TABLE 1.
Baseline maternal characteristics.
| Control (39 + 0 to 40 + 6 weeks) | sPTD <34 + 0 weeks | sPTD <32 + 0 weeks | sPTD <30 + 0 weeks | sPTD <28 + 0 weeks | |
|---|---|---|---|---|---|
| Variable | n = 205 | n = 61 | n = 27 | n = 17 | n = 8 |
| Maternal age at delivery (years) | 31.7 (4.3) | 31.4 (4.7) | 30.6 (5.1) | 31.7 (4.3) | 27.8 (4.6) |
| Ethnicity | |||||
| White | 190 (92.7%) | 55 (90.2%) | 23 (85.2%) | 14 (82.4%) | 6 (75.0%) |
| Black | 1 (0.5%) | 2 (3.3%) | 2 (7.7%) | 2 (11.8%) | 2 (25.0%) |
| Mixed White Black | 3 (1.4%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Middle East | 4 (1.9%) | 2 (3.3%) | 1 (3.8%) | 1 (5.9%) | 0 (0.0%) |
| India | 2 (1.0%) | 1 (1.7%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Southeast Asian | 1 (0.5%) | 1 (1.7%) | 1 (3.8%) | 0 (0.0%) | 0 (0.0%) |
| Other | 4 (1.9%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Maternal country of birth | |||||
| Sweden | 160 (86.5%) | 43 (91.4%) | 15 (71.4%) | 9 (64.3%) | 3 (50.0%) |
| Other European | 17 (9.1%) | 2 (4.3%) | 4 (19.0%) | 3 (21.4%) | 1 (16.7%) |
| Outside Europe | 8 (4.3%) | 2 (4.3%) | 2 (9.5%) | 2 (14.3%) | 2 (33.3%) |
| Highest level of education | |||||
| 9 years | 3 (1.7%) | 5 (10.0%) | 3 (14.3%) | 2 (14.3%) | 2 (33.3%) |
| 12 years | 38 (21.5%) | 12 (24.0%) | 6 (28.6%) | 4 (28.6%) | 2 (33.3%) |
| >12 years | 134 (76.6%) | 33 (66.0%) | 12 (57.1%) | 8 (57.1%) | 2 (33.3%) |
| Main occupation | |||||
| Employed | 154 (82.8%) | 42 (80.8%) | 16 (76.2%) | 9 (64.3%) | 2 (33.3%) |
| Student | 13 (6.9%) | 5 (9.6%) | 5 (23.8%) | 5 (35.7%) | 4 (66.7%) |
| Maternity leave | 7 (3.7%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Unemployed | 9 (4.8%) | 1 (1.9%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Sick leave | 2 (1.1%) | 3 (5.8%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Other | 1 (0.5%) | 1 (1.9%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Low socioeconomic status a | 12 (5.8%) | 7 (11.4%) | 3 (11.1%) | 2 (18.2%) | 2 (25.0%) |
| Height at first antenatal visit (cm) | 167.4 (5.9) n = 173 | 164.2 (6.2) n = 51 | 165.0 (5.1) n = 22 | 165.6 (5.1) n = 14 | 165.8 (2.2) n = 6 |
| Variable | n = 205 | n = 61 | n = 27 | n = 17 | n = 8 |
| Weight at first antenatal visit (kg) | 66.6 (10.8) n = 167 | 65.5 (11.3) n = 51 | 65.5 (11.3) n = 22 | 69.4 (11.1) n = 14 | 70.7 (11.5) n = 6 |
| BMI at first antenatal visit | 23.8 (3.9) n = 166 | 24.2 (4.1) n = 50 | 24.0 (3.9) n = 22 | 25.3 (4.1) n = 14 | 25.7 (4.4) n = 6 |
| Smoking or using snuff at first antenatal visit | 4 (1.9%) | 3 (5.3%) | 2 (8.0%) | 1 (6.3%) | 0 (0.0%) |
| Alcohol screening performance (AUDIT) b | |||||
| ≥6 points (risk behavior) | 8 (5.6%) | 3 (6.1%) | 1 (5.0%) | 1 (7.1%) | 0 (0.0%) |
| IVF in current pregnancy | 6 (3.0%) | 5 (8.6%) | 1 (4.0%) | 0 (0.0%) | 0 (0.0%) |
| Chronic hypertension at first antenatal visit | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Diabetes type 1 or 2 at first antenatal visit | 0 (0.0%) | 1 (1.8%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Renal disease at first antenatal visit | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Conization prior to inclusion date | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Parity | |||||
| Nullipara | 111 (56.9%) | 34 (55.7%) | 16 (59.3%) | 11 (40.7%) | 6 (75%) |
| Previous stillbirths ≥1 | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Previous late miscarriage | 3 (1.5%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) |
| Previous spontaneous PTD <37 weeks ≥1 | 3 (1.5%) | 6 (9.8%) | 1 (3.7%) | 0 (0.0%) | 0 (0.0%) |
Note: For categorical variables, n (%) is presented, and for continuous variables. mean (SD) is presented. Adapted from: Göransson et al. 47
Abbreviations: AUDIT, alcohol use disorder test; BMI, body mass index (kg/m2); IVF, in vitro fertilization; PTD, preterm delivery; sPTD, spontaneous preterm delivery; sPTD, spontaneous preterm delivery.
a
Low socioeconomic status defined as education ≤9 years, unemployment, and/or sick leave.
b
Alcohol screening by AUDIT (Alcohol Use Disorder Test) tool according to antenatal care routines. 47