Table 1 Comparison of sociodemographic characteristics of migrants and local women giving birth to live singletons between 2014 and 2020 in PRD Region

Maternal age, y (n, %)

16 ∽ 24

1,074,234 (20.58)

88,041 (12.76)

577,940 (20.69)

408,253 (23.52)

< 0.001 ^{A, B, C}

25 ∽ 29

1,970,479 (37.75)

256,200 (37.13)

1,092,518 (39.12)

621,761 (35.81)

30 ∽ 34

1,447,580 (27.74)

224,487(32.53)

739,376(26.47)

483,717(27.86)

35 ∽ 39

593,765 (11.38)

97,621(14.15)

315,716(11.30)

180,428(10.39)

40 ∽ 50

127,682 (2.45)

23,421 (3.39)

65,683 (2.35)

38,578 (2.22)

< 16 or missing data

5393 (0.10)

323 (0.05)

1744 (0.06)

3326 (0.19)

Infant sex (n, %)

male

2,792,678 (53.51)

368,491 (53.39)

1,495,098 (53.53)

929,089 (53.52)

< 0.001 ^{A, B, C}

female

2,425,934 (46.48)

321,567 (46.60)

1,297,607 (46.46)

806,760 (46.47)

Unknown

521 (0.01)

35 (0.01)

272 (0.01)

214 (0.01)

Delivery mode (n, %)

Vaginal delivery

3,535,799 (67.75)

447,506 (64.85)

1,947,974 (69.75)

1,140,319 (65.68)

< 0.001 ^{A, B, C}

Cesarean

1,683,334 (32.25)

242,587 (35.15)

845,003 (30.25)

595,744 (34.32)

Birth Season (n, %)

Spring

1,175,442 (22.52)

163,745 (23.73)

630,546 (22.58)

381,151 (21.96)

< 0.001 ^{A, B, C}

Summer

1,364,830 (26.15)

173,388 (25.13)

715,175 (25.61)

476,267 (27.43)

Autumn

1,496,777 (28.68)

183,662 (26.61)

804,837 (28.81)

508,278 (29.28)

Winter

1,182,084(22.65)

169,298 (24.53)

642,419 (23.00)

370,367 (21.33)

Mean gestational age mean ± SD (wk)

38.74 ± 1.50

38.59 ± 1.50

38.73 ± 1.49

38.81 ± 1.51

< 0.001 ^{A, B, C}

Mean birth weight mean ± SD (g)

3180.01 ± 440.70

3160.02 ± 439.31

3151.45 ± 432.63

3233.89 ± 449.08

< 0.001 ^{A, B, C}