| Period 1 | Period 2 | p | |
|---|---|---|---|
| November 2015-March 2018 | August 2018-August 2022 | ||
| (n = 79) | (n = 82) | ||
| Treatment for preventing and preparing preterm delivery | |||
| Ritodrine hydrochloride | |||
| Intravenous | 79 (100.0) | 0 (0.0) | <0.001 |
| Oral | 9 (11.4) | 0 (0.0) | 0.001 |
| Vaginal progesterone | 0 (0.0) | 82 (100.0) | <0.001 |
| Intravenous magnesium sulphate | 31 (39.2) | 14 (17.1) | 0.003 |
| Oral calcium channel blockers | 2 (2.5) | 4 (4.9) | 0.682 |
| Antenatal steroid treatment | 28 (35.4) | 15 (18.3) | 0.020 |
| Maternal and delivery characteristics | |||
| Maternal age (years) | 32.0 (29.0-35.0) | 32.5 (29.0-36.0) | 0.723 |
| Multiparity | 46 (58.2) | 45 (54.9) | 0.751 |
| Race (nationality): Asian (Japanese) | 79 (100.0) | 82 (100.0) | NA |
| Body mass index | 20.3 (18.4-22.0) | 20.2 (19.2-22.4) | 0.431 |
| Infertility treatment | 9 (11.4) | 20 (24.4) | 0.040 |
| GA at maternal treatment start (weeks) | 30.9 (28.8-31.7) | 28.9 (26.8-30.7) | <0.001 |
| CL at maternal treatment start (mm) | 22.0 (12.5-31.0) | 16.0 (11.3-19.0) | 0.001 |
| Previous preterm delivery | 12 (15.2) | 14 (17.1) | 0.832 |
| Cervical cerclage | 5 (6.3) | 2 (2.4) | 0.271 |
| History of cervical conization | 3 (3.8) | 2 (2.4) | 0.678 |
| Cesarean section | 36 (45.6) | 25 (30.5) | 0.053 |
| Histological chorioamnionitis | 25 (31.6) | 19 (23.2) | 0.289 |
| Period 1 | Period 2 | p | |
|---|---|---|---|
| November 2015-March 2018 | August 2018-August 2022 | ||
| (n = 79) | (n = 82) | ||
| GA at birth (weeks) | 36.6 (32.3-37.6) | 38.2 (36.2-39.1) | <0.001 |
| Preterm delivery (<37 weeks) | 43 (54.4) | 24 (29.3) | 0.001 |
| Preterm delivery (<34 weeks) | 26 (32.9) | 13 (15.9) | 0.016 |
| Interval from the diagnosis of short cervix to delivery <14 days | 26 (32.9) | 7 (8.5) | <0.001 |
| Interval from the diagnosis of short cervix to delivery <28 days | 30 (38.0) | 11 (13.4) | 0.001 |
| Birth weight (kg) | 2.43 (1.83-2.96) | 2.85 (2.41-3.18) | 0.002 |
| Male | 43 (54.4) | 44 (53.7) | 1.000 |
| 1 min Apgar score | 8.0 (7.0-8.0) | 8.0 (8.0-8.0) | 0.480 |
| 5 min Apgar score | 9.0 (8.0-9.0) | 9.0 (8.3-9.0) | 0.184 |
| Umbilical artery pH <7.10 | 0 (0.0) | 1 (1.2) | 1.000 |
| Umbilical artery BE <−10.0 | 0 (0.0) | 3 (3.7) | 0.246 |
| NICU admission | 39 (49.4) | 32 (39.0) | 0.207 |
| Neonatal | |||
| Intubation | 14 (17.7) | 5 (6.1) | 0.028 |
| Surfactant administration | 11 (13.9) | 4 (4.9) | 0.060 |
| Intraventricular hemorrhage | 1 (1.3) | 0 (0.0) | 0.491 |
| Death | 0 (0.0) | 1 (1.2) | 1.000 |
| Crude OR (CI) | Adjusted OR (CI) | |
|---|---|---|
| Primary outcomes | ||
| Preterm delivery (GA at birth <37 weeks) | 0.35 (0.18-0.66) | 0.43 (0.19-0.96) |
| Preterm delivery (GA at birth <34 weeks) | 0.38 (0.18-0.82) | 0.39 (0.13-1.21) |
| NICU admission | 0.66 (0.35-1.23) | 0.95 (0.42-2.15) |
| Secondary outcomes | ||
| Extension of pregnancy <14 days | 0.19 (0.08-0.47) | 0.21 (0.06-0.72) |
| Extension of pregnancy <28 days | 0.25 (0.12-0.55) | 0.25 (0.09-0.74) |
| Neonatal Intubation | 0.30 (0.10-0.88) | 0.17 (0.04-0.75) |
| Neonatal surfactant administration | 0.32 (0.10-1.04) | 0.19 (0.03-1.14) |
