BIRTH-WEIGHT FROM PREGNANCIES DATED BY ULTRASONOGRAPHY IN A MULTICULTURAL BRITISH POPULATION

Objective-To produce standard curves of birth weight according to gest ational age validated by ultrasonography in the British population, wi th particular reference to the effects of ethnic origin. Design-Retros pective analysis of computerised obstetric database. Setting-Three lar ge maternity units associated with Nottingham University with over 16 000 deliveries a year. Patients-41718 women with ultrasound dated sing leton pregnancies and delivery between 168 and 300 days' gestation. Ma in outcome measures-Length of gestation, ethnic origin, parity, matern al height and weight at booking, smoking during pregnancy; the effect of these variables on birth weight. Results-Birth weights from ultraso und dated pregnancies have a higher population mean and show less flat tening of the birthweight curve at term than those of pregnancies date d from menstrual history. Significant differences were observed in mea n birth weights of babies of mothers of European origin (3357 g), of A fro-Carribean origin (3173 g), and from the Indian subcontinent (3096 g). There were also significant interethnic differences in length of g estation, parity, maternal height, booking weight, and smoking habit w hich affected birth weight. The ethnic differences in birth weight wer e even greater when the effect of smoking was excluded. Conclusions-Bi rthweight standards require precise dating of pregnancy and should des cribe the population from which they were derived. In a heterogeneous maternity population the accurate assessment of an individual baby's w eight needs to take the factors which affect birthweight standards int o consideration.