REFINEMENTS IN MANAGING MATERNAL WEIGHT ADJUSTMENT FOR INTERPRETING PRENATAL SCREENING RESULTS

This study examines the relationship between maternal weight and serum levels of alpha-fetoprotein, unconjugated oestriol, and human chorion ic gonadotropin in a population of 47 585 women being provided with pr enatal screening for Down's syndrome and open neural tube defects. The study population contains sufficient numbers of women at the extremes of weight to allow the determination that a reciprocal-linear equatio n more accurately describes the weight relationship for two of the thr ee analytes than the currently used log-linear equations. The reciproc al-linear equations, while more appropriate, provide only a minimal ad vantage over the log-linear equations. A more important finding is tha t published weight equations may not be optimal for some screening pro grammes, due to differences in the mean weight of the populations bein g tested. Screening programmes are encouraged to calculate their own w eight correction formulae, based on data from their own population, an d to monitor the mean maternal weight to detect when modifications in the weight correction formulae might be indicated.