quantify the increased risk of such an
event.
Singleton gestations
No prior preterm birth
Prior preterm birth
17α-OHPC
Single TVS measurement at 18-24 weeks
Serial TVS measurement of
cervix length at 16-24 weeks
Cervix length < 25 mm
Cervix length > 25 mm Cervix length < 25 mm Cervix length > 25 mm
Vaginal progesterone
Routine care
Cerclage
Continue 17α-OHPC
Continue 17α-OHPC
FIG. 44.17 Management Protocol: General Obstetric Population. Proposed algorithm to guide response to cervical length measurements
at transvaginal sonography (at 18-24 weeks’ gestation). 17α-OHPC, 17-alpha Hydroxyprogesterone caproate. TVS, transvaginal sonography.