Table 3 Characteristics and crude relative risk of factors associated with non-malformed singleton stillbirth.
Risk factors | Total births | Stillbirths | Crude relative risk (95% CI) | P-value |
|---|---|---|---|---|
No. (%) | No. (Rate per 1000 births) | |||
Total | 270,450 | 1,075 | ||
Maternal age, years | ||||
Mean | 32.2 ± 5.4 | 32.3 ± 5.6 | ||
<20 | 3,695 (1.4) | 17 (4.6) | 1.19 (0.74–1.93) | 0.5 |
20–34 | 169,382 (62.6) | 653 (3.9) | 1.00 | NA |
≥35 | 97,373 (36.0) | 405 (4.2) | 1.08 (0.95–1.22) | 0.2 |
Parity | ||||
0 | 140,686 (52.0) | 601 (4.3) | 1.17 (1.04–1.32) | 0.01 |
≥1 | 129,764 (48.0) | 474 (3.7) | 1.00 | NA |
Pre-pregnancy BMI, kg/m2 | ||||
Mean | 21.3 ± 3.6 | 21.7 ± 4.0 | ||
<18.5 | 47,091 (17.4) | 171 (3.6) | 0.95 (0.80–1.12) | 0.6 |
18.5–22.9 | 164,004 (60.6) | 627 (3.8) | 1.00 | NA |
23.0–29.9 | 50,316 (18.6) | 228 (4.5) | 1.19 (1.02–1.38) | 0.03 |
≥30.0 | 9,039 (3.3) | 49 (5.4) | 1.42 (1.06–1.90) | 0.02 |
Smoking | ||||
No | 261,163 (96.6) | 1,016 (3.9) | 1.00 | NA |
Yes | 9,287 (3.4) | 59 (6.4) | 1.63 (1.26–2.12) | <0.001 |
Use of ART | ||||
No | 251,782 (93.1) | 994 (3.9) | 1.00 | NA |
Yes | 18,668 (6.9) | 81 (4.3) | 1.10 (0.88–1.38) | 0.4 |
Pre-existing hypertension | ||||
No | 268,072 (99.1) | 1,040 (3.9) | 1.00 | NA |
Yes | 2,378 (0.9) | 35 (14.7) | 3.79 (2.71–5.31) | <0.001 |
Pre-existing diabetes mellitus | ||||
No | 268,357 (99.2) | 1,064 (4.0) | 1.00 | NA |
Yes | 2,093 (0.8) | 11 (5.3) | 1.33 (0.73–2.40) | 0.4 |
Thyroid disease | ||||
No | 262,029 (96.9) | 1,046 (4.0) | 1.00 | NA |
Yes | 8,421 (3.1) | 29 (3.4) | 0.86 (0.60–1.25) | 0.4 |
History of stillbirtha | ||||
No | 127,372 (98.2) | 456 (3.6) | 1.00 | NA |
Yes | 2,392 (1.8) | 18 (7.5) | 2.10 (1.31–3.37) | 0.002 |
History of preterm birtha | ||||
No | 122,382 (94.3) | 435 (3.6) | 1.00 | NA |
Yes | 7,382 (5.7) | 39 (5.3) | 1.49 (1.07–2.06) | 0.02 |
History of cesarean sectiona | ||||
No | 103,408 (79.7) | 389 (3.8) | 1.00 | NA |
Yes | 26,356 (20.3) | 85 (3.2) | 0.86 (0.68–1.08) | 0.2 |
PIH | ||||
No | 255,677 (94.5) | 978 (3.8) | 1.00 | NA |
Yes | 14,773 (5.5) | 97 (6.6) | 1.72 (1.39–2.11) | <0.001 |
Amniotic fluid volume | ||||
Oligohydramnios | 4,858 (1.8) | 68 (14.0) | 3.73 (2.92–4.77) | <0.001 |
Normal | 264,291 (97.7) | 991 (3.7) | 1.00 | NA |
Polyhydramnios | 1,301 (0.5) | 16 (12.3) | 3.28 (2.00–5.37) | <0.001 |
Infant sex | ||||
Male | 139,116 (51.4) | 546 (3.9) | 1.00 | NA |
Female | 131,334 (48.6) | 529 (4.0) | 1.03 (0.91–1.16) | 0.7 |
Infant size | ||||
SGA | 26,991 (10.0) | 486 (18.0) | 7.25 (6.41–8.20) | <0.001 |
AGA | 215,364 (79.6) | 535 (2.5) | 1.00 | NA |
LGA | 28,095 (10.4) | 54 (1.9) | 0.77 (0.58–1.02) | 0.07 |
Facility type | ||||
Comprehensive perinatal center | 90,190 (33.4) | 502 (5.6) | 1.00 | NA |
Regional perinatal center | 125,320 (46.3) | 448 (3.6) | 0.64 (0.57–0.73) | <0.001 |
General maternity unit | 54,9401 (20.3) | 125 (2.3) | 0.41 (0.34–0.50) | <0.001 |
