Composite Morphometric/Morphographic Ultrasound Parameters of the Second Trimester Cervix for the Prediction of Spontaneous Preterm Labor

Abstract

BACKGROUND
There is need for simple, cheap and highly predctive test for spontaneous preterm labor (SPL). The
"zone of endocervical crypts (ZEC)" is a well-defined sonographic landmark corresponding to
enfolding of the endocervical mucosa. Early loss of ZEC might be considered as indicative of
“premature effacement”. We tested the efficacy of a "composite" parameter of cervical length plus
ZEC loss for the prediction SPL.
MATERIAL/METHODS
The study included singleton pregnant women attending Asyout Clinic for Gynecology and
Obstetrics between 20 and <24 weeks’ gestation.
Transvaginal ultrasonography was used for:
a) measuring the cervical length, and, b) detecting the existence/non-existance of ZEC.
* Cervical lengthwas measured as the distance between the internal os of the cervix and the
external os.
* The Zone of Endocervical Crypts (ZEC) was defined as the heteroechoic area around the
cervical canal (CC). Monoechoic appearance of the cervix was described as loss of the ZEC.
The sensitivity, specificity, positive and negative predictive values (PPV, NPV) were calculated
for: 1) cervical shortening 2) ZEC loss, 3) combined 1 & 2, and, 4) funneling
RESULTS
Two thousand and one pregnancies were evaluated for the incidence and sonographic prediction of
SPL (24 - <32 weeks, and 32-36 weeks).
The overall SPL rate was 9%.
Loss of ZEC, and, the combined ZEC loss with shortened cervix were found to have better
specificity and better PPV than the cervical shortening alone.
ZEC loss had better PPV for early rather than late PL.
“Funneling” had poor PPV, but, is still a good “negative”
CONCLUSION
The composite parameter of the “lost ZEC” and short cervix is superior to the cervical length alone
for the early prediction of SPL. Wider scale study is now being run for: a) ensuring the
reproducibility of the parameter testing values, and b) to find any correlation between the ZEC loss
and other clinical criteria as subtle infection.