Prediction of Preterm Birth by Maternal Characteristics and Medical History in the Brazilian Population
Table 1
Baseline characteristics, obstetric history, and average risks for preterm birth before 34 weeks of the study population (Hospital das Clínicas, Ribeirão Pretro, São Paulo, Brazil, 2016).
Maternal characteristic
Term ()
Preterm 34–37 w ()
value§
Preterm <34 w ()
value§
TOTAL ()
Age (years), mean ± SD
25.6 ± 6.0
26.3 ± 6.1
0.31
27.1 ± 5.8
0.21
25.7 ± 6.0
Height (cm), mean ± SD
161.0 ± 6.3
160.1 ± 6.1
0.23
160.7 ± 6.3
0.84
160.9 ± 6.3
Ethnicity
Caucasian, n (%)
628 (51.8)
45 (51.7)
0.61
11 (47.8)
0.89
684 (51.7)
Afro-Brazilian, n (%)
139 (11.5)
8 (9.2)
2 (8.7)
149 (11.3)
Mixed, n (%)
442 (36.4)
33 (37.9)
10 (43.5)
485 (36.7)
Asian, n (%)
4 (0.3)
1 (1.1)
0 (0)
5 (0.4)
Smoking
146 (12.0)
15 (17.2)
0.16
9 (39.1)
0.001∗
170 (12.8)
Nonsmoking
1067 (88.0)
72 (82.8)
14 (60.9)
1153 (87.2)
Use of ovulation-inducing drug
16 (1.3)
16 (1.3)
0.62
0 (0)
1.00
16 (1.2)
Obstetric history
Primigravidae, n (%)
541 (44.6)
35 (40.2)
0.43
8 (34.8)
0.35
584 (44.1)
Previous miscarriage(s) <16 w n (%)
80 (6.6)
4 (4.6)
0.46
3 (13.0)
0.20
87 (6.6)
Previous sPTB 16–30 w (one event), n (%)
2 (0.2)
2 (2.3)
0.02∗
1 (4.3)
0.06
5 (0.4)
Previous sPTB 16–30 w (two events), n (%)
0 (0)
0 (0)
—
2 (8.7)
<0.001∗
2 (0.2)
Previous sPTB 16–30 w (one event) plus sPTB 31–36 w, n (%)
0 (0)
0 (0)
—
0 (0)
—
0 (0)
Previous sPTB 16–30 w (one event) plus term delivery, n (%)
1 (0.1)
0 (0)
1.00
0 (0)
0.98
1 (0.1)
Previous sPTB 16–30 w (two events) plus term delivery, n (%)
0 (0)
0 (0)
—
0 (0)
—
0 (0)
Previous sPTB 31–36 w, n (%)
26 (2.1)
5 (5.7)
0.05
1 (4.3)
0.40
32 (2.4)
Previous sPTB 31–36 w plus term delivery, n (%)
13 (1.1)
1 (1.1)
1.00
0 (0)
1.00
14 (1.1)
Previous iatrogenic delivery <37 w n (%)
8 (0.7)
1 (1.1)
0.47
1 (4.3)
0.16
10 (0.8)
Previous term deliveries, n (%)
543 (44.8)
39 (44.8)
0.99
7 (30.4)
0.17
589 (44.5)
Risk of preterm birth <34 w (%), mean ± SD
0.76 ± 0.50
0.99 ± 1.16
0.39
1.37 ± 1.59
<0.01∗
0.78 ± 0.6
§ value for each group when compared to term delivery; ∗Statistically significant at 0.05 significance level. SD: standard deviation; w: weeks of gestation; sPTB: spontaneous preterm birth. χ2 test and Fisher’s exact test for categorical variables and by Mann–Whitney U test for continuous variables.
