PRB/NICHD Cervical Length Standard

To use the PRB/NICHD customized cervical length standard accompanying the manuscript:
Personalized assessment of cervical length improves prediction of spontaneous preterm birth: a standard and a percentile calculator, D. GUDICHA, R. ROMERO, D. KABIRI, E. HERNANDEZ-ANDRADE, P. PACORA, O. EREZ, J.P. KUSANOVIC, E. JUNG, C. PAREDES, S.M. BERRY, L. YEO, S.S. HASSAN, C.D. HSU, A.L. TARCA, AJOG, 2020, submitted.

you can use one of the options below:

  • Access our online calculator from here: CXLCalc

To install, load and use the CLcalc package, use these commands:

>install.packages(“CLcalc_0.1.0.tar.gz“,repos = NULL, type = “source”)


For help on how to use the function type:


A typical R session to use this package is shown below, where data is an input table with gestational ages (weeks), maternal weight (kg), height (cm), parity, and measured cervical lengths (mm). The output table includes the Percentile and also the cervical length quantiles for those maternal characteristics and gestational ages (5th, 10th, 50th, 90th, and 95th).