Trends in Preterm Delivery by Race

1. Trends in Preterm Delivery by Race The Effect of Data Editing Cheng Qin, Patty Dietz, Lucinda England, Joyce Martin, William Callaghan

2. Data and Study Population • Data: US Natality Files 1990 through 2002 • Study Population: Non-Hispanic White and Non-Hispanic African American singleton live births

3. Gestational Age Data Editing Methods Applied • Method 1: NCHS • Method 2: Alexander • Method 3: Zhang and Bowes • Method 4: LMP/CE

4. Alexander et al Method • Gestational age distributions were examined for births grouped into 125-g birth weight intervals • Gestational age values of ± 2.5 SD from the mean (about the first and 99th percentiles) were considered initially as cut points for implausible data • Statistically defined cut points were modified by a week or more in conjunction with clinical consultation • Birth records out of range were deleted

5. Zhang and Bowes Method • Normal probability plot of birth weight by gestational week • Cutoff point of birth weight selected when a plot from the current data began to deviate from the straight line systematically • Gestational age supplanted by CE for infants whose birth weight was greater than the cutoff point at a given gestational age • Cutoff point for 25 weeks applied to 20-24 weeks; no modification to records >35 weeks • Records with implausible birth weight/gestational age combinations and with missing CE excluded

6. LMP/CE Method • If NCHS ‘LMP’ and CE are within two weeks each other, use ‘LMP’; otherwise, use CE • Records with missing CE were deleted

7. Exclusion Criteria • California (no CE) • New Hampshire and Oklahoma from 1990 (no Hispanic) • Missing birthweight (0.1%) • Missing gestational age (0.3%) • Gestational age less than 20 weeks (0.03% in 2001)

8. Analysis • Percent of records excluded and substituted by different methods and the effect of data editing on bimodal distribution • PTD rates by race and methods 1990 through 2002 • Percent changes over time by methods and by gestational age stratum

9. Birthweight by Gestational Age Distribution 25-33 weeks – All Race Singleton Live Births, US 2001

10. Distribution of Singleton Live Births, US 2001

11. Percent of Records Excluded and Replaced by Methods, All Gestation, 1990 and 2002 NH white NH A-A NH white NH A-A 1990 2002

12. Percent of Records Excluded and Substituted by Methods, GA Groups– NH A-A 2002 20-27 wks 28-31 wks 32-36 wks

13. Birthweight Distribution 20-27 Weeks by Data Editing Methods, US NH white and NH A-A Singleton Live Births, 2001

14. Birthweight Distribution 28-31 Weeks by Data Editing Methods, US NH white and NH A-A Singleton Live Births, 2001

15. Birthweight Distribution 32-35 Weeks by Data Editing Methods, US NH white and NH A-A Singleton Live Births, 2001

16. Trend of PTD (<37 weeks) by Data Editing, Singleton Live Births for US NH white and NH A-A, 1990-2001

17. Percent Change of Preterm Delivery (<37 Weeks) NH white NH A-A

18. Summary • Bimodal distribution in early gestation weeks; disappeared when LMP/CE method was applied • Fixed second mode peaked around 3000 grams • Percent records excluded and replaced declined over time regardless of methods • PTD rates increased for NH whites regardless of the methods used • PTD rates slightly increased for NH A-A by LMP/CE, decreased by other methods

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