BMC Public Health 2005, 5:79 http://www.biomedcentral.com/1471-2458/5/79 Table 4: Underlying causes of post-neonatal death by maternal age (n = 180). Maternal age (years) 12–17 18–19 20–35 Accidental n (%) 8(15) 11 (17) 4(6) SIDS/ respiratory arrest n (%) 16(31) 34 (52) 22 (35) Perinatal/ congenital n (%) 12 (23) 9(14) 16 (26) chi-square = 14.3, p = 0.08 Cause of death (%) Infectious n (%) All other n (%) Total n (%) 4(8) 1(2) 2(3) 12 (23) 11 (17) 18 (29) 52 (100) 66 (100) 62 (100) Table 3 includes the results of the logistic regression model. Race, appropriate education level, marital status, parity, smoking during pregnancy, level of prenatal care and participation in Medicaid, WIC, or food stamp pro- grams significantly affected the primary effect of maternal age on infant mortality risk and were included in the final model. Controlling for these variables, the risk for neona- tal and post-neonatal mortality was 1.43 (CI 0.98, 2.08) and 1.73 (CI 1.14, 2.64), respectively, for the youngest adolescent mothers. There was no increased risk of neonatal or post-neonatal mortality for older adolescent mothers. Furthermore, adjusting for gestational age did not appreciably change any of the adjusted OR for the pri- mary effect of age on infant mortality. First-order interactions between covariates and age, considered as a block, did not reach significance and were dropped from subsequent analyses. Of particular interest was the differential effect of the pov- erty construct in the model on neonatal and post-neona- tal mortality risks. Poverty was defined by participation in Medicaid, WIC and/or food stamp programs, and the effect of such programs appeared to be strongly protective against neonatal mortality when controlling for maternal age, but a significant risk factor for post-neonatal mortal- ity. Mothers participating in the food stamps program (our "poorest" category) had a reduced risk of neonatal mortality (OR 0.36, CI 0.25, 0.53) compared to mothers who did not participate in any of the poverty assistance programs. However, their risk of post-neonatal mortality (OR 2.29, CI 1.36, 3.86) was significantly higher. Stratify- ing the post-neonatal deaths by cause of death appears to show a higher percentage of deaths due to accidents or infections for the youngest mothers compared to older mothers in our study population (Table 4). Discussion We conclude that neonatal mortality rates do not differ by maternal age, but post-neonatal rates may be higher for mothers aged 12–17 years after adjusting for socioeconomic and other known risk factors. Our results are most similar to Reichman and Pagnini, who studied all New Jersey births in 1989 and 1990 [18]. They found that controlling for medical and socioeconomic factors accounted for some, but not all the effect of young mater- nal age on infant mortality. The unadjusted odds ratio of infant mortality among white 15–17 year olds in their study was 2.5; the adjusted value was 1.6. Their study was strengthened by access to linked uniform billing hospital discharge records in addition to state vital statistics. They were therefore able to assess socioeconomic status much more directly in their model, comparing Medicaid recipi- ents and "self-pay" to the privately insured. In our study, we were limited to inferring poverty status by the dichotomous values of participation in WIC, Medic- aid, or food stamps programs as noted on the birth certif- icate. Recognizing the eligibility criteria for these programs (130% of federal poverty level for food stamps and less than 185% of poverty level for WIC and Medic- aid) allowed us to predict confidently income levels of program participants, but we cannot conclude that those who are not participants are of higher income levels. Par- ticularly in the aftermath of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996, many individuals who were eligible may not have enrolled in such programs. Nevertheless, 75–80% of the two younger maternal cohorts were enrolled in Medicaid and/or WIC, compared to only 36% of the older mothers. Such dra- matic differences are likely to be truly related to socioeco- nomic distinctions and not bureaucratic or regulatory obstacles unique to older women. This study is also lim- ited by the validity of the original data entered on birth and death certificates. Of particular concern would be the possibility of differential bias in reporting of information between older and younger mothers since there is evi- dence that reporting infant mortality may suffer from a racial bias and the race distributions are not identical in our age cohorts [19]. Our finding that participation in WIC and Medicaid appears to be protective against neonatal mortality is con- Page 5 of 7 (page number not for citation purposes)