title: The accuracy of using last menstrual period to determine gestational age for first trimester medication abortion: a systematic review.
abstract: OBJECTIVE
  We sought to evaluate the accuracy of assessing gestational age (GA) prior to first trimester medication abortion using last menstrual period (LMP) compared to ultrasound (U/S).
  
  
  METHODS
  We searched Medline, Embase and Cochrane databases through October 2013 for peer-reviewed articles comparing LMP to U/S for GA dating in abortion care. Two teams of investigators independently evaluated data using standard abstraction forms. The US Preventive Services Task Force and Quality Assessment of Diagnostic Accuracy Studies guidelines were used to assess quality.
  
  
  RESULTS
  Of 318 articles identified, 5 met inclusion criteria. Three studies reported that 2.5-11.8% of women were eligible for medication abortion by LMP and ineligible by U/S. The number of women who underestimated GA using LMP compared to U/S ranged from 1.8 to 14.8%, with lower rates found when the sample was limited to a GA <63 days. Most women (90.5-99.1%) knew their LMP, 70.8-90.5% with certainty.
  
  
  CONCLUSIONS
  Our results support that LMP can be used to assess GA prior to medication abortion at GA <63 days. Further research looking at patient outcomes and identifying women eligible for medication abortion by LMP but ineligible by U/S is needed to confirm the safety and effectiveness of providing medication abortion using LMP alone to determine GA.
authors.affiliation: Montefiore Medical Center/Albert Einstein College of Medicine, Bronx NY. Electronic address: dschonbe@montefiore.org.
authors.forename: Dana
authors.initials: D
authors.lastname: Schonberg
authors.affiliation: Montefiore Medical Center/Albert Einstein College of Medicine, Bronx NY.
authors.forename: Lin-Fan
authors.initials: LF
authors.lastname: Wang
authors.affiliation: Albert Einstein College of Medicine, Bronx NY.
authors.forename: Ariana H
authors.initials: AH
authors.lastname: Bennett
authors.affiliation: Montefiore Medical Center/Albert Einstein College of Medicine, Bronx NY.
authors.forename: Marji
authors.initials: M
authors.lastname: Gold
authors.affiliation: Planned Parenthood of Orange and San Bernardino Counties, Orange, CA.
authors.forename: Emily
authors.initials: E
authors.lastname: Jackson
mesh_terms: D000028:Abortion, Induced; D005260:Female; D005865:Gestational Age; D006801:Humans; D008597:Menstrual Cycle; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D016216:Ultrasonography, Prenatal
keywords: Gestational age; Medication abortion; Menstruation; Pregnancy dating