Reference ranges of uterine artery pulsatility index from first to third trimester based on serial Doppler measurements: longitudinal cohort study

Abstract

What are the novel findings of this work?This study provides reference ranges of the mean uterine artery pulsatility index (UtA-PI) in a low-risk population from 10 + 0 to 39+ 0 gestational weeks, based on longitudinal prospective collection of serial Doppler measurements modeled in a multilevel framework with a rigorous methodology that has been validated in similar settings. What are the clinical implication of this work?Given the importance of UtA-PI as a marker for abnormal pregnancy outcomes related to placental dysfunction, it is crucial to provide reference ranges for clinical use that are based on high-quality data and rigorous statistical modeling in a low-risk population.

Re: Reference ranges of uterine artery pulsatility index from first to third trimester based on serial Doppler measurements: longitudinal cohort study

“…Histogram of delta values of mean uterine artery pulsatility index (UtA‐PI) obtained by two certified sonographers in 22 074 unselected pregnancies at 11 + 0 to 41 + 3 weeks' gestation with respect to reference values of median according to Cavoretto et al 1 …”

“…Based on this framework, when we attempted to apply the equation provided by Cavoretto et al 1 ,. we identified the μ T (mean), the σ T (coefficient of variation) and the γ T (skewness) parameters of the model; however, we could not find the specification to the δ T kurtosis parameter from the θ exponential transformation of the modulus exponential normal (MEN) model 2 .…”

“…We read with great interest the study of Cavoretto et al which provides gestational-age (GA)-specific reference ranges for mean uterine artery (UtA) pulsatility index (PI) based on longitudinal data assessment throughout pregnancy 1 . The UtA-PI curves were constructed using a parametric method developed by Royston and Wright 2 , which is more adequate than the standard statistical techniques 3 , however, it requires the use of a software script 4 due to more complex modeling.…”

Reply

“…We thank Drs Oviedo‐Cruz and Carrasco‐Blancas for their Correspondence about our recent analysis 1 , which gives us the opportunity to further elucidate the highly complex methods employed to establish reference ranges for mean uterine artery pulsatility index (UtA‐PI) according to gestational age (GA) using the method described by Royston and Wright 2 . We are grateful to the authors for endeavoring to validate our model and apologize that further clarification is required to facilitate this.…”

“…According to the method described by Royston and Wright 2 the corresponding Z ‐score is obtained by the following formula: where: x = observed value of UtA‐PI at a given GA; X_ml = mean expected value of UtA‐PI at the same given GA (obtained from our published equation 1 ); SD_ml = standard deviation of the mean at the same given GA (obtained from our published equation 1 ); G_ml = −0.353959888219833; D_ml = 1.22444927692413.…”