Table 3.
Association between maternal and offspring preterm birth type in the population cohort a, Manitoba, Canada, 1980–2016
| Infant’s PTB cases/No of births | PTB rate, % | (N = 78,922) | (N = 78,922) | (N = 74,196) | (N = 39,478) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Offspring outcome | Maternal PTB type | URR | 95% CI | ARRb | 95% CI | ARRc | 95% CI | ARRd | 95% CI | ||
| Any PTB | Not Preterm | 4565/75,172 | 6.07 | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Spontaneous | 195/2165 | 9.01 | 1.48 | 1.29, 1.70 | 1.47 | 1.28, 1.68 | 1.43 | 1.24, 1.65 | 1.28 | 1.03, 1.58 | |
| Provider-initiated | 128/1585 | 8.08 | 1.33 | 1.12, 1.57 | 1.29 | 1.09, 1.52 | 1.23 | 1.02, 1.47 | 1.14 | 0.87, 1.48 | |
| Spontaneous PTB | Not Preterm | 3164/75,172 | 4.21 | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Spontaneous | 149/2165 | 6.88 | 1.64 | 1.40, 1.92 | 1.61 | 1.38, 1.89 | 1.57 | 1.32, 1.85 | 1.33 | 1.04, 1.71 | |
| Provider-initiated | 93/1585 | 5.87 | 1.39 | 1.14, 1.70 | 1.36 | 1.11, 1.66 | 1.32 | 1.07, 1.64 | 1.09 | 0.78, 1.52 | |
| Provider-initiated PTB | Not Preterm | 1401/75,172 | 1.86 | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Spontaneous | 46/2165 | 2.12 | 1.14 | 0.85, 1.52 | 1.13 | 0.85, 1.52 | 1.11 | 0.82, 1.51 | 1.16 | 0.76, 1.77 | |
| Provider-initiated | 35/1585 | 2.21 | 1.18 | 0.85, 1.65 | 1.13 | 0.81, 1.57 | 1.00 | 0.69–1.46 | 1.24 | 0.77, 1.99 | |
Abbreviations: PTB preterm birth, URR Unadjusted Relative Risk, ARR Adjusted Relative Risk, CI confidence intervals
aAnalyzed with a log-binomial regression model. 276 children excluded due to missing information on maternal PTB type
bAdjusted for whether mother moved or had a substance abuse diagnosis in year before birth of child, child’s birth year, mother’s age at birth of child, neighborhood location and SES at birth of child, child’s sex and child’s birth order
cRestricted to births 2000–2016 with complete information on additional covariates. Adjusted for whether mother moved or had a substance abuse diagnosis in year before birth of child, child’s birth year, mother’s age at birth of child, neighborhood location and SES at birth of child, child’s sex, child’s birth order, mother’s smoking status during pregnancy, mother’s education, inadequate prenatal care, receipt of employment income assistance in the year before the birth of the child, and whether mother had a partner
dRestricted to one randomly child per mother (1995–2016). Adjusted for whether mother moved or had a substance abuse diagnosis in year before birth of child, child’s birth year, mother’s age at birth of child, neighborhood location and SES at birth of child, child’s sex and child’s birth order