Table 4 Maternal demographic characteristics recorded on birth certificates of northern California samplesa
| Â | Northern California Family Cohort | ||||
|---|---|---|---|---|---|
| Â | Source population | Contacted | Tier I | Tier II | Tier III |
Number of households | 11,850 | 1,955 | 499 | 186 | 30 |
Age | Â | *b | *b | Â | Â |
   Mean | 28.7 | 30.8 | 31.6 | 31.7 | 30.3 |
Age group | Â | *b | *b | Â | Â |
   Under 25 years | 27.8% | 17.2% | 13.4% | 11.3% | 16.7% |
   25-34 years | 52.4% | 53.9% | 53.3% | 58.1% | 56.7% |
   35-44 years | 19.5% | 28.3% | 33.1% | 30.1% | 26.7% |
   45+ | 0.3% | 0.6% | 0.2% | 0.5% | 0.0% |
Education level | Â | *b | *b | **c | Â |
   0-8 years | 8.3% | 7.2% | 4.6% | 0.5% | 0.0% |
   9-11 years | 12.8% | 10.4% | 6.4% | 1.6% | 6.7% |
   12 years | 25.9% | 16.3% | 12.6% | 12.4% | 10.0% |
   13-15 years | 19.9% | 20.2% | 21.0% | 22.0% | 10.0% |
   16 years | 17.7% | 23.7% | 24.6% | 26.3% | 33.3% |
   >16 years | 15.4% | 22.3% | 30.7% | 37.1% | 40.0% |
Race/ethnicity d | Â | *b | *b | Â | Â |
   White | 71.0% | 71.3% | 80.0% | 79.6% | 93.3% |
   Asian | 20.2% | 23.6% | 15.6% | 16.2% | 6.7% |
   African American | 6.5% | 3.5% | 3.6% | 3.2% | 0.0% |
   Native American | 0.7% | 0.3% | 0.2% | 0.5% | 0.0% |
   Other/Missing | 1.6% | 1.3% | 0.6% | 0.5% | 0.0% |
Hispanic identification | Â | *b | *b | **c | Â |
   Latino | 33.2% | 24.1% | 21.6% | 11.9% | 23.1% |
   Non-Latino | 66.5% | 75.6% | 78.2% | 87.6% | 76.9% |
   Missing | 0.3% | 0.3% | 0.2% | 0.5% | 0.0% |
Place of birth | Â | *b | *b | **c | Â |
   USA | 55.3% | 56.8% | 68.5% | 76.3% | 80.0% |
   Mexico | 18.4% | 13.9% | 10.6% | 2.7% | 6.7% |
   Other | 26.2% | 29.2% | 20.6% | 21.0% | 13.3% |
   Missing | 0.1% | 0.1% | 0.2% | 0.0% | 0.0% |
Publicly funded delivery | Â | *b | *b | Â | Â |
   Yes | 33.6% | 21.5% | 17.0% | 8.6% | 13.3% |
   No | 66.2% | 78.4% | 82.6% | 91.4% | 86.7% |
   Missing | 0.2% | 0.2% | 0.4% | 0.0% | 0.0% |