Prediction of size of infants at birth by measurement of symphysis fundus height.

Symphysis fundus heights (SF) were measured approximately 15 times during pregnancy in a consecutive series of 2941 women with regular menstrual cycles and known last menstrual period. A reference SF chart from 17 to 40 weeks of pregnancy was derived from measurements in 1350 of these women who were healthy, and heights and pre-pregnancy weights within the 10th and 90th centiles and were delivered vaginally of healthy infants with a birthweight/length ratio within +/- 2 SD. The reference chart was used to predict fetal growth deviations in the unselected series of pregnancies. The effectiveness of SF measures to detect fetuses with an infant birthweight/length ratio below -2 SD or a birthweight below the 10th centile was low; the sensitivity was only 16.7 and 26.6% and the predictive value of positive screening result was 1.8 and 18.0%, respectively. Corresponding values for fetuses with an infant birthweight/length ratio above + 2 SD or a birthweight above the 90th centile were 31.8 and 37.5% and 3.3 and 24.5%, respectively. Symphysis fundus (SF) measurement has thus been found to be of limited value as a screening method to detect abnormal size at birth.