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| UCA acute and obtuse Courtesy Researchgate |
Increasingly wide utero cervical angle
(UCA) after mid trimester cerclage operation signifies increase risk of preterm
delivery.
Dr. Jordan Knight and his colleagues
from Indiana University School of Medicine, Indianapolis, IN presented a pilot
study, utilizing UCA in predicting the failure of mid-trimester transvaginal
cerclage operations. [1]
UCA is defined as the triangular area
between the lower uterine segment and cervical canal measured by Transvaginal Ultrasonography
(TVUS).
Researchers are exploring the
possibilities of using a novel ultrasound parameter, the anterior utero
cervical angle (UCA) as a predictor of Spontaneous Preterm Birth along with
Cervical length (CL). Previously this angle has been used as one of the
parameter for successful induction of labor.
The pathophysiological principle behind this is based on physics
and trigonometry. Pregnant uterus exerts pressure on cervix and depending on the
angle of inclination, the cervix is either shut if the angle is acute or opened
wide if the angle is obtuse.
The current retrospective study
collected data on 142 women who underwent transvaginal cerclage between
2010-2015. UCL was measured thrice in same patient: prior, one week after
cerclage placement and prior to delivery by TVUS.
Delivery before 36 weeks was labelled
as cerclage failure.
After Univariate regression, it was
seen that CL and UCL was strongly associated with gestational age at birth.
UCL angle of 108 degree prior to 34 weeks
was a better predictor of preterm delivery than CL = 25 mm. Before28 weeks the
UCL angle of 112 degree had 100 sensitivity as compared to 29% that of CL.
Patients with UCA angle> 108 degree
had 35 times higher odds of spontaneous preterm birth (PTB) before 34 weeks while
the UCL > 112 degree conferred 42 times higher odds of delivering before 28 weeks.
The corresponding odds of delivery if
cervical length CL<25mm are 4.7 and OR 6.0 prior to 34 and 28 weeks
respectively.
The study cohort had 38% cerclage failure
rate and delivered at mean gestational age of 29 +/- 5.2 weeks compared to
those who delivered at 37.9 +/- 2.8 weeks (p<0.001).
A study presented at the 36th Annual
Pregnancy Meeting concluded that “A wide uterocervical angle ≥95 and ≥105
degrees detected during the second trimester was associated with an increased
risk for spontaneous preterm birth <37 and <34 weeks, respectively.
Uterocervical angle performed better than cervical length in this cohort.”[2]
The authors concluded that increasing
obtuse UCA signify increase chances of cerclage failure and give the
obstetrician valuable time to make arrangements for delivery at tertiary
center.
UCA performed better than CL as a
screening parameter for predicting preterm births (PTB) because of increased sensitivity
and NPV.
In fact, a combination of UCA and CL
synergistically can be best predictor of PTB in cerclage patients.
