P13.08: Comparison of reference charts for estimated fetal weight and for actual birth weight

Abstract

24–30 day cycle. The influence of fetal gender, maternal smoking and maternal height on gestational age (GA) at the time of CRL measurement was assessed using chi-square test. 4,595 deliveries were spontaneous and 1,299 induced (missing information in 31 cases). The relative risk (RR) of preterm delivery (≤258 days) using LMP and CRL was estimated for girls compared with boys in women with a spontaneous delivery. Results: The table shows the distribution of the difference between GA by LMP and GA by CRL on fetal gender, maternal smoking and maternal height. In non-smoking women the RR of preterm delivery was unchanged in girls compared with boys when comparing CRL (RR 0.81) to LMP (RR 0.79). In smoking women, however, the RR of preterm delivery increased from 0.50 by LMP to 0.80 by CRL. In tall women the RR increased from 0.38 using LMP to 0.54 using CRL, while the RR was unchanged in women < 173 cm. Conclusions: Fetal gender, maternal smoking and maternal height significantly influence gestational dating by CRL. Using CRL will overestimate GA in tall non-smoking women with a male fetus and underestimate GA in short, smoking women with a female fetus. The effect of the three parameters is additive. P13.08 Comparison of reference charts for estimated fetal weight and for actual birth weight