Area-level poverty and preterm birth risk: a population-based multilevel analysis.
BACKGROUND
Preterm birth is a complex disease with etiologic influences from a variety of social, environmental, hormonal, genetic, and other factors. The purpose of this study was to utilize a large population-based birth registry to estimate the independent effect of county-level poverty on preterm birth risk. To accomplish this, we used a multilevel logistic regression approach to account for multiple co-existent individual-level variables and county-level poverty rate.


METHODS
Population-based study utilizing Missouri's birth certificate database (1989-1997). We conducted a multilevel logistic regression analysis to estimate the effect of county-level poverty on PTB risk. Of 634,994 births nested within 115 counties in Missouri, two levels were considered. Individual-level variables included demographics factors, prenatal care, health-related behavioral risk factors, and medical risk factors. The area-level variable included the percentage of the population within each county living below the poverty line (US census data, 1990). Counties were divided into quartiles of poverty; the first quartile (lowest rate of poverty) was the reference group.


RESULTS
PTB < 35 weeks occurred in 24,490 pregnancies (3.9%). The rate of PTB < 35 weeks was 2.8% in counties within the lowest quartile of poverty and increased through the 4th quartile (4.9%), p < 0.0001. High county-level poverty was significantly associated with PTB risk. PTB risk (< 35 weeks) was increased for women who resided in counties within the highest quartile of poverty, adjusted odds ratio (adj OR) 1.18 (95% CI 1.03, 1.35), with a similar effect at earlier gestational ages (< 32 weeks), adj OR 1.27 (95% CI 1.06, 1.52).


CONCLUSIONS
Women residing in socioeconomically deprived areas are at increased risk of preterm birth, above other underlying risk factors. Although the risk increase is modest, it affects a large number of pregnancies.
DeFranco
Emily A
EA
Department of Obstetrics and Gynecology, Washington University School of Medicine, St, Louis, Missouri, USA. defranee@ucmail.uc.edu
Lian
Min
M
Muglia
Louis A
LA
Schootman
Mario
M
D005260:Female; D005843:Geography; D005865:Gestational Age; D006801:Humans; D016015:Logistic Models; D008923:Missouri / Q000453:epidemiology; D016017:Odds Ratio; D011203:Poverty / Q000706:statistics & numerical data; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000191:economics*; D047928:Premature Birth / Q000453:epidemiology*; D012307:Risk Factors; D012959:Socioeconomic Factors; D016387:Women's Health
Biometrics. 2000 Sep;56(3):909-14
10985236
J Matern Fetal Neonatal Med. 2007 Aug;20(8):605-11
17674278
Ann N Y Acad Sci. 2008;1136:80-5
17954684
West J Nurs Res. 2007 Apr;29(3):284-300
17420521
Am J Obstet Gynecol. 2007 Sep;197(3):264.e1-6
17826413
BJOG. 2004 Feb;111(2):160-3
14723754
Am J Public Health. 2003 Jul;93(7):1137-43
12835199
J Epidemiol Community Health. 2003 Aug;57(8):550-2
12883048
Am J Epidemiol. 2008 Jan 15;167(2):155-63
17989062
J R Soc Med. 1995 Nov;88(11):611-5
8544143
Am J Public Health. 1997 Aug;87(8):1278-9
9279261
Am J Obstet Gynecol. 2006 Dec;195(6):1557-63
17014813
Am J Epidemiol. 2005 Jan 1;161(1):81-8
15615918
Am J Obstet Gynecol. 2007 Feb;196(2):131.e1-6
17306652
Am J Public Health. 2001 Nov;91(11):1808-14
11684609
Am J Public Health. 1997 Apr;87(4):597-603
9146438
Am J Obstet Gynecol. 2007 Aug;197(2):152.e1-7
17689630
Soc Sci Med. 2008 Jan;66(2):255-9
17920176
Am J Public Health. 2001 Nov;91(11):1815-24
11684610
Bull World Health Organ. 1987;65(5):663-737
3322602
Am J Epidemiol. 2002 Sep 1;156(5):471-82
12196317
J Epidemiol Community Health. 2006 Dec;60(12):1053-9
17108301
Ann Epidemiol. 1994 Jul;4(4):271-8
7921316
Natl Vital Stat Rep. 2006 Dec 28;55(11):1-18
17432301
Am J Obstet Gynecol. 2006 Sep;195(3):643-50
16949395
J Natl Cancer Inst. 2002 Jun 19;94(12):904-15
12072544
Semin Reprod Med. 2007 Jan;25(1):40-51
17205422
Int J Epidemiol. 2002 Jun;31(3):600-13
12055162
Obstet Gynecol. 2007 Aug;110(2 Pt 1):325-9
17666607