Maternal age and the risk of fetal aneuploidy: A nationwide cohort study of more than 500 000 singleton pregnancies in Denmark from 2008 to 2017

IntroductionIn this register-based study of pregnancies in Denmark, we assessed the associations between maternal age and the risk of fetal aneuploidies (trisomy 21, trisomy 18, trisomy 13, triploidy, monosomy X and other sex chromosome aberrations). Additionally, we aimed to disentangle the maternal age-related effect on fetal aneuploidies by cases with translocation trisomies and mosaicisms.Material and methodsWe followed a nationwide cohort of 542 375 singleton-pregnant women attending first trimester screening in Denmark between 2008 and 2017 until delivery, miscarriage or termination of pregnancy. We used six maternal age categories and retrieved information on genetically confirmed aneuploidies of the fetus and infant from the national cytogenetic register.ResultsWe confirmed the known associations between advanced maternal age and higher risk of trisomy 21, 18, 13 and other sex chromosome aberrations, especially in women aged >= 35 years, whereas we found no age-related associations with triploidy or monosomy X. Cases with translocation trisomies and mosaicisms did not influence the overall reported association between maternal age and aneuploidies.ConclusionThis study provides insight into the accurate risk of fetal aneuploidies that pregnant women of advanced ages encounter. With this study, we found an association between advanced maternal age and the risk of trisomy 21, 18, 13 and other sex chromosome aberrations. In addition to this, we observed that cases with translocation trisomies and mosaicisms did not influence the overall reported association between maternal age and aneuploidies. In other words, we confirm the findings of previous studies, but we are one of the first to provide meaningful estimates on maternal age-related risk of more specific types of aneuploidies due to our large dataset and high level of power.image