The diagnosis and natural history of false preterm labor

To estimate the natural history of pregnancies in women who present with preterm labor symptoms and who are sent home with a diagnosis of false labor.

A prospective observational study of women with singletons and intact membranes who presented to triage between 24 0/7 and 33 6/7 weeks of gestation with preterm labor symptoms and cervical dilation less than 2 cm was conducted. Women sent home with a diagnosis of false preterm labor were analyzed against a comparable general obstetric population delivered during the same time period. The primary outcome was delivery before 37 weeks of gestation. Secondary outcomes included the interval between presentation and delivery, as well as maternal and neonatal outcomes.

Of the 843 women who met inclusion criteria, 690 (82%) were sent home with a diagnosis of false preterm labor and 153 (18%) were admitted to labor and delivery. When analyzed compared with a comparable general obstetric population, women sent home had a similar rate of birth before 34 weeks of gestation (2% compared with 1%, P=.28) but a higher rate of birth between 34 and 36 weeks of gestation (5% compared with 2%, P<.001). There was no difference in neonatal mortality (0% compared with 0.3%, P=.18). Women with cervical dilation of 1 cm at discharge were more likely to deliver before 34 weeks of gestation compared with nondilated women (5% compared with 1%, P=.02); however, 89% of the 1-cm group delivered more than 21 days after presentation.

Women sent home with a diagnosis of false preterm labor are not at increased risk for early preterm birth or neonatal mortality; however, they are at increased risk for late preterm birth.

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