Table 1. Clinical characteristics.
| Term births | SPTB-IM | P | SPTB-PPROM | P | |
| Maternal Characteristics | 2953 | 96 | 60 | ||
| Age | 28.0 (5.8) | 27.6 (6.5) | 0.50 | 28.0 (5.8) | 0.90 |
| BMI | 25.6 (5.3) | 26.1 (5.5) | 0.35 | 25.2 (6.0) | 0.58 |
| Height (cm) | 165.2 (6.6) | 164.5 (6.9) | 0.26 | 163.3 (6.7) | 0.023 |
| Head circumference (cm) | 56.0 (1.7) | 55.9 (1.4) | 0.47 | 55.5 (1.6) | 0.019 |
| Systolic BP (mmHg) | 108 (11) | 108 (10) | 0.95 | 107 (11) | 0.55 |
| Diastolic BP (mmHg) | 65 (8) | 66 (8) | 0.31 | 65 (8) | 0.86 |
| Caucasian | 2558 (86.6) | 90 (93.6) | 0.048 | 52 (86.7) | 0.99 |
| First born | 1708 (58.1) | 42 (44.2) | 0.66 | 15 (25.0) | 0.01 |
| Social Characteristics | |||||
| SEI | 40.674 (16.5) | 39.5 (17.3) | 0.51 | 40.3 (15.1) | 0.87 |
| Full-time employment | 1972 (66.8) | 58 (60.4) | 0.19 | 44 (73.3) | 0.29 |
| Diet Characteristics | |||||
| Smoking (15 weeks) | 313 (10.6) | 22 (22.9) | 0.000 | 9 (15.0) | 0.28 |
| Marijuana (pre-preg) | 191 (6.5) | 17 (17.7) | 0.000 | 5 (8.3) | 0.57 |
| Marijuana (1st trimester) | 31 (1.0) | 8 (8.3) | 0.000 | 2 (3.3) | 0.11 |
| Psychological Characteristics | |||||
| Anxiety Index >90% | 211 (7.2) | 12 (12.6) | 0.049 | 6 (10.0) | 0.41 |
| Not feeling better than ever | 2275 (77.5) | 83 (86.5) | 0.04 | 48 (80.0) | 0.64 |
| Obstetric Characteristics | |||||
| Gravidity | 1.3 (0.6) | 1.6 (0.8) | 0.000 | 1.4 (0.6) | 0.54 |
| Months to conceive | 5.9 (11.6) | 7.4 (11.9) | 0.23 | 11.9 (22.1) | 0.000 |
| < = 3 months to conceive | 1871 (63.6) | 51 (53.1) | 0.038 | 31 (51.7) | 0.06 |
| Donor sperm | 141 (4.8) | 5 (5.2) | 0.84 | 8 (13.3) | 0.004 |
| Hormonal treatment | 90 (3.0) | 2 (2.1) | 0.59 | 7 (11.7) | 0.001 |
| Mild Hypertension (not on treatment) | 29 (1.0) | 2 (2.1) | 0.30 | 3 (5.0) | 0.007 |
| LLETZ | 107 (3.6) | 7 (7.3) | 0.07 | 7 (11.7) | 0.002 |
| >1 Vaginal bleeding | 145 (4.9) | 9 (9.4) | 0.05 | 4 (6.7) | 0.54 |
| APH | 162 (5.5) | 23 (24.0) | 0.000 | 5 (8.6) | 0.31 |
| Waking at night | |||||
| Once | 918 (31.2) | 27 (28.1) | 0.10 | 13 (21.7) | 0.014 |
| ≥2 times | 1837 (62.5) | 59 (61.5) | 0.13 | 39 (65.0) | 0.07 |
| Cervical length (mm) | 41.0 (7.4) | 38.7 (7.9) | 0.006 | 38.9 (6.9) | 0.047 |
| Average UTRI >90% | 240 (7.5) | 17 (18.1) | 0.002 | 7 (12.7) | 0.27 |
| Average UTRI | 0.56 (0.09) | 0.59 (0.12) | 0.002 | 0.57 (0.09) | 0.29 |
| Family History | |||||
| Gestational diabetes | 106 (3.6) | 8 (8.3) | 0.020 | 5 (8.3) | 0.062 |
| Recurrent GDM | 19 (0.6) | 2 (2.1) | 0.11 | 2 (3.3) | 0.027 |
| Preeclampsia | 284 (9.6) | 20 (20.8) | 0.000 | 5 (8.3) | 0.74 |
| Mother had preeclampsia | 233 (7.9) | 16 (16.7) | 0.003 | 4 (6.7) | 0.73 |
| Gestational Hypertension | 6 (0.2) | 0 (0.0) | 0.98 | 1 (1.7) | 0.051 |
| Miscarriage (mother) | 888 (30.1) | 28 (29.2) | 0.85 | 10 (16.7) | 0.028 |
| Diabetes Type 2 (mother) | 137 (4.6) | 9 (9.4) | 0.037 | 2 (3.3) | 0.63 |
| Low birthweight baby* | 27 (0.9) | 5 (5.2) | 0.000 | 1 (1.7) | 0.55 |
| Birth Outcomes | |||||
| Gestational age 40 (1) | 34 (4) | 0.97 | 33 (5) | 0.97 | |
| Birthweight (g) | 3481 (472) | 2378 (736) | 0.000 | 2379 (761) | 0.000 |
| Customized centile | 49 (29) | 49 (31) | 0.85 | 51 (32) | 0.50 |
| SGA | 285 (10) | 11 (11.5) | 0.56 | 6 (10) | 0.93 |
Characteristics as mean (SD) or n (%); head circumference and height in centimetres; x mother/sister with low birth weight baby; APH = antepartum haemorrhage; BP = blood pressure; UTRI = uterine artery resistance index.