“…The population recruitment periods were 1 year in 12 studies [28,34,35 [5, 28, 29, 31-35, 38-42, 44, 49-51, 53, 55, 56, 58, 61, 66, 68-72, 75, 77, 79, 81, 82, 85-89] and seven studies used women's self-reported data [37,64,67,73,74,80]. However, regarding the methods of collecting prepregnancy BMI data: only two studies measured it [52,60], twelve used medical records [5,28,29,39,44,49,57,68,77,79,86,89], two used both medical records and self-reported data [43,76], and twenty four used self-reported prepregnancy BMI [29, 32, 34, 37, 45-48, 50, 51, 53, 54, 59, 62-67, 73, 75, 84, 85, 87].…”