Rates of recurrent preterm birth by obstetrical history and cervical length

Rates of preterm birth less than 32 and less than 35 weeks were similar in women whose cervical length was less than 25 mm at 220 to 246 weeks, regardless of number of prior preterm births. Women with 2 prior preterm births and a cervix greater than 35 mm were at low risk for subsequent preterm birth less than 35 weeks.