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PURPOSE: Infants who remain in-utero after their due date are exposed to increasing risk of infection, late stillbirth and delivery complications. Much of the current literature on post-term outcomes is based on short term observations and the impacts may be substantially greater in the long term. The aim of this work is to perform a systematic review and meta-analysis to quantify the cognitive or educational impacts of post term delivery.
METHODS: Systematic review was performed by the two authors using Medline database (1960-2017). A title search was performed to identify likely relevant literature. Exposure terms were clarified to identify papers where the exposure was related to delivery after the infants' due date. Primary outcome was cognitive score. A quality assessment and data extraction pro forma was completed by both reviewers for all studies deemed to satisfy the inclusion and exclusion criteria. Meta-analysis used adjusted results where available. Small-study bias was assessed visually using a funnel plot and then formally tested using Egger's regression asymmetry test.
RESULTS: Medline was searched on the 4 July 2018; and produced a list of 1318 publications. Of these, 43 abstracts were screened, and of these a total of 10 full-text papers were reviewed. A further three papers were identified during this review and contributed to a total of 13 papers. The publications dated from 1969 to 2017. Two studies presented a binary outcome for cognitive measures and combined estimates found that the risk of a low cognitive score was higher in post-term infants compared to term infants (odds ratio [OR] 1.06 [1.04-1.08]). Four papers presented the association with mean cognitive measures and post-term delivery, and all demonstrated a mean reduction in scores in the post-term group. A combined estimate showed strong evidence of a reduction in cognitive scores across the four studies (-1.90 [-3.50 to -0.31]). There was little evidence of heterogeneity in the studies which reported cognitive outcomes (other p-values >.2).
CONCLUSION: This meta-analysis has found that post term birth (>41 + 6 weeks) is associated with small but significant negative effects on cognitive outcomes when compared with delivery at, or around term. The effect, while small, is compounded by a common exposure and appears consistent in the studies identified. Less evidence was found for a measurable impact on early developmental measures or educational outcomes. This may further help inform the debate on the timing of otherwise uncomplicated pregnancies and further trials in this area.