Table 4.
Crude and Adjusted Odds Ratios and 95% Confidence Intervals of Gestational Week at Delivery of the Second Pregnancy in Association With Gestational Week at Delivery of the First Pregnancy by Delivery Subtypes
| Gestational Week at Delivery of the 1st Pregnancy |
Gestational Week at Delivery of the 2nd Pregnancy | |||
|---|---|---|---|---|
| Spontaneous | ||||
| Before 32 | 32–36 | 37–38 | 39 or More | |
| Spontaneous | ||||
| Before 32 | 43 (28.3) | 97 (10.8) | 23 (4.2) | 14 (3.1) |
| Crude OR (95% CI) | 41.8 (19.4–90.3) | 15.2 (8.3–27.7) | 2.5 (1.3–5.0) | |
| Adjusted OR (95% CI)† | 61.2 (24.1–155.3) | 12.0 (6.4–22.4) | 2.2 (1.1–4.6) | |
| 32–36 | 71 (46.7) | 517 (57.5) | 218 (40.1) | 85 (18.7) |
| Crude OR (95% CI) | 11.4 (6.4–20.2) | 13.3 (9.7–18.3) | 3.9 (2.8–5.4) | |
| Adjusted OR (95% CI)† | 11.6 (6.2–21.8) | 14.4 (10.3–20.0) | 4.1 (3.0–5.8) | |
| 37–38 | 20 (13.2) | 173 (19.2) | 141 (26) | 111 (24.4) |
| Crude OR (95% CI) | 2.5 (1.3–4.8) | 3.4 (2.5–4.7) | 1.9 (1.4–2.7) | |
| Adjusted OR (95% CI)† | 1.9 (0.9–4.1) | 3.3 (2.3–4.6) | 2.0 (1.4–2.7) | |
| 39 or more | 18 (11.8) | 112 (12.5) | 161 (29.7) | 245 (53.8) Reference |
| Medically indicated | ||||
| Before 32 | 0 (0) | 5 (0.3) | 2 (0.2) | 4 (0.3) |
| Crude OR (95% CI) | * | 1.4 (0.4–5.4) | * | |
| Adjusted OR (95% CI)† | * | 1.0 (0.3–3.9) | * | |
| 32–36 | 8 (3.5) | 83 (5.1) | 32 (2.9) | 9 (0.7) |
| Crude OR (95% CI) | 6.0 (2.3–15.6) | 10.7 (5.3–21.3) | 5.4 (2.6–11.3) | |
| Adjusted OR (95% CI)† | 5.3 (1.9–14.8) | 10.4 (5.2–21.0) | 5.4 (2.5–11.5) | |
| 37–38 | 50 (22.1) | 551 (34.2) | 315 (28.8) | 217 (16) |
| Crude OR (95% CI) | 1.5 (1.1–2.2) | 2.9 (2.5–3.5) | 2.2 (1.8–2.7) | |
| Adjusted OR (95% CI)† | 1.3 (0.9–1.9) | 2.8 (2.4–3.4) | 2.1 (1.7–2.6) | |
| 39 or more | 168 (74.3) | 974 (60.4) | 744 (68.1) | 1,125 (83) Reference |
| Gestational Week at Delivery of the 2nd Pregnancy | |||
|---|---|---|---|
| Medically Indicated | |||
| Before 32 | 32–36 | 37–38 | 39 or More |
| 3 (30) | 21 (14.4) | 96 (4.4) | 152 (3.2) |
| * | 10.2 (5.8–18.0) | 2.3 (1.8–3.1) | |
| 9.8 (5.4–17.7) | 2.3 (1.7–3.0) | ||
| 3 (30) | 64 (43.8) | 790 (35.9) | 995 (20.9) |
| * | 4.8 (3.1–7.3) | 2.9 (2.6–3.3) | |
| 4.7 (3.0–7.1) | 3.0 (2.7–3.4) | ||
| 2 (20) | 26 (17.8) | 609 (27.7) | 1,013 (21.3) |
| * | 1.9 (1.1–3.2) | 2.2 (2.0–2.5) | |
| 1.9 (1.1–3.2) | 2.2 (2.0–2.6) | ||
| 2 (20) | 35 (24) | 703 (32) | 2,595 (54.6) Reference |
| 1 (2.1) | 5 (0.9) | 30 (0.2) | 61 (0.2) |
| * | 7.16 (2.86–17.91) | 1.5 (1.0–2.3) | |
| * | 5.76 (2.28–14.55) | 1.4 (0.9–2.1) | |
| 2 (4.3) | 31 (5.4) | 428 (2.9) | 596 (1.6) |
| * | 4.5 (3.1–6.6) | 2.2 (1.9–2.5) | |
| * | 4.2 (2.9–6.1) | 2.1 (1.9–2.4) | |
| 10 (21.3) | 174 (30.5) | 3,897 (26.5) | 5,696 (15) |
| 1.6 (0.8–3.3) | 2.7 (2.2–3.2) | 2.1 (2.0–2.2) | |
| 1.6 (0.8–3.2) | 2.5 (2.1–3.0) | 2.0 (1.9–2.1) | |
| 34 (72.3) | 361 (63.2) | 10,345 (70.4) | 31,512 (83.2) Reference |
OR, odds ratio; CI, confidence interval.
Data are n (%) unless otherwise specified.
Not computed as a result of frequency less than 5.
Adjusted for maternal and obstetric factors in both pregnancies (maternal age, education, mother’s birthplace, Medi-Cal for delivery, smoking, pre-existing and gestational hypertension with or without preeclampsia, pre-existing and gestational diabetes, urinary tract infection, anemia, drug abuse, and mental disorder), maternal race or ethnicity, cesarean delivery at the first pregnancy, interpregnancy interval, and paternity change between.