AN EVALUATION OF THE PREVALENCE AND POTENTIAL ADVERSE OUTCOMES OF MACROSOMIA IN THE MIDWIFERY POPULATION OF NORTHERN AMERICA

Abstract

Background and Objectives: To date, no research has examined the prevalence and management of suspected fetal macrosomia in midwifery care, which may provide an alternative approach to cesarean section and induction with improvements in maternal and infant outcomes. The objectives of this study were to 1) determine the prevalence of fetal macrosomia and adverse outcomes that may result from a macrosomic birth in the MANAstats database; 2) identify the maternal characteristics which predict macrosomia; 3) determine the adverse maternal and infant outcome differences among macrosomic and normal weight infants in the MANAstats database. Methods: We analyzed 10,011 midwifery reported pregnancy and birth records from midwives across North America from January 2007- December 2009. After excluding for certain high-risk criteria, we compared the prevalence and adverse outcomes associated with macrosomic infants (4000-4499 grams, 4500-4999 grams, and >5000 grams) to non-macrosomic infants who weighed 3000-3000 grams. Results: The prevalence of macrosomia according to >4000 grams criteria was 24.7% and >4500 grams 5.53%. Maternal risk factors for macrosomia included: Caucasian race, married, maternal age between 15-34 years, and a gestational length greater than 40 weeks. The proportion of obstetric and infant complications showed a progressive and significant increase among the macrosomic birth weight categories with the highest risk at >5000 grams. The risk of shoulder dystocia (4000-4449-g infants: odds ratio, 4.08 [95% CI, 3.27-5.09]; 4500-4999-g infants: odds ratio, 8.31 [95% CI, 6.20-11.14]; and >5000-g infants: odds ratio, 29.92 [95% CI, 17.42-51.39]) and 5-minute Apgar scores 5000-g infants: odds ratio, 10.23 [95% CI, 2.32-45.13]) posed the highest risk in comparison to previous research on this topic. The prevalence of cesarean section among all groups was less than 9% and not found to be statistically significant by birthweight group. Conclusion: It is unclear if the risks shoulder dystocia and 5-minute Apgar scores < 3 outweigh the risks of prophylactic cesarean section on perceived macrosomic infants without jeopardizing maternal and infant health. Until further research regarding the risk versus benefit of alternatives to macrosomic vaginal birth, we recommend that strategies to prevent Grades II and III macrosomia need to be incorporated into the midwifery model of care.