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Abstract

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. All coefficients of our modulus exponential normal (MEN) model were calculated, and we are happy to provide here the additional data required for generalized implementation of our chart.The following coefficients are estimated for the mean of our UtA-PI data: skewness = +1.059472; kurtosis = +2.895564; SD = +0.3865211; variance = +0.1493886. However, according to the work of Royston and Wright 2 , the coefficients above are not valid for calculation of Z-scores from the MEN model. In our work, the xriml module in STATA software (Stata-Corp. LLC, College Station, TX, USA) was used to perform analyses related to the MEN model 3 . We fitted non-normally distributed data to a normal model smoothed with second-degree fractional polynomial by using the constant parameters termed G_ml (non-normal skewness) and D_ml (non-normal kurtosis). The estimated G_ml = −0.353959888219833 and D_ml = 1.22444927692413 are intrinsic to the published formulas 1 . 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.We hope that knowledge of these parameters and coefficients will facilitate the use of our UtA-PI reference ranges in clinical practice.

Comparative evaluation of gestosis score vs uterine artery pulsatility index in predicting gestational hypertension: A study protocol

“…Gestational hypertension is a major medical problem during pregnancy, with possible adverse implications on both mother's and fetal health. [2][3][4] It is critical to predict and identify high-risk pregnancies early to provide proper monitoring and care. The pooled prevalence of Hypertensive disorders of pregnancy (HDOP) in India is 9% (95% CI, 8%-10%), which is significantly higher than the global prevalence, as reported in a study done in pregnant women of the Indian population.…”