Fig. 2From: Temporal trends of preterm birth in Shenzhen, China: a retrospective studyContributions 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 indexBack to article page