CLINICAL AND ULTRASOUND PREDICTION OF MACROSOMIA IN DIABETIC PREGNANCY

Objective To study prospectively the prediction power, at different ge stations, of clinical and ultrasound measurements for fetal size in di abetic pregnancy. Setting A large combined obstetric diabetic clinic i n a teaching hospital. Participants One hundred and eighty-one pregnan cies in which women had scans at least two of three specific time poin ts and who were delivered of singletons after 34 weeks: 73% were pre-g estational insulin-dependent diabetics, the others were pre-gestationa l White class A or gestational diabetics. Interventions Clinical estim ates of fundal height and fetal size and ultrasound estimates of abdom inal circumference and head circumference were routinely carried out a t gestational ages of 28, 34 and 38 weeks or before delivery. Main out come measures Standardised birthweight, corrected for gestation and pa rity. The relation with clinical and ultrasound measurements was inves tigated using multiple linear regression and the capability of the mea surements to predict macrosomic births (>95th centile of normals) usin g receiver-operator characteristic curves. Results All measurements ar e poor predictors of eventual standardised birthweight. Prediction imp roves with closeness to delivery. Prediction is significantly improved by adding ultrasound to clinical information, but at 34 weeks or late r this only contributes 8% of the variance. There is no difference in the prediction power for macrosomia between clinical and ultrasound me asurements. Conclusions Even regular serial scanning and clinical exam ination will not always diagnose the macrosomic fetus in diabetic preg nancy. In our hands, clinical examination is as predictive as ultrasou nd measurements. Ultrasound does add to clinical prediction power but only to a small extent. Ultrasound should be used in a selected way, a s defined by clinical findings, and with recognition and understanding of the errors and biases involved.