Interpretation
The reason why we comprehensively took all above factors into account to
build the model was that the predictive performance of single cervical
measurement is not satisfied.16, 25, 26 The mechanism
of PTB in twin maternity is subjected to various mechanical stimuli (two
continuously growing foetuses and the expanding uterus) and biochemical
stimuli (inflammatory factors, fetoplacental signals and steroid
hormones).35, 36 There seem to be structure-function
associations between SPTB and cervical microstructure, geometry, and
mechanical function, which are not fully understood.37Recently, researchers proposed a new conceptual framework for the theory
of PTB in which a maternal clinical phenotype potentially related to a
certain perinatal outcome is characterized by a series of common
clinical characteristics observed during pregnancy.27,
38 Demographic factors such as age, race, BMI, history of PTB, previous
uterine surgeries, smoking, and prevalence of PTB in that specific area
may indicate the initial states and variations in the cervix, including
geometry and mechanical function, which increase the risk of cervical
insufficiency. All these risk factors have their interconnected effects
and a computational framework in changing and remodelling the
cervix.39-42
However, it has been argued that maternal factors or cervix geometry
(including length) alone do not perform well in PTB risk assessment,
primarily due to poor sensitivity.16, 25, 26, 43 In
our study, we specifically investigated the role of cervical measurement
data and maternal demographic characteristics on SPTB probability at
< 32 weeks. By doing so, we have found that nulliparity,
monochorionicity, lower prepregnancy BMI, previous preterm birth or late
abortion, cervical funneling and shorter cervical length confers an
increased risk of PTB at <32 weeks and then build the
nomogram.
By our predition model, clinicians can counsel the patients and define
the follow-up schedule according to a patient’s individual risk of PTB.
Thus, the ability to identify patients at higher risk for SPTB will
assist us to schedule tighter follow-ups or administer targeted
interventions such as antenatal corticosteroid administration, tocolytic
therapy and transfer to a tertiary medical centre and reduce
overtreatment to those at lower risk. Further clinical trials are
warranted to validate and improve its diagnostic performance, and the
corresponding online calculator can be updated and serve as a basic
screening tool for clinical practice and subsequent research.