TABLE 2—
Risk Factors for Autism Diagnosis and Associations With ART and All Covariates for Unadjusted and 3 Adjusted Models Estimated on Analysis Subset (n = 2 420 330): California 1997–2007
| Crude: Unadjusted, HRR (95% CI) | Model 1: Adjusted for Demographics, HRR (95% CI) | Model 2: Model 1 + Mother’s Age, Parity, HRR (95% CI) | Model 2 + Pathway Factors, HRR (95% CI) | |
| ART effect | 1.790 (1.636, 1.959) | 1.713 (1.551, 1.892) | ||
| For mothers aged 20–34 y | 1.736 (1.457, 2.069) | 1.210 (1.011, 1.448) | ||
| For mothers aged ≥ 35 y | 1.365 (1.209, 1.541) | 1.002 (0.881, 1.139) | ||
| Birth year | ||||
| 1997 | 0.666 (0.619, 0.717) | 0.668 (0.621, 0.719) | 0.679 (0.631, 0.731) | |
| 1998 | 0.709 (0.660, 0.761) | 0.711 (0.662, 0.764) | 0.721 (0.671, 0.774) | |
| 1999 | 0.771 (0.719, 0.827) | 0.773 (0.720, 0.828) | 0.782 (0.729, 0.838) | |
| 2000 | 0.850 (0.794, 0.909) | 0.851 (0.795, 0.910) | 0.858 (0.802, 0.918) | |
| 2001 | 0.914 (0.855, 0.977) | 0.915 (0.856, 0.979) | 0.919 (0.860, 0.983) | |
| 2002 (Ref) | 1.000 | 1.000 | 1.000 | |
| 2003 | 1.049 (0.983, 1.121) | 1.046 (0.979, 1.117) | 1.044 (0.978, 1.115) | |
| 2004 | 1.038 (0.970, 1.110) | 1.033 (0.966, 1.105) | 1.027 (0.960, 1.098) | |
| 2005 | 1.072 (1.001, 1.147) | 1.066 (0.996, 1.141) | 1.054 (0.984, 1.128) | |
| 2006 | 1.080 (1.006, 1.160) | 1.070 (0.996, 1.149) | 1.064 (0.990, 1.143) | |
| 2007 | 1.187 (1.101, 1.281) | 1.177 (1.092, 1.270) | 1.171 (1.085, 1.263) | |
| Male infant | 4.710 (4.524, 4.904) | 4.710 (4.524, 4.904) | 4.678 (4.493, 4.871) | |
| Mother is college graduate | 1.085 (1.050, 1.121) | 1.009 (0.976, 1.0430) | 1.013 (0.980, 1.047) | |
| Mother’s race/ethnicity | ||||
| Non-Hispanic White (Ref) | 1.000 | 1.000 | 1.000 | |
| Black | 1.431 (1.341, 1.527) | 1.470 (1.378, 1.568) | 1.416 (1.327, 1.511) | |
| Asian | 1.114 (1.062, 1.168) | 1.124 (1.072, 1.180) | 1.118 (1.065, 1.173) | |
| Hispanic | 1.012 (0.970, 1.055) | 1.062 (1.018, 1.107) | 1.053 (1.010, 1.098) | |
| Other | 1.012 (0.970, 1.055) | 1.249 (0.999, 1.560) | 1.232 (0.986, 1.540) | |
| Mother is foreign-born | 1.143 (1.099, 1.189) | 1.129 (1.086, 1.174) | 1.129 (1.085, 1.1740) | |
| Primiparous | 1.338 (1.297, 1.380) | 1.335 (1.294, 1.3780) | ||
| Complications of pregnancy and delivery on the causal pathway | ||||
| Multiple birth | 1.418 (1.304, 1.5410) | |||
| Small for gestational age | 1.110 (1.057, 1.1660) | |||
| Preterm (< 37 wk) | 1.181 (1.124, 1.240) | |||
| Maternal diabetes | 1.276 (1.173, 1.3870) | |||
| Hypertension or preeclampsia | 1.115 (1.027, 1.2110) | |||
| Cesarean delivery | 1.272 (1.231, 1.3140) | |||
| −2Log L | 498 555.79 | 490 104.63 | 489 471.22 | 488 900.48 |
| AIC | 498 557.79 | 490 140.63 | 489 513.22 | 488 954.48 |
Note. AIC = Aikake information criterion; ART = assisted reproductive technology; CI = confidence interval; HRR = hazard risk ratio. We calculated the effect of ART for all mothers aged ≥ 20 y for crude and adjusted model 1. Model 1 includes demographic factors: year of birth, infant’s gender, and mother’s education and race. The estimated effect of ART is reported separately for mothers aged 20–34 and ≤ 35 y for models 2 and 3 because of the presence of an interaction. Model 2 includes all variables in model 1 plus factors associated with both ART and autism that might have an underlying biological impact on pregnancy health and fetal development: maternal age and parity and an interaction between mother’s age and ART. Model 3 includes all variables in model 2 plus perinatal outcomes previously associated with both ART and autism: multiple birth, preterm delivery, small for gestational age, maternal diabetes, pregnancy hypertension or preeclampsia, and cesarean delivery. Estimates for baseline categories are omitted.