Are very low birthweight births among American Indians and Alaska Natives underregistered?
BACKGROUND
International infant mortality rates vary widely. This variation has been attributed to many factors, including differential reporting. In the US, American Indians and Alaska Natives (AI/AN), who generally have low socioeconomic status, have a low neonatal mortality rate. One possible explanation is underregistration of very low birthweight (VLBW, < 1,500 g) births. We hypothesized that underregistration may occur disproportionately among AI/AN residing on or near reservations (areas controlled by an American Indian group). We estimated infant mortality in these areas.


METHODS
Linked birth-infant death files for 1989-1991 were used to compare VLBW and neonatal mortality among AI/AN infants in counties with reservations with those in non-reservation counties. The VLBW rates for non-reservation counties were applied to the reservation risk distribution to calculate directly adjusted VLBW and neonatal mortality rates for reservation counties. This method assumes that greater registration in non-reservation counties yields a more accurate estimate of the relationship between risk factors and outcomes.


RESULTS
Despite a higher prevalence in reservation counties of risk factors, the reported VLBW rate was 0.84% in reservation and 1.17% in non-reservation counties. The neonatal mortality rate was 5.4 per 1,000 in reservation counties and 6.0 in non-reservation counties. Direct adjustment yielded a VLBW rate of 1.28% (95% CI: 1.14-1.39) and a neonatal mortality rate of 6.7-9.8 per 1,000 in reservation counties.


CONCLUSIONS
Reported neonatal mortality among AI/AN may understate the true rate due to underregistration of VLBW births. Direct adjustment may be useful in estimating infant mortality rates for populations with incomplete vital registration.
Heck
K E
KE
National Center for Health Statistics, Hyattsville, MD 20782, USA.
Schoendorf
K C
KC
Parker
J
J
D017677:Age Distribution; D000413:Alaska / Q000453:epidemiology; D004522:Educational Status; D005313:Fetal Death / Q000453:epidemiology; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data*; D007226:Infant Mortality; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D004930:Inuit / Q000706:statistics & numerical data*; D015995:Prevalence; D012042:Registries / Q000706:statistics & numerical data*; D012307:Risk Factors; D015996:Survival Rate; D014481:United States / Q000453:epidemiology