Earlier induction of labour in post term pregnancies--A historical cohort study.
OBJECTIVE
to evaluate a change of guideline for earlier induction of labour in post term pregnancies and its possible impact on selected birth interventions and outcome of the newborn.


METHODS
a historical cohort study.


METHODS
Department of Obstetrics at Aarhus University Hospital in Denmark.


METHODS
18,247 women giving birth between 1 January 2009 and 12 December 2012.


METHODS
to compare induction of labour in two consecutive time periods before and after implementation of a new guideline on induction of labour (42 weeks versus 41 weeks plus five days gestational age) in post term pregnancy. t-Test and χ(2) were used to calculate means of gestational age and relative risk (RR) of selected birth and newborn outcomes. Stratification by Mantel-Haenszel-analysis was used to adjust for possible confounders. Robson׳s classification system 'Ten Group Classification System' was used to create comparable groups within the performed analysis.


RESULTS
a difference in means of three gestational days after implementation of the new guideline on earlier induction of labour was found together with an overall unadjusted decrease in emergency caesarean section rate of 30% (RR 0.70, 95% CI; 0.54-0.91). Stratified analysis on parity showed a reduction in emergency caesarean section but only in nulliparous women (RR 0.78, 95% CI; 0.66-0.92), whereas the analysis in multiparous women showed a non-statistically significant increased risk of emergency caesarean section (RR 1.39, 95% CI; 0.89-2.18). No differences were found in assisted vaginal childbirths and outcome in newborns concerning Apgar score, pH and standard base excess in women induced in 42 weeks versus 41 weeks plus five days gestational age.


CONCLUSIONS
the findings of this study suggest that earlier induction of labour due to post term pregnancy has a positive influence, but only in nulliparous women, by lowering the risk of emergency caesarean section evidently without increasing the risk on adverse outcome in newborns.
Department of Obstetrics and Gynaecology, Aarhus University Hospital, Aarhus, Denmark; Department of Public Health, Aarhus University, Aarhus, Denmark. Electronic address: kjeldsen_louise@hotmail.com.
Louise L
LL
Kjeldsen
Department of Public Health, Aarhus University, Aarhus, Denmark; Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark.
Mette
M
Sindberg
Department of Obstetrics and Gynaecology, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; Centre of Research in Rehabilitation (CORIR), Aarhus University Hospital, Aarhus, Denmark.
Rikke D
RD
Maimburg
D000328:Adult; D002585:Cesarean Section / Q000009:adverse effects; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D005865:Gestational Age; D017408:Guidelines as Topic / Q000592:standards*; D006801:Humans; D007231:Infant, Newborn; D007751:Labor, Induced / Q000009:adverse effects / Q000706:statistics & numerical data*; D011247:Pregnancy; D011273:Pregnancy, Prolonged / Q000188:drug therapy*
Caesarean section; Induced labour; Perinatal mortality; Prolonged pregnancy; Vacuum extraction