Table 3. Frequency and Adjusted Risk Ratios (ARRs) of Maternal Outcomes by Frequency of Prenatal Cannabis Use.
| Maternal outcomes by frequency of prenatal cannabis use | Pregnancies, No. (%) | aRR (95% CI)a |
|---|---|---|
| Metabolic outcomes | ||
| Hypertensive disordersb | ||
| Gestational hypertension | ||
| Daily | 402 (22.3) | 1.24 (1.14-1.36) |
| Weekly | 475 (21.3) | 1.21 (1.11-1.31) |
| Monthly or less | 838 (18.0) | 1.03 (0.97-1.10) |
| Never | 40 541 (14.3) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 2107 (20.7) | 1.21 (1.16-1.25) |
| Preeclampsia | ||
| Daily | 129 (7.2) | 1.15 (0.96-1.36) |
| Weekly | 147 (6.6) | 1.11 (0.95-1.30) |
| Monthly or less | 253 (5.4) | 0.89 (0.79-1.01) |
| Never | 13 166 (4.6) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 683 (6.7) | 1.14 (1.06-1.24) |
| Eclampsia | ||
| Daily | 3 (0.2) | 1.11 (0.35-3.49) |
| Weekly | 5 (0.2) | 1.53 (0.61-3.85) |
| Monthly or less | 8 (0.2) | 1.13 (0.54-2.35) |
| Never | 350 (0.1) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 18 (0.2) | 1.13 (0.69-1.83) |
| Gestational diabetesc | ||
| Daily | 149 (7.8) | 0.99 (0.85-1.15) |
| Weekly | 160 (6.9) | 0.87 (0.75-1.00) |
| Monthly or less | 341 (7.1) | 0.88 (0.79-0.98) |
| Never | 34 853 (11.9) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 871 (8.1) | 0.89 (0.83-0.95) |
| Gestational weight gaind | ||
| Less than guidelines | ||
| Daily | 281 (46.0) | 1.05 (0.96-1.14) |
| Weekly | 340 (46.6) | 1.09 (1.01-1.18) |
| Monthly or less | 658 (42.7) | 1.04 (0.98-1.10) |
| Never | 45 390 (38.5) | 1 [Reference] |
| Unknown frequency, positive toxicology results | 1448 (46.3) | 1.04 (1.00-1.08) |
| Greater than guidelines | ||
| Daily | 1230 (78.8) | 1.06 (1.03-1.09) |
| Weekly | 1481 (79.2) | 1.07 (1.04-1.09) |
| Monthly or less | 3070 (77.6) | 1.06 (1.04-1.08) |
| Never | 163 753 (69.3) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 7364 (81.4) | 1.11 (1.10-1.12) |
| Placental outcomes | ||
| Placenta previa | ||
| Daily | 17 (0.9) | 1.10 (0.68-1.77) |
| Weekly | 26 (1.1) | 1.38 (0.93-2.04) |
| Monthly or less | 43 (0.9) | 1.06 (0.78-1.44) |
| Never | 3330 (1.1) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 83 (0.8) | 0.93 (0.74-1.16) |
| Placental abruption | ||
| Daily | 29 (1.5) | 1.26 (0.87-1.84) |
| Weekly | 29 (1.2) | 1.07 (0.74-1.55) |
| Monthly or less | 74 (1.5) | 1.31 (1.03-1.67) |
| Never | 3721 (1.3) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 149 (1.4) | 1.15 (0.98-1.37) |
| Placenta accretae | ||
| Daily | 4 (0.2) | 1.51 (0.54-4.22) |
| Weekly | 5 (0.2) | 1.60 (0.64-4.04) |
| Monthly or less | 7 (0.1) | 1.10 (0.51-2.38) |
| Never | 462 (0.2) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 21 (0.2) | 1.36 (0.85-2.16) |
| Severe maternal morbidity | ||
| Daily | 76 (3.9) | 1.00 (0.80-1.26) |
| Weekly | 77 (3.3) | 0.88 (0.70-1.10) |
| Monthly or less | 180 (3.7) | 1.00 (0.86-1.16) |
| Never | 9620 (3.2) | 1 [Reference] |
| Unknown frequency, positive toxicology result | 385 (3.5) | 0.97 (0.87-1.07) |
Modified Poisson models with robust standard errors were adjusted for maternal sociodemographic characteristics (age category, race and ethnicity, neighborhood deprivation index), parity, birth year, prenatal care initiation, prepregnancy body mass index category, other noncannabis prenatal substance use (alcohol, nicotine, opioids, stimulants, and anxiety/sleep medications), and maternal medical and mental health comorbidities (pregestational diabetes, nausea/vomiting during pregnancy, mood/anxiety disorders, other psychiatric disorders, substance use disorders [other than cannabis], and antidepressant use).
Pregnancies of individuals with chronic hypertension were excluded (n = 14 187).
Pregnancies of individuals with pregestational diabetes were excluded. In addition, gestational diabetes could not be ascertained for pregnancies ending in therapeutic abortion. A total of 4737 pregnancies were excluded. Pregestational diabetes was not included as a covariate.
Categories determined by the 2009 Institute of Medicine guidelines. Pregnancies with missing weight values were excluded (n = 15 863). Less than guidelines models were fit among pregnancies less than or within guidelines; greater than guidelines models were fit among pregnancies greater than or within guidelines.
Placenta accreta could only be ascertained for pregnancies that were delivered in a Kaiser Permanente Northern California facility and ended in live birth or stillbirth (alive at admission); 10 979 were excluded.