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Table 3 Associations between parity/maternal age and adverse birth outcomes (adjusted RR and 95% CI)

From: Parity and the risks of adverse birth outcomes: a retrospective study among Chinese

Adverse birth outcomes Maternal age (y)
< 25 25–29 30–34 ≥35
PTB
 Nulliparity 0.94 (0.90, 0.97) 1.0 (ref) 1.20 (1.15, 1.25) 1.63 (1.51, 1.76)
 Multiparity 0.94 (0.88, 1.00) 0.96 (0.92, 0.99) 1.05 (1.01, 1.09) 1.39 (1.32, 1.45)
LBW
 Nulliparity 1.06 (1.02, 1.10) 1.0 (ref) 1.27 (1.21, 1.34) 1.56 (1.41, 1.73)
 Multiparity 0.86 (0.79, 0.93) 0.81 (0.78, 0.85) 0.84 (0.80, 0.88) 1.14 (1.07, 1.21)
SGA
 Nulliparity 1.14 (1.11, 1.17) 1.0 (ref) 1.04 (1.01, 1.08) 1.13 (1.04, 1.22)
 Multiparity 0.88 (0.84, 0.93) 0.68 (0.66, 0.70) 0.63 (0.61, 0.65) 0.73 (0.70, 0.77)
  1. PTB was defined as gestational age < 37 weeks, LBW was defined as birth weight < 2500 g; SGA was defined as birth weight below 10th centile for specific gestational age and sex
  2. Reference group: Nulliparity/aged between 25 and 29 years
  3. Adjusted for maternal race, area of residence, immigrant status, education, pre-pregnancy obesity, paternal age and race, and sex of newborn
  4. Abbreviations: PTB Preterm Birth, LBW Low Birth Weight, SGA Small for Gestational Age