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. Author manuscript; available in PMC: 2016 Mar 11.
Published in final edited form as: JAMA. 2015 Sep 8;314(10):1039–1051. doi: 10.1001/jama.2015.10244
Adjusted RR (95% CI) for the change per year 2009–2012
22 weeks 23 weeks 24 weeks 25 weeks
1.06 (0.89–1.25) 1.09 (1.05–1.14) 1.05 (1.03–1.07) 1.02 (1.01–1.03)
26 weeks 27 weeks 28 weeks
1.00 (0.996–1.015) 1.01 (1.002–1.016) 1.00 (0.998–1.011)