Table 2 Regression analysis identifying factors associated with preterm birth in Hubei Province, China (2001 – 2012)

Year

1.01 (1.00 - 1.01)

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Maternal age (<35 y vs. ≥ 35 y)

5.28 (5.04 - 5.45)

0.57(0.55-0.58)

Gestational week(<34 week vs. ≥ 34 week)

2.21 (1.86 - 2.63)

----

Birth weight(<2.5 kg vs. ≥ 2.5 kg)

1.08 (1.05 -1.13)

----

Pregnancy parity(1 vs. ≥ 2)

2.80 (2.69 - 2.95)

----

Birth parity (1 vs. ≥ 2)

1.08 (1.01 - 1.10)

----

Assisted reproductive technology

(yes vs. no)

1.97 (1.91 -2.05)

3.67 (3.56-3.78)

Income (<500 USD/month vs. ≥ 500 USD/month)

1.27 (1.22- 1.32)

0.63 (0.61-0.66)

Education (>9 years vs. ≤ 9 years)

0.71 (0.49 - 0.91)

1.04 (1.01-1.06)

Residence (rural vs. urban)

1.37 (1.35 - 1.39)

1.27 (1.24-1.30)

Newborn Emergency Transport Service (yes vs. no)

3.13 (3.02 - 3.23)

----

Infant gender (female vs. male)

0.59 ( 0.56 - 0.63)

3.31 (3.23 -3.39)

Occupation (physical labor vs. office job)

2.16 (2.09 - 2.23)

----

Single birth

0.91 (0.89 - 0.97)

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