The effects of induction of labor prior to post-term in low-risk pregnancies: a systematic review

Rationale

When a pregnancy is post-term, i.e. exceeding 14 days past estimated due date, it has long been obstetric practice to recommend induction of labor. In the context of a general trend towards earlier inductions, we wished to clarify whether this shift in clinical practice implies negative maternal or perinatal consequences. Hence, we examined effects of routine induction at 41+0-6 compared to 42+0-6 gestational weeks (GW) in low-risk pregnancies.

Method

We performed a systematic review and used validated tools for study selection and quality/evidence assessment (Joanna Briggs Institute; GRADE). We included 2 randomized and 2 quasi-experimental trials, and 3 cohort studies andcalculated relative risk ratios (RR), mean differences, and 95% confidence intervals (CI), on pooled data where relevant.

Results/Conclusions

Compared to expectant management, we found routine labor induction at 41+0-6 GW associated with the following outcomes (RR and CI in brackets): cesarean section (overall) (1.11 [1.09-1.14]), cesarean section (failure to progress) (1.43 [1.01-2.01]), chorioamnionitis (1.13 [1.05-1.21]), labor dystocia (1.29 [1.22-1.37]), precipitate labor (2.75 [1.45-5.20]), uterine rupture (1.97 [1.54-2.52]), pH < 7.10 (1.90 [1.48-2.43]), oligohydramnios (0.40 [0.24-0.67], and meconium stained amniotic fluid (0.82 [0.75-0.91]). Data did not allow for conclusions on perinatal death.

Implications

Our findings do not support routine labor induction prior to post-term (41+0-6 GW) in low-risk pregnancies, and desirable effects do not appear to outweigh undesirable effects. We recommend an increased awareness about inclusion criteria in systematic reviews when used for guideline development to ensure that the evidence base for clinical guidelines is based on studies that reflect contemporary practice.