title: When to induce labor for post-term? A study of induction at 41 weeks versus 42 weeks.
abstract: OBJECTIVE
  To evaluate the pregnancy outcomes of two policies of timing of induction of labor for post-term pregnancies.
  
  
  METHODS
  It is a retrospective study in a University obstetric unit from 1997 to 2002. Five thousand eight hundred and ninety-two singleton, cephalic pregnancies with gestational age at delivery at or more than 41 completed weeks were studied. They were divided into two groups. Group A included women who delivered from January 1997 to February 1999 when the policy of the department was to induce labor for post-maturity at 42 weeks of gestation. Group B included those delivered between March 1999 and December 2002 when the timing of induction for post-term was advanced to 41 weeks. The intrapartum characteristics, delivery and perinatal outcomes were analyzed by Student's t-test and Chi-square test for continuous and categorical variables, respectively.
  
  
  RESULTS
  Two thousand one hundred and seventy-six women were studied in Group A and 3716 in Group B. Twenty-nine percent of these pregnancies in Group A required induction of labor whereas 20.3% were for post-term. In Group B, 58% of pregnancies had labor induction and 55% for post-maturity. For the pregnancies undergoing induction of labor for post-term, both the duration of labor (P<0.001) and the need of intrapartum epidural analgesia were increased (OR 1.3, 95% CI: 1.0-1.6) in Group B. However, there was no significant difference in the mode of delivery, apgar scores and stillbirths between the two study periods.
  
  
  CONCLUSIONS
  Compared to routine induction at 42 weeks, induction at 41 weeks is associated with a significantly higher risk of use of medical interventions and associated complications, with no observable benefits.
authors.affiliation: Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Princes of Wales Hospital, Shatin, Hong Kong. angelfok@cuhk.edu.hk
authors.forename: Wing Yee
authors.initials: WY
authors.lastname: Fok
authors.forename: Louis Yik-Si
authors.initials: LY
authors.lastname: Chan
authors.forename: Michelle Hang Yuet
authors.initials: MH
authors.lastname: Tsui
authors.forename: Tse Ngong
authors.initials: TN
authors.lastname: Leung
authors.forename: Tze Kin
authors.initials: TK
authors.lastname: Lau
authors.forename: Tony Kwok Hung
authors.initials: TK
authors.lastname: Chung
mesh_terms: D005260:Female; D005865:Gestational Age; D006723:Hong Kong; D006801:Humans; D007231:Infant, Newborn; D007233:Infant, Postmature; D007751:Labor, Induced / Q000379:methods / Q000706:statistics & numerical data; D011247:Pregnancy; D012189:Retrospective Studies; D016896:Treatment Outcome