Diagnostic ultrasound ( PDFDrive )

CHAPTER
44
Cervical Ultrasound and Preterm
Birth
Hournaz Ghandehari and Phyllis Glanc
SUMMARY OF KEY POINTS
• There is a signiicant association between cervix length
and the risk of preterm birth.
• A cervical length of more than 3 cm has a high negative
predictive value for delivery at less than 34 weeks’
gestation.
• The most reliable method of documenting cervical length
is transvaginal ultrasound.
• The single most reliable parameter for cervical assessment
is a short cervical length.
• The earlier in gestation, the shorter the cervix, the greater
is the risk of spontaneous preterm birth before 34 weeks,
with the best predictive value when cervical length
measures less than 25 mm.
• Rate of cervical change may be a better predictor than
cervical length.
CHAPTER OUTLINE
PRETERM BIRTH
SONOGRAPHY OF THE UTERINE
CERVIX
Transabdominal Approach
Transperineal/Translabial Approach
Transvaginal Sonography
Technical Limitations and Pitfalls
Normal Cervix
“Short” Cervix
PREDICTION OF SPONTANEOUS
PRETERM BIRTH
Obstetric Factors
Cervical Funneling
Rate of Cervical Change
Dynamic Cervical Change
Other Sonographic Features
CERVICAL ASSESSMENT IN
SPECIFIC CLINICAL SCENARIOS
Asymptomatic Patients
General Obstetric Population
Screening
High-Risk Obstetric Population
Screening
Symptomatic Patients
Cervical Incompetence and Cervical
Cerclage
Cervical Incompetence and Vaginal
Pessary
Vaginal Progesterone and 17-Alpha
Hydroxyprogesterone Caproate
MANAGEMENT PROTOCOLS FOR
THE ABNORMAL CERVIX
CONCLUSION
Acknowledgment
PRETERM BIRTH
Preterm birth (PTB), deined as delivery before 37 weeks of
gestation, occurs in 5% to 11% of all pregnancies, ranging from
as low as 5% in some European countries to 15% in the United
States and to as high as 18% in some African countries, attributable
to geographic, socioeconomic, and racial disparities. 1-3 PTB is
the leading cause of neonatal morbidity and mortality not
attributable to congenital anomalies or aneuploidy. If an infant
is born preterm, the risk of death in the irst year of life is 40-fold
greater compared with an infant born at term. 2
Immediate consequences of PTB include respiratory distress,
intraventricular hemorrhage, sepsis, and retinopathy of prematurity.
2 In the long term, infants born preterm represent one-half
the children with cerebral palsy, one-third of those with abnormal
vision, one-quarter of those with chronic lung disease, and
one-ith of children with mental retardation. 2,4,5 he morbidity
of prematurity persists to adulthood, with an increased incidence
of behavioral problems, lower levels of educational achievement,
reduced rates of reproductive success (with incidence of both
conception and live birth adversely afected), and an increased
incidence of second-generation PTB. 6-8
he risk of prematurity persists in subsequent pregnancies,
with a twofold increased risk in the next pregnancy and up to
50% risk of PTB if the woman has experienced two or more
prior PTBs. 2 Given the substantial and far-reaching impact of
PTB, it is important to recognize patients at increased risk of
spontaneous preterm birth (SPTB), such that therapeutic
interventions can be implemented to improve neonatal outcome.
About 85% of preterm deliveries occur spontaneously and
are traditionally classiied as one of three discrete events: preterm
labor (uterine activity with coordinated cervical efacement and
dilation), preterm premature ruptured membranes (ruptured
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