Table 4.
Estimated Regression Coefficients and Marginal Effects in the Equations for Whether the Woman Began Prenatal Care in Her First Trimester
| Ordinary Least Squares† | Two-Stage Least Squares†‡ | Single Equation Logistic Model | Two-Equation Model with Terza Adjustment†‡ | |
|---|---|---|---|---|
| Number of observations | 38,174 | 38,943 | 38,174 | 38,174 |
| Coefficients (95% confidence interval) | ||||
| Insurance coverage before pregnancy (uninsured omitted category) | ||||
| Medicaid coverage | 0.102*** | — | 0.541*** | 0.836* |
| (0.070, 0.135) | (0.383, 0.699) | (−0.071, 1.744) | ||
| Predicted Medicaid coverage | — | 0.276 | — | — |
| (−0.463, 1.015) | ||||
| Predicted residuals, Medicaid equation | — | — | — | −0.317 |
| (–1.240, 0.607) | ||||
| Private insurance coverage | 0.129*** | — | 0.739*** | −0.484 |
| (0.107, 0.152) | (0.616, 0.862) | (−1.522, 0.554) | ||
| Predicted private insurance coverage | — | 0.149 | — | — |
| (−0.433, 0.731) | ||||
| Predicted residuals, private equation | — | — | — | 1.222** |
| (0.181, 2.263) | ||||
| Medicaid eligibility category (not eligible omitted) | ||||
| Welfare-related eligible | −0.016 | −0.066 | 0.043 | –0.134 |
| (−0.085, 0.053) | (−0.282, 0.150) | (−0.275, 0.361) | (−0.514, 0.245) | |
| Not eligible | 0.050*** | 0.058 | 0.400*** | 0.758*** |
| (0.019, 0.080) | (−0.088, 0.205) | (0.181, 0.619) | (0.422, 1.094) | |
| Postwelfare reform (prewelfare reform omitted) | 0.051** | 0.053** | 0.301** | 0.355*** |
| (0.012, 0.090) | (0.010, 0.097) | (0.063, 0.540) | (0.116, 0.594) | |
| Interaction terms (postwelfare reform × expansion-related eligible omitted) | ||||
| Postwelfare reform × welfare-related eligible | −0.005 | 0.020 | −0.022 | 0.043 |
| (−0.083, 0.074) | (−0.108, 0.148) | (−0.380, 0.335) | (–0.330, 0.417) | |
| Postwelfare reform × not eligible | −0.033** | −0.039** | −0.207* | −0.248** |
| (−0.065, −0.000) | (−0.077, −0.002) | (−0.445, 0.031) | (−0.487, −0.009) | |
| Marginal effect (95% confidence interval) in percentage point difference | ||||
| Insurance coverage before pregnancy (uninsured omitted category) | ||||
| Medicaid coverage | 10.2*** | 27.6 | 6.9*** | 9.7*** |
| (7.0, 13.5) | (−46.3, 101.5) | (5.1, 8.6) | (1.6, 17.8) | |
| Private insurance coverage | 12.9*** | 14.9 | 11.6*** | −6.8 |
| (10.7, 15.2) | (−43.3, 73.1) | (9.5, 3.6) | (−20.7, 7.2) | |
| Postwelfare reform (prewelfare reform omitted) | 5.1** | 5.3** | 4.6** | 5.5*** |
| (1.2, 9.0) | (1.0, 9.7) | (0.8, 8.5) | (1.6, 9.3) | |
| Interaction terms (postwelfare reform × expansion-related eligible omitted) | Mean marginal effect (range) in percentage point difference | |||
| Postwelfare reform × welfare-related eligible | −0.5 | 2.0 | −0.4 | 0.9 |
| (−8.3, 7.4) | (−10.8, 14.8) | (−0.5, −0.1) | (0.1, 1.3) | |
| Postwelfare reform × not eligible | −3.3** | −3.9** | −3.7* | −4.9* |
| (−6.5, −0.0) | (−7.7, −0.2) | (−5.2, −0.8) | (−6.5, −1.1) | |
Source: Regression run on data from the Pregnancy Risk Assessment Monitoring System (PRAMS) for Alaska, Florida, Maine, New York (excluding New York City), Oklahoma, South Carolina, Washington, and West Virginia for 1996–1999.
Notes:
p < 0.01
p < 0.05
p < 0.10.
Other independent variables in the equation include mother's age, race, and educational and marital status; whether she resided in a central city or fringe county of a large metropolitan area, another metropolitan area, or a nonmetropolitan area; whether the pregnancy was her first and whether it was intended; whether she drank, smoked, or was experiencing certain life stressors during pregnancy; whether she had any medical conditions putting the pregnancy at risk; the father's education status; the ratio of obstetricians to births in the county of residence; indicators for the state of residence; and a monthly time trend variable.
The first stage equation for both two-equation models was a multinomial logistic for whether the mother had Medicaid or private insurance coverage prior to becoming pregnant or whether she was uninsured. Besides the independent variables listed above, we also included the following variables as instrumental variables in this equation: the ratio of minimum wage to the maximum income to qualify for Medicaid; the percentage of single men in the state who were uninsured; whether the state had a cash diversion policy in its welfare program; and the annual percentage growth in households in the woman's county of residence, the county unemployment rate, and the interaction of the unemployment rate with the metropolitan designation of the county.