Table 3. Variables selected to be associated with MR/DD1 by backward elimination2 and parameter estimates by the GAM.
| Parametric terms | Level3 | Estimate4 | 95% Confidence Interval | P-value5 |
|---|---|---|---|---|
| Intercept | -1.408 | (-1.738, -1.077) | <0.001 | |
| Child gender | Female | -0.783 | (-0.916, -0.651) | <0.001 |
| Mother's race | African-American | 0.101 | (-0.037, 0.238) | 0.151 |
| Other | -0.750 | (-1.314, -0.187) | 0.009 | |
| SGA | Yes | 0.232 | (0.052, 0.412) | 0.011 |
| Parity | >= 1 | 0.288 | (0.156, 0.421) | <0.001 |
| Gestational age (weeks) | 28-36 | 0.271 | (0.088, 0.453) | 0.004 |
| < 28 | 1.432 | (0.749, 2.116) | <0.001 | |
| 2 | -0.085 | (-0.441, 0.270) | 0.638 | |
| 3 | 1.538 | (1.142, 1.934) | <0.001 | |
| Strip | 4 | 0.122 | (-0.238, 0.482) | 0.506 |
| 5 | 0.043 | (-0.336, 0.423) | 0.822 | |
| 6 | 0.663 | (0.227, 1.098) | 0.003 | |
| Smooth terms | Est. d.f. | Chi-Square | P-value6 | |
| Child age at last follow-up | 5.4 | 311.2 | <.001 | |
| As | 5.9 | 19.0 | 0.006 | |
*
AIC = 5597.5 (Akaike Information Criterion)
1
MR/DD: mental retardation or developmental delay.
2
The eliminated variables include alcohol use during pregnancy, mother's age at delivery, Hg and Pb.
3
The missing level of each categorical variable is the statistical reference group.
4
The exponential of the parameter estimate is interpreted as odd ratio.
5
P-value is based on t test.
6
P-value is based on Chi-square test.