Strengths and limitations
Our meta-analysis had several strengths. This study included primarily high quality RCTs providing the highest protection against bias, used the GRADE approach to assess the overall certainty of evidence. The study also had several limitations. Firstly, we restricted the inclusion of studies in English and Chinese, which could have led to missing of some relevant trials. Secondly, we observed statistically significant heterogeneity across studies. Such heterogeneity might preclude pooling of some intervention effects, so caution should be exercised when interpreting the results. Thirdly, due to insufficient data, we were unable to conduct subgroup analysis for birthweight and ethnicities. Fourthly, because of insufficient RCT for peanut oil and liquid petroleum jelly, so the interpretation of results should be cautious.