Introduction:
There is a growing body of evidence supporting the role of customized growth charts in improving detection of fetal growth restriction (FGR) and decreasing false positive diagnoses. The aim of the study is to produce a customised birthweight standard for Poland.

Material and methods:
Maternal height and weight, ethnicity, gestational age, weight and sex at birth as well as pre-existing and gestational complications were collected. Coefficients were derived using a backwards stepwise multiple regression technique. Smallness for gestational age by the customised standard was compared with the in-use Fenton standard in assessing risk of adverse outcomes using relative risk with 95% confidence intervals.

Results:
Data from 4,270 pregnancies were used as the study cohort. Fenton and customised SGA rates were 6.6% and 11.9%, respectively. The customised standard identified more cases that were at significantly increased risk of stillbirth, admission to neonatal intensive care or other neonatal complications, many of which were missed by the Fenton standard.

Conclusions:
The analysis confirmed the physiological variables that affect birthweight in studies from other countries and was able to quantify additional pathological factors of high maternal age and pregnancy-induced hypertension. Comparison with the Fenton standard showed that adverse outcomes associated with SGA birthweight are better identified by the customised standard in a Polish population.