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. 2018 Mar 13;15:47. doi: 10.1186/s12978-018-0477-8

Fig. 2.

Fig. 2

Contributions of changing risk factors to changes in preterm birth incidence rate in Shenzhen, China, 2003-2012. PROM-PTB, preterm birth following premature rupture of membranes; MI-PTB, medically induced preterm birth; S-PTB, preterm birth due to spontaneous preterm labor; APNCU, the adequacy of prenatal care utilization index