Figure 1.

Preterm birth rates per 100 live births among singletons and twins by subtype of preterm birth, namely, spontaneous preterm birth, iatrogenic preterm birth and preterm birth following premature rupture of membranes for over 12 hours (PROM), United States, 1995 to 2005.

Lisonkova et al. BMC Pregnancy and Childbirth 2011 11:39   doi:10.1186/1471-2393-11-39
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