Table 3.
Risk of Preterm Birth (Before 32 Weeks of Gestation and 32–36 Weeks of Gestation) and Early Term Birth (37–38 Weeks of Gestation) in the Second Pregnancy by Gestational Week at Birth in the First Pregnancy
| Gestational Week at Delivery of the 2nd Pregnancy |
Gestational Week at Delivery of the 1st Pregnancy | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Before 32 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 or More |
|
| Sample (n) | 935 | 334 | 556 | 1,166 | 2,130 | 4,246 | 10,180 | 25,837 | 118,505 |
| Before 32 | 58 (6.2) | 12 (3.6) | 8 (1.4) | 22 (1.9) | 25 (1.2) | 39 (0.9) | 59 (0.6) | 112 (0.4) | 367 (0.3) |
| 23.4 (17.2–31.8) | 16.0 (8.6–29.8) | 6.6 (3.2–13.7) | 9.0 (5.7–14.0) | 5.4 (3.6–8.1) | 4.4 (3.1–6.1) | 2.6 (1.9–3.4) | 1.7 (1.4–2.1) | ||
| 32–36 | 154 (16.5) | 46 (13.8) | 95 (17.1) | 181 (15.5) | 260 (12.2) | 449 (10.6) | 799 (7.8) | 1,287 (5.0) | 2,928 (2.5) |
| 9.2 (7.6–11.2) | 9.0 (6.4–12.5) | 11.8 (9.2–15.0) | 10.1 (8.5–12.0) | 7.4 (6.4–8.5) | 6.5 (5.9–7.3) | 4.5 (4.1–4.9) | 2.5 (2.4–2.7) | ||
| 37–38 | 273 (29.2) | 124 (37.1) | 219 (39.4) | 432 (37.0) | 801 (37.6) | 1,726 (40.7) | 4,092 (40.2) | 9,490 (36.7) | 26,744 (22.6) |
| 1.9 (1.6–2.2) | 2.6 (2.1–3.3) | 3.1 (2.5–3.7) | 2.7 (2.4–3.1) | 2.6 (2.3–2.8) | 2.8 (2.7–3.0) | 2.6 (2.5–2.7) | 2.1 (2.0–2.2) | ||
| 39 or more | 450 (48.1) | 152 (45.5) | 234 (42.1) | 531 (45.5) | 1,044 (49.0) | 2,032 (47.9) | 5,230 (51.4) | 14,948 (57.9) | 88,466 (74.7) Reference |
Data are n (%) or adjusted odds ratio (95% confidence interval) unless otherwise specified.
Adjusted for maternal and obstetric factors in both pregnancies (maternal age, education, mother’s birth place, 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.