Risk of preterm birth in a third pregnancy

Obstetric history	Risk of PTB in third pregnancy (%)
Two prior preterm births	42
Both at 32 to 36 weeks	33
Both at less than 32 weeks	57
Term birth followed by PTB	21
PTB followed by term birth	13
Two prior term births	5

These data were derived from individuals with spontaneous or indicated preterm birth. Preterm birth is defined as birth prior to 37 weeks gestation.

PTB: preterm birth.

Data from: McManemy J, Cooke E, Amon E, Leet T. Recurrence risk for preterm delivery. Am J Obstet Gynecol 2007; 196:576.

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