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Table 2 Incidences of pregnancy complications by parity and maternal age groups

From: Pregnancy complications among nulliparous and multiparous women with advanced maternal age: a community-based prospective cohort study in China

Variables Overall Nulliparas Multiparas
20–29ya 30–34y ≥35y p 20–29y 30–34y ≥35y p
(n) (10,171) (4851) (344) (65)   (3010) (1293) (507)  
Gestational hypertension (n, %) 430 (4.2) 126 (2.6) 34 (9.9) 12 (18.5) < 0.001 125 (4.2) 109 (8.4) 20 (3.9) < 0.001
Preeclampsia/eclampsia (n, %) 352 (3.5) 106 (2.2) 167 (4.9) 12 (18.5) < 0.001 114 (3.8) 87 (6.7) 16 (3.2) < 0.001
Gestational diabetes mellitus (GDM, n, %) 145 (1.4) 63 (1.3) 10 (2.9) 1 (1.5) 0.092 31 (1.0) 23 (1.8) 17 (3.4) < 0.001
Anemia (n, %) 380 (3.7) 151 (3.1) 6 (1.7) 6 (9.2) 0.006 119 (4.0) 59 (4.6) 37 (7.3) 0.004
Polyhydramnios (n, %) 89 (0.9) 32 (0.7) 4 (1.2) 3 (4.6) 0.001 21 (0.7) 17 (1.3) 12 (2.4) 0.001
Oligohydramnios (n, %) 101 (1.0) 25 (0.5) 13 (3.8) 1 (1.5) < 0.001 36 (1.2) 17 (1.3) 8 (1.6) 0.462
Placenta previa (n, %) 146 (1.4) 33 (0.7) 10 (2.9) 0 (0.0) < 0.001 52 (1.7) 37 (2.9) 14 (2.8) 0.086
Premature rupture of membrane (n, %) 90 (0.9) 43 (0.9) 7 (2.0) 4 (6.2) < 0.001 11 (0.4) 14 (1.1) 10 (2.0) < 0.001
Infectious disease (n, %) 158 (1.6) 29 (0.6) 3 (0.9) 0 (0.0) < 0.001 75 (2.5) 36 (2.8) 14 (2.8) < 0.001
Threatened abortion (n, %) 192 (1.9) 59 (1.2) 0 (0.0) 0 (0.0) 0.154 76 (2.5) 48 (3.7) 9 (1.8) < 0.001
Preterm labor (n, %) 950 (9.4) 450 (9.3) 38 (11.1) 9 (13.8) 0.37 241 (8.1) 130 (10.1) 73 (14.5) < 0.001
Low birth weight (n, %) 289 (2.8) 37 (0.8) 1 (0.3) 1 (1.5) 0.004 178 (5.9) 45 (3.5) 25 (4.9) 0.002
Mode of delivery (n, %)      < 0.001     < 0.001
 Vaginal birth 6371 (64.5) 3401 (72.0) 189 (56.9) 94 (62.3)   1852 (63.1) 592 (47.4) 243 (49.6)  
 Caesarean 3506 (35.5) 1321 (28.0) 143 (43.1) 40 (63.5)   1081 (36.9) 657 (52.6) 247 (51.1)  
  1. aWomen aged 20–24 years and 25–29 years were combined as one age group considering the low incidence of pregnancy complications in the two groups