Abstract
BACKGROUND: Advanced maternal age decreased success of pregnancy rate in the assisted reproductive technology (ART) treatment. We aimed to investigate the association between age and miscarriages in women who required ART for conception. METHODS: A cohort study was conducted using a 10-year sample of 14,898 pregnancy cycles with ART treatment in Xi'an, China. The effects of women's age on miscarriage were assessed using Poisson regression models. The threshold effect between age and miscarriage was explored through curve fitting. RESULTS: Compared with lower than 30 years, the risks of early miscarriage and miscarriage were higher in the older age groups (early miscarriage: [35-37 years: RR=1.48, 95% confidence interval (CI): 1.26 to 1.74; ≥38 years: RR=2.25, 95% CI: 1.87 to 2.72]; miscarriage: [35-37 years: RR=1.45, 95%CI: 1.24 to 1.69; ≥38 years: RR=2.17, 95%CI: 1.82 to 2.60]). The nonlinear relationship between age and early miscarriage and miscarriages were observed. The risk of early miscarriage and miscarriage rapidly increased with age after the turning point (age=33 years) (<33 years: [early miscarriage: RR=1.02, 95% CI: 1.00 to 1.04; miscarriage: RR=1.02, 95% CI: 1.00 to 1.03]; ≥33 years: [early miscarriage: RR=1.11, 95% CI: 1.08 to 1.13; miscarriage: RR=1.10, 95% CI: 1.07 to 1.13]). CONCLUSION: Among pregnancy cycles undergoing ART, advanced age is associated with higher risk of early miscarriage and miscarriage, and nonlinear relationship between age and early miscarriage and miscarriage were found. More attention should be paid to the risk of pregnant women with older than 33 years in ART treatment.