Abstract: Objective To investigate the association of maternal age and adverse neonatal outcomes in singleton pregnancies.Methods A retrospective cohort study was conducted to obtain the sociodemographic data, maternal history and pregnancy status of pregnant women in our hospital Obstetrics and Gyncology Hospital of Fudan University from January 2006 to December 2018 by reviewing obstetric and neonatal information. According to maternal age, the pregnant women were divided into three groups of low age group(<20 years old), appropriate age group (20-34 years old) and advanced age group (35 years of age or older). We analyzed the baseline maternal characteristics in all maternal age groups, prevalence of pregnancy outcomes in relation to the maternal age groups and the incidence of adverse neonatal outcomes. We analyzed the comparisons between groups using χ² or Fisher exact test. The association between each maternal age group and each adverse outcome was analyzed by a multivariate logistic regression model. At the same time, a subgroup analysis of maternal age was performed. The mothers aged 20-34 years as the reference group and the odds ratio (crude OR) and adjusted odds ratio (adjusted OR) and 95% confidence intervals (95%CI) were used to indicate the risk of neonatal adverse outcomes associated with subgroups.Results In recent years, the proportion of advanced maternal age in total pregnancy women has increased. From 2006 to 2014, the proportion of advanced age group in total pregnancy women 6.9%-9.9%, and the proportion of advanced age group in 2015, 2016, 2017 and 2018 was 13.1%, 13.8%, 17.6% and 19.6%, respectively. There were significant differences in the proportion of floating population, parturients and cesarean section between the low age group and the appropriate age group, the advanced age group and the appropriate age group as well (P all < 0.001). The non-cephalic birth type, abverse pregnancy history and the proportion of male newborns in advanced age group were higher than those in the appropriate age group (P < 0.05). After adjusting a variety of factors, the incidence of premature infants in low age group and advanced age group was 1.88 times (95%CI:1.34-2.65) and 1.31 times (95%CI:1.21-1.42) higher than that in the appropriate age group, respectively. The incidence of mid-term premature infants in the low age group and the advanced age group was 2.83 times (95%CI:1.45-5.54) and 1.34 times (95%CI:1.13-1.60) higher than that in the appropriate age group, respectively. The incidence of late premature infants in the low age group and the advanced age group was 1.75 times (95%CI:1.22-2.51) and 1.27 times (95%CI:1.17-1.36) higher than that in the appropriate age group, respectively. The incidence of low birth weight infants in the low age group and the advanced age group was 2.35 times (95%CI:1.66-3.33) and 1.26 times (95%CI:1.16-1.37) higher than that in the appropriate age group, respectively. The incidence of birth defects in the advanced age group was 1.39 times higher than that in the appropriate age group (95%CI:1.20-1.62).Conclusion The risk of preterm, moderate preterm, late preterm infants, low birth weight in both the low age group and the advanced age group were significantly higher than women aged 20-34 years, respectively. The management of floating population should be strengthened and prenatal examination should be carried out regularly. For the advanced age group, we should prevent the occurrence of birth defects, actively deal with complications during pregnancy, strengthen monitoring in the middle and late pregnancy, and prevent perinatal infection. The results of this study can contribute to the prenatal counseling and management of pregnant women of different gestational ages.

Key words: Adverse outcomes, Gestational ages, Mother, Newborns