Reproduction Abstracts

Low weight at birth may affect the onset of sexual maturation. Early puberty timing in those being small for gestational age might be explained by fetal reprogramming that helps to adapt for the poor-resource postnatal life and be ready earlier for reproduction. Biological plausibility for this association prompted for many epidemiological studies aimed to test a relationship between low birth weight and age at menarche (AAM) as a reliable indicator of puberty timing.

Materials and methods: Following the MOOSE guidelines for meta-analysis of observational studies, we found 27 relevant studies in the MEDLINE database. Among them, we identified seven studies with the data of good quality where birth weight was assigned as continuous variable and AAM was treated as categorical variable. The total sample included 1232 subjects with early and 2214 with late AAM. R statistical software was used for analysis. Due to the high heterogeneity of the data, the random-effects model was used.

Results and discussion: The meta-analysis under the random-effects model showed no significant association between birth weight and AAM (std diff=−0.503, P=0.409). Although this meta-analysis did not confirm the association between birth weight and AAM, but it helped to clarify problems with data and the design of studies that had been analysed. It seems that the real effect of low birth weight was underestimated due to misclassification of early and late AAM. We found that the data gave conflicting results due to the inappropriate study design, insufficient adjustments and lack of biological plausibility to establish causality.