Dental Caries According to Gestational Age and Birth Weight: Meta-Analysis Considering Selective Reporting Bias

Objectives: This is an ongoing systematic review of observational studies about occurence of dental caries in preterm and low birth weight (LBW) children compared to full-term and normal birth weight (NBW) children. We aimed to meta-analyze selective reporting bias in title, abstracts and keywordsand how it can input selection bias in the final effect estimate.
Methods: A search was conducted in eight electronic databases up to November 2018. Independent paired reviewers screened studies and extracted data. Dental caries was meta-analyzed comparing the exposures: LBW versus NBW children; preterm versus full-term children. We performed a subgroup analysis for studies that cited important uniterms (e.g. gestational age, preterm, birth weight) in title, abstract and keywords versus studies that did not. We calculated OR (odds ratio), 95%CI using random effect model when heterogeneity was <0.05.
Results: Studies showing positive effect between dental caries and birth weight or gestational age had more chance to cite the uniterms than studies with null effect between dental caries and the exposure (OR: 2.8 and 2.9, respectively). In subgroup analysis, studies that cited the uniterms showed that LBW (OR: 1.51; 1.17-1.93) and preterm children (OR: 1.49; 1.14-1.94) were more likely to have dental caries than their peers. However, the studies that did not cite the uniterms found similar chance of dental caries regardless of birth weight or gestational age (LBW versus NBW: OR: 1.03; 0.74-1.41; and preterm versus full-terms: OR: 0.85; 0.62-1.18).
Conclusions: There is selection of reporting bias in studies evaluating risk factors of dental caries that can change the final effect estimate. Studies with positive results were more likely to include related uniterms on title, abstract and keywords than studies with negative results. In order to avoid selection bias in systematic reviews of observational studies about dental caries, authors should search for other risk factors than the exposure of interest.
Prospero number: CRD42018118086