Back to Annual Meeting Page		American Public Health Association 133rd Annual Meeting & Exposition December 10-14, 2005 Philadelphia, PA

Abstract #114420

Michael J. Davidoff, MPH¹, Todd Dias, MS¹, Tomoko Kushnir, BS¹, Rebecca Russell, MSPH¹, Siobhan M. Dolan, MD², Karla Damus, RN, PhD¹, Nancy Green, MD², and Joann Petrini, PhD, MPH¹. (1) Perinatal Data Center, March of Dimes Birth Defects Foundation, 1275 Mamaroneck Ave, White Plains, NY 10605, 914.994.4549, mdavidoff@marchofdimes.com, (2) March of Dimes, 1275 Mamaroneck Avenue, White Plains, NY 10605

As preterm birth rates have increased, more emphasis has been placed on gestational age-specific morbidities. The purpose of this study was to describe the changing distribution of singleton births by gestational age in the U.S. from 1992-2002 and to assess the impact on gestational age-specific birthweight.

Retrospective analyses were conducted using NCHS birth certificate data. Singleton live births were stratified by mode of delivery (vaginal/cesarean). When stratified by individual week of gestation, the majority of vaginal births in 1992 (24.2%) were born at 40 weeks. In 2002, this majority shifted to 39 weeks (25.3%). While the majority of cesarean births were born at 39 weeks throughout the study, the proportion increased from 23.5% to 25.0%. Analyses were also stratified by gestational age categories (<32,32-34,35-36,37-39,40,40+). While the percent of births born at 41+ and 40 weeks decreased between 1992 and 2002 (30.5% and 10.3%, respectively), the percent of infants born at 37-39 weeks and 35-36 weeks increased (21.4% and 14.5%, respectively). The majority of this change remained after adjusting for maternal age/race/ethnicity. Among vaginal births, mean birthweight between 1992 and 2002 decreased at all individual weeks of gestation between 17-36 weeks, increased between 37-39 weeks, and decreased >39 weeks. Among cesarean deliveries, mean birthweight increased among infants born between 36-38 weeks, while decreasing among all other gestational ages. Despite a left shift in the distribution of gestational age, mean birthweight increased among gestational age categories with the largest proportional increase (36-39 weeks) within the distribution. Implications for outcomes will be discussed.

Learning Objectives:

• Describe changes in the distribution of gestational age and gestational age-specific birthweight in the United States.
• Assess the impact of maternal age and race/ethnicity on this changing distribution.
• Identify the potential impact on prematurity-related morbidities and hospital costs.

Keywords: Pregnancy Outcomes, MCH Epidemiology

Presenting author's disclosure statement:

I wish to disclose that I have NO financial interests or other relationship with the manufactures of commercial products, suppliers of commercial services or commercial supporters.