Table 2. Pregnancy Outcomes in Users and Nonusers of Cannabis During Pregnancy in the Unmatched Cohort, BORN Ontario, 2012-2017.
| Outcome | No. of Events (% Risk) | Risk Difference, % (95% CI)a | Relative Risk (95% CI)a | |
|---|---|---|---|---|
| Nonusers (n = 652 190) | Cannabis Users (n = 9427) | |||
| Preterm birth, weeks’ gestation | ||||
| <37 | 39 955 (6.1) | 1134 (12.0) | 5.88 (5.22 to 6.54) | 1.96 (1.86 to 2.07) |
| 34-36 6/7 | 30 085 (4.7) | 791 (8.7) | 4.00 (3.41 to 4.58) | 1.86 (1.74 to 1.99) |
| 32-33 6/7 | 4026 (0.7) | 132 (1.6) | 0.90 (0.63 to 1.17) | 2.40 (2.01 to 2.86) |
| 28-31 6/7 | 2936 (0.5) | 124 (1.5) | 1.00 (0.73 to 1.27) | 3.09 (2.57 to 3.71) |
| <28 | 2908 (0.5) | 87 (1.0) | 0.57 (0.34 to 0.80) | 2.20 (1.77 to 2.73) |
| Maternal Outcomes | ||||
| Preeclampsia | 31 884 (4.9) | 393 (4.2) | −0.70 (−1.11 to −0.29) | 0.86 (0.78 to 0.94) |
| Gestational diabetes | 48 159 (7.4) | 398 (4.2) | −3.16 (−3.58 to −2.74) | 0.58 (0.52 to 0.63) |
| Delivery Type | ||||
| Cesarean | 179 472 (27.5) | 2213 (23.5) | −4.04 (−4.90 to −3.18) | 0.85 (0.82 to 0.88) |
| Assisted vaginal | 57 880 (8.9) | 828 (8.8) | −0.11 (−0.68 to 0.47) | 0.99 (0.93 to 1.06) |
| Perinatal Outcomes | ||||
| SGA (third percentile) | 15 856 (2.4) | 596 (6.3) | 3.91 (3.42 to 4.41) | 2.60 (2.40 to 2.82) |
| SGA (10th percentile) | 60 360 (9.3) | 1712 (18.2) | 8.96 (8.17 to 9.74) | 1.96 (1.88 to 2.05) |
| Placental abruption | 5359 (0.8) | 172 (1.8) | 1.02 (0.75 to 1.30) | 2.24 (1.92 to 2.60) |
| Stillbirth | 2500 (0.4) | 58 (0.6) | 0.23 (0.07 to 0.39) | 1.60 (1.24 to 2.08) |
| Neonatal Outcomes | ||||
| Transfer to NICU | 77 611 (11.9) | 2368 (25.1) | 13.19 (12.31 to 14.07) | 2.11 (2.04 to 2.19) |
| Apgar score <4 (5 min)b | 4615 (0.7) | 130 (1.4) | 0.68 (0.44 to 0.92) | 1.95 (1.64 to 2.32) |
Abbreviations: NICU, neonatal intensive care unit; SGA, small for gestational age.
a
Risk difference and relative risk adjusted for infant sex; standard errors account for repeated pregnancies within mothers.
b
Apgar scores from 0 to 10 assigned at 5 minutes after birth based on measures of heart rate, respiratory effort, skin color, muscle tone, and reflex irritability; lower scores indicate depressed vitality.16