Customized birthweight standards for a Spanish population.

OBJECTIVE: To analyse the biological factors affecting birthweight and to derive customized birthweight standards for a Spanish population. METHODS: A retrospective cohort was created with all the singleton pregnancies delivered at term and free of pathology in our Institution. Birthweight was modeled by multiple linear regression from maternal (ethnic origin, maternal height, booking weight, smoking, and parity), and fetal (gender, gestational age) characteristics. RESULTS: In addition to gestational age and sex, height, booking weight, ethnic origin, parity, and smoking all have significant and independent effects on birthweight. Women from East-Asia, Morocco and South-America had newborns on average 83 g, 74 g and 95 g heavier than White-European Spanish women. The effect of smoking was found to be dose-related. CONCLUSION: We found the relative effect of the maternal and fetal characteristics to be very similar to that reported in previous studies. We report coefficients for ethnic groups that account for a sizeable proportion of the population composition of several European countries.

Birth weight from pregnancies dated by ultrasonography in a multicultural British population.

OBJECTIVE: To produce standard curves of birth weight according to gestational age validated by ultrasonography in the British population, with particular reference to the effects of ethnic origin. DESIGN: Retrospective analysis of computerised obstetric database. SETTING: Three large maternity units associated with Nottingham University with over 16,000 deliveries a year. PATIENTS: 41,718 women with ultrasound dated singleton pregnancies and delivery between 168 and 300 days' gestation. MAIN OUTCOME MEASURES: Length of gestation, ethnic origin, parity, maternal height and weight at booking, smoking during pregnancy; the effect of these variables on birth weight. RESULTS: Birth weights from ultrasound dated pregnancies have a higher population mean and show less flattening of the birthweight curve at term than those of pregnancies dated from menstrual history. Significant differences were observed in mean birth weights of babies of mothers of European origin (3357 g), of Afro-Caribbean origin (3173 g), and from the Indian subcontinent (3096 g). There were also significant interethnic differences in length of gestation, parity, maternal height, booking weight, and smoking habit which affected birth weight. The ethnic differences in birth weight were even greater when the effect of smoking was excluded. CONCLUSIONS: Birthweight standards require precise dating of pregnancy and should describe the population from which they were derived. In a heterogeneous maternity population the accurate assessment of an individual baby's weight needs to take the factors which affect birthweight standards into consideration.

PIP: A new set of standard curves of birth weight for singleton pregnancies with gestational age dated by ultrasonography was generated for the British population. The source of data was a computerized obstetric database of 41,718 pregnancies delivered between 168 and 300 days' gestation, taken from 3 large maternity units in East Midlands, the Nottingham University and City Hospitals, and Derby City Hospital. There were significant differences between the birthweights of 37,336 babies of mothers of English-European origin (3357 gm), 1008 babies of Afro-Caribbean origin (3173 gm), and 1547 babies of Indian subcontinent origin (3096 gm). There were also significant differences between ethnic groups for gestational length, parity, maternal height, weight, and smoking. These differences were greater than smoking was controlled. The effect of smoking was dose-related: at 40 weeks' gestation mean birthweights were 3580 gm for nonsmokers, 3416 gm for 1-9 cigarettes daily, 3374 gm for 10-19 cigarettes daily, and 3377 gm, for over 20 cigarettes daily. About 30% of the European and Afro-Caribbean women smoker, but almost none of the east Indians did. As had been seen elsewhere, ultrasound dating showed a lower gestational age than did menstrual dating (276 vs. 279 days), a discrepancy that is most likely to be clinically relevant in postdate gestations. While ultrasound dating is much more accurate, ethnic origin must be taken into account when assessing individuals.