Variables
PTB < 37 weeks n=187 (%)
p-value
PTB < 34 weeks n=91(%)
p-value
Demographic characteristics
Age 32.8±4.2 0.014 32.4±42 0.657
BMI before pregnancy
Normal(18.5-23.9 kg/m2) 87(27.6) 41(13.3)
overweight(24.0-27.9 kg/m2) 43(47.3) 0.000 19(22.4) 0.040
obesity(≥28.0 kg/m2) 20(50.0) 0.001 11(28.9) 0.018
Obstetric data
Pregnancy frequency
0 to 2 times 126(29.8) 63(15.3)
≥3 times 61(47.3) 0.000 28(22.6) 0.060
Pregnancy interval (year) 4.2±3.4 0.685 4.4±36 0.540
Multiparous
no 132(32.6) 62(15.7)
yes 55(36.7) 0.367 29(20.1) 0.228
Twin pregnancy
no 110(24.9) 57(13.3)
yes 77(67.5) 0.000 34(30.9) 0.000
Mode of fertilization
nature 116(26.4) 57(13.3)
IVF-ET 70(60.9) 0.000 34(31.2) 0.000
Gestational age of 1st short cervix (week) 26.2±5.5 0.000 24.9±5.9 0.000
CL of 1st short cervix (mm) 18.8±5.1 0.000 17.9±6.1 0.000
Amniotic fluid sludge
no 117(32.8) 83(15.9)
yes 10(66.7) 0.006 8(53.3) 0.001*
Gestational age of delivery (week) 32.3±4.3 29.3±4.5
Risky history
Induced abortion
0 132(32.8) 70(17.9)
≥1 time 55(36.2) 0.446 21(14.3) 0.319
Later-period spontaneous abortion
0 180(33.5) 86(16.5)
≥1 time 7(38.9) 0.635 5(29.4) 0.184*
Intrauterine operation frequency(except abortion)
0 153(32.5) 76(16.6)
≥1 time 34(40.5) 0.153 15(18.5) 0.676
History of forceps midwifery
no 187(33.9) 91(17.0)
yes 0(0) 0.554* 0 1.000*
History of cesarean delivery
no 36(33.1) 79(16.3)
yes 21(38.9) 0.395 12(23.1) 0.212
History of PTB
no 175(32.5) 84(16.1)
yes 12(70.6) 0.001 7(41.2) 0.014*
History of short cervix
no 181(33.3) 85(16.1)
yes 6(54.5) 0.195* 6(54.5) 0.005*
History of PPROM
no 183(33.5) 89(16.8)
yes 4(50.0) 0.452* 2(25.0) 0.539
History of LEEP
no 176(33.5) 86(16.9)
yes 11(37.9) 0.620 5(17.9) 0.800*
Preexisting comorbidities
Autoimmune disease
no 177(32.7) 86(16.4)
yes 10(71.4) 0.007* 5(35.7) 0.070*
PCOS
no 179(33.0) 86(16.3)
yes 8(61.5) 0.040* 5(41.7) 0.037*
hypothyroidism
no 172(34.1) 83(17.0)
yes 15(30.0) 0.562 8(16.3) 0.908
Pregestational diabetes mellitus
no 180(33.2) 88(16.8)
yes 7(53.8) 0.141* 3(23.1) 0.469*
Pregestational hypertension
no 178(33.5) 83(16.1)
yes 9(39.1) 0.573 8(36.4) 0.020*
Polyhydramnios#
no 178(33.3) 86(16.6)
yes 9(42.9) 0.365 5(23.8) 0.376*
Gestational diabetes mellitus#
no 123(34.9) 62(18.1)
yes 64(31.5) 0.412 29(14.9) 0.341
Blood pressure state#
normal 156(32.0) 79(16.7)
Gestational hypertension 4(18.2) 0.765* 1(4.8) 0.230*
Preeclampsia without serious manifestation 4(33.3) 1.000* 0 0.230*
Preeclampsia with serious manifestation 15(68.2) 0.000 7(33.3) 0.082*
Chronic hypertension complicating pregnancy 8(66.7) 0.047 4(33.3) 0.132*