To evaluate the value of using symphysis-fundus (SF) distance and maternal weight gain measurements in predicting an infant's birth weight, these measurements were analysed in 831 single-birth deliveries at Aker University Hospital during a period of 3 months. Of the 96 babies with a birth weight below the 10th percentile for gestational age, 39 (41%) could be detected by a series of SF-measurements. For every third correctly identified SGA (small for gestational age) baby, there were 7 false positive predictions. Only 13 (14%) of the mothers who gave birth to SGA babies demonstrated a weight gain at each medical check-up during pregnancy, whereas 197 (30%) of the women giving birth to normal-weight babies showed a weight gain each time (p = 0.02). However, for maternal weight gain, both predictive value (14%) and specificity (29%) were low. Hence, these two screening methods for the detection of SGA babies remain imprecise in practice. Test procedures should be improved, and factors influencing fetal growth should be emphasized to detect fetuses at risk.