Table 3.
Frequencies and adjusted odds ratios for preterm birth by antenatal model of care and psychosocial risk characteristics, British Columbia, April 1, 2008-December 31, 2012
| Preterm birth by model of care | ||||||
|---|---|---|---|---|---|---|
| MW n = 3394 | GP n = 25,753 | OB n = 4746 | MW vs. GP | MW vs. OB | GP vs. OB | |
| n(%) | n(%) | n(%) | aOR (95% CI) | aOR (95% CI) | aOR (95% CI) | |
| Mental illnessa | ||||||
| Yes | 56/1011 (5.54) | 344/4917 (7.00) | 71/545 (13.03) | 0.92 (0.68–1.24) | 0.49 (0.34–0.72) | *0.54 (0.41–0.71) |
| No | 98/2383 (4.11) | 1257/20,836 (6.03) | 352/4201 (8.38) | 0.73 (0.59–0.91) | 0.51 (0.41–0.65) | 0.70 (0.61–0.79) |
| Substance useb | ||||||
| Yes | 8/152 (5.26) | 215/2276 (9.45) | 39/182 (21.43) | 0.59 (0.29–1.21) | *0.24 (0.11–0.54) | *0.41 (0.28–0.61) |
| No | 146/3242 (4.50) | 1386/23,477 (5.90) | 384/4564 (8.41) | 0.80 (0.67–0.96) | 0.55 (0.45–0.68) | 0.69 (0.61–0.79) |
| Teen mother | ||||||
| Yes (14–19 yrs.) | 9/117 (7.69) | 187/2584 (7.24) | 21/206 (10.19) | 1.09 (0.55–2.19) | 0.74 (0.33–1.66) | 0.67 (0.42–1.09) |
| No (25–29 yrs.) | 46/1161 (3.96) | 475/7705 (6.16) | 100/1371 (7.29) | 0.69 (0.50–0.94) | 0.56 (0.39–0.80) | 0.81 (0.65–1.02) |
| Social assistancec | ||||||
| Yes | 17/239 (7.11) | 299/3617 (8.27) | 61/534 (11.42) | 0.89 (0.53–1.50) | 0.63 (0.36–1.12) | 0.71 (0.53–0.96) |
| No | 137/3155 (4.34) | 1302/22,136 (5.88) | 362/4212 (8.59) | 0.78 (0.64–0.94) | 0.51 (0.42–0.63) | 0.66 (0.58–0.75) |
| Neigh. SEPd | ||||||
| Low/Medium | 135/2944 (4.59) | 1429/22,915 (6.24) | 397/4369 (9.09) | 0.80 (0.66–0.96) | 0.52 (0.42–0.64) | 0.65 (0.58–0.74) |
| High | 19/450 (4.22) | 172/2838 (6.06) | 26/377 (6.90) | 0.72 (0.44–1.17) | 0.63 (0.34–1.17) | 0.88 (0.57–1.36) |
| Mental illness, substance use | ||||||
| Both | 5 or less /95e | 95/927 (10.25) | 18/76 (23.68) | 0.43 (0.15–1.19) | *0.18 (0.06–0.55) | *0.41 (0.23–0.74) |
| Neither | 94/2325 (4.04) | 1134/19,438 (5.83) | 331/4090 (8.09) | 0.73 (0.59–0.91) | 0.52 (0.41–0.66) | 0.71 (0.62–0.81) |
| Mental illness, social assistance | ||||||
| Both | 7/128 (5.47) | 117/1195 (9.79) | 27/161 (16.77) | 0.58 (0.26–1.32) | 0.35 (0.14–0.86) | 0.60 (0.38–0.96) |
| Neither | 88/2272 (3.87) | 1075/18,414 (5.84) | 318/3828 (8.31) | 0.70 (0.56–0.88) | 0.48 (0.37–0.61) | 0.68 (0.59–0.79) |
| Substance use, social assistance | ||||||
| Both | 5 or less /45e | 94/832 (11.30) | 22/93 (23.66) | 0.78 (0.27–2.27) | 0.34 (0.11–1.10) | 0.44 (0.26–0.76) |
| Neither | 133/3047 (4.36) | 1178/20,643 (5.71) | 345/4118 (8.38) | 0.78 (0.65–0.95) | 0.53 (0.43–0.65) | 0.67 (0.59–0.77) |
Abbreviations: MW midwife, GP general practitioner, OB obstetrician, OR odds ratio, CI confidence interval
aMental illness included any of the following diagnoses prior to, or during the current pregnancy: anxiety disorder, depression, postpartum depression, bipolar disorder, other/unknown (including schizophrenic, mood, and psychotic disorders). Aside from mild anxiety or depression, a physician would diagnose mental illness
bSubstance use included any indication in the medical record of heroin/opioids, cocaine, methadone, solvents, marijuana or other/unknown drugs used by the mother at any time during pregnancy, as well as prescription or other drug use identified as a risk by the provider
cSocial assistance recipients received public financial assistance during the year of delivery due to low income
dNeighbourhood low/medium socioeconomic position included women residing in the four lowest income quintiles, depending on residential postal code at delivery
ePercentage suppressed due to small cell size
*Outcomes had statistically significant tests of interaction (p < 0.10) comparing difference of effect across strata (yes vs. no)
Models adjusted for all variables listed except stratifying variables: maternal age, medical risk, obstetric risk, pre-pregnancy BMI, infant sex, receipt of social assistance, smoking status, substance use, mental illness/disorder, neighbourhood SEP, Local Health Area socioeconomic rank, and northern residence
Odds ratios based on 2178 PTB births and 33,893 total births with no missing information for this analysis