Table 1.
Population characteristics of the discovery and the replication samples from the BBC.
| Discovery |
Replication |
||||
|---|---|---|---|---|---|
| Variablesa | TBs | Early sPTBs | TBs | sPTBsb | mPTBs |
| n | 144 | 146 | 54 | 41 | 14 |
| Maternal age, years | |||||
| <25 | 53 (36.8) | 58 (39.8) | 21 (38.9) | 15 (36.6) | 5 (35.7) |
| 25–34.9 | 70 (48.6) | 64 (43.8) | 25 (46.3) | 18 (43.9) | 6 (42.9) |
| ≥35 | 21 (14.6) | 24 (16.4) | 8 (14.8) | 8 (19.5) | 3 (21.4) |
| Pre-pregnancy BMI, kg/m2 | |||||
| <18.5 | 7 (4.9) | 5 (3.4) | 1 (1.9) | 1 (2.4) | 0 |
| 18.5–24.9 | 64 (44.4) | 60 (41.1) | 18 (33.3) | 18 (43.9) | 5 (35.7) |
| 25–29.9 | 35 (24.3) | 46 (31.5) | 20 (37.0) | 10 (24.4) | 5 (35.7) |
| ≥30 | 33 (22.9) | 28 (19.2) | 13 (24.1) | 9 (22.0) | 4 (28.6) |
| Unknown | 5 (3.5) | 7 (4.8) | 2 (3.7) | 3 (7.3) | 0 |
| Maternal smoking during pregnancy | |||||
| Never | 105(72.9) | 94 (64.4) | 45 (83.3) | 30 (73.2) | 10 (71.4) |
| Quitter | 12 (8.3) | 14 (9.6) | 5 (9.3) | 2 (4.8) | 2 (14.3) |
| Continuous | 22 (15.3) | 31 (21.2) | 3 (5.5) | 9 (22.0) | 2 (14.3) |
| Unknown | 5 (3.5) | 7 (4.8) | 1 (1.9) | 0 | 0 |
| Alcohol drinking, yes | 8 (5.6) | 11 (7.5) | 4 (7.4) | 5 (12.2) | 0 |
| Stress during pregnancy | |||||
| Mild | 57 (39.6) | 38 (26.0) | 15 (27.8) | 13 (31.7) | 5 (35.7) |
| Moderate | 51 (35.4) | 63 (43.2) | 30 (55.5) | 21 (51.2) | 5 (35.7) |
| High | 28 (19.4) | 34 (23.3) | 8 (14.8) | 7 (17.1) | 3 (21.4) |
| Unknown | 8 (5.6) | 11 (7.5) | 1 (1.9) | 0 | 1 (7.1) |
| Parity | |||||
| 0 | 55 (38.2) | 60 (41.1) | 22 (40.7) | 16 (39.0) | 6 (42.9) |
| 1 | 43 (29.9) | 42 (28.8) | 15 (27.8) | 12 (29.3) | 5 (35.7) |
| 2+ | 46 (31.9) | 44 (30.1) | 17 (31.5) | 13 (31.7) | 3 (21.4) |
| Illicit drug use | 34 (23.6) | 42 (28.8) | 7 (13.0) | 10 (24.4) | 5 (35.7) |
| Intrauterine inflammation | 25 (17.4) | 87 (59.6)*** | 5 (9.3) | 10 (24.4) | 0 (0)* |
| Diabetes/gestational diabetes | 4 (2.8) | 16 (10.9)* | 5 (9.3) | 8 (19.5) | 6 (42.9)** |
| Hypertensive disorder | 0 (0) | 17(11.6)*** | 5 (9.3) | 8 (19.5) | 12 (85.7)*** |
| Caesarian section | 34 (23.6) | 59 (40.4)** | 11 (20.4) | 12 (29.3) | 12 (85.7)*** |
| Baby's gender | |||||
| Boys | 68 (47.2) | 81 (55.5) | 28 (51.9) | 22 (53.7) | 6 (42.9) |
BMI: body mass index; PTB: preterm birth; mPTB: medically-indicated PTB; sPTB: spontaneous PTB; TB: term birth.
a
n(%) are shown in the Table.
b
including 7 mother-newborn pairs with early sPTBs and 34 pairs with late sPTBs.
#,*,**,***Each variable was compared between mothers with PTBs and mothers with TBs in the discovery stage and in the replication stage, respectively, using chi-square tests (or Fisher's exact tests) as appropriate. *P < 0.05; ** P < 0.01; *** P < 0.001