Abstract:Objective To investigate the distribution of the number of cytosine-guanine-guanine (CGG) repeats located in fragile X mental retardation 1(FMR1) gene in women of child-bearing age with adverse pregnancy and childbirth history. Methods A total of 521 pregnant women admitted to Mianyang Central Hospital from August 2018 to November 2019 were randomly selected and divided into study group (with history of adverse pregnancy and childbirth,n=261) and control group(without history of adverse pregnancy and childbirth,n=260).After drawing venous blood (2 ml) and extracting DNA in each subject,CGG repeats in FMR1 gene were detected by fluorescence polymerase chain reaction (PCR) and capillary electrophoresis. Results There were 35 different CGG repeat number with variation range between 20-200 in 521 cases.The most common CGG repeat number was 31（32.63%,170 cases）,and the others respectively were 28 (27.83%,145 cases),35(14.97%,78 cases)，less than 28 (3.84%,20 cases),29,30,32,33,34 (14.97%,78 cases in total) and more than 35 (5.76%,30 cases).There were 4 cases of premutation and 3 cases of grey-zone in study group,while there were 0 case of premutation and 0 case of grey-zone in control group,with significant differences in them between two groups (P<0.05).In study group,CGG repeats number was more than 100 in 3 cases.In this research,all abnormalities of FMR1 gene presented with heterozygous mutations. Conclusion The risk of premutation carring of FMR1 gene is higher in women with adverse pregnancy and childbirth history,in whom the screening of FMR1 gene can provide better reproductive counseling for them from the perspective of gene expression.