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. Author manuscript; available in PMC: 2015 Feb 1.
Published in final edited form as: Am J Obstet Gynecol. 2013 Sep 11;210(2):131.e1–131.e8. doi: 10.1016/j.ajog.2013.09.014

Table 3.

Risk of preterm birth < 37 weeks of gestation in third delivery by term versus preterm birth in first and second deliveries (n=10,819).a

Total
n (%)		 N (%) preterm in
3rd birth		 Unadjusted RR Adjusted RRb
Term birth in 1st delivery/Term birth in 2nd delivery 9441 (87.3) 468 (5.0) Referent Referent
Preterm birth in 1st delivery/ Term birth in 2nd delivery 580 (5.4) 101 (17.4) 3.51 [2.88, 4.28] 3.50 [2.86, 4.28]
Term birth in 1st delivery/Preterm birth in 2nd delivery 555 (5.1) 155 (27.9) 5.63 [4.80, 6.61] 5.50 [4.66, 6.50]
Preterm birth in 1st delivery/Preterm birth in 2nd delivery 243 (2.2) 142 (58.4) 11.79 [10.27, 13.53] 10.57 [9.05, 12.34]
a

Figures in parentheses are 95% confidence intervals except where noted

b

Models were adjusted for maternal age, race/ethnicity, pre-pregnancy body mass index, insurance, smoker, alcohol, illicit drug use, chronic medical disease.