Pregnancy outcomes in Chinese urban women at a very advanced maternal age

In the past three decades, delaying child bearing to a later reproductive age has become increasingly common, especially in some high-income developed countries [1, 2]. In some parts of the world, the percentage of women commencing childbearing at 35 years and beyond is stable at about 20% [3-5]. Well-educated, demanding professional career, higher socio-economic status, and development in assisted reproductive technology are contributed to this trend [6]. With the economic, technological, and social changes, the rate of giving birth at advanced maternal age (AMA, ≥ 35 years) has also significantly increased in China, especially in urban areas. As the national census data showed, the mean maternal age at first birth of Chinese women rose by 1.4 years, from 24.8 to 26.2 years between 2000 and 2010 [7]. Furthermore, a population-based study, which including all deliveries performed after 28 completed weeks of gestation within 2011 in 39 hospitals of 14 provinces in China, indicated the mean age for urban women childbirth was 28.18 years [8]. In addition, 10.1% of the urban women in that study were considered with AMA, which was near to the status of the western developed countries at the beginning of 20 th century [9, 10]. Many studies have shown that AMA is associated with increased incidence of maternal and fetal complications, including pregnancy-induced hypertension, gestational diabetes mellitus (GDM), amniotic fluid embolisms, as well as higher rates of elective cesarean section (CS) [8, 11-13]. In addition, perinatal morbidity and mortality, intrauterine fetal death (IUFD), and premature labor have also increased significantly for childbearing at AMA [8, 14, 15]. In previous studies, most have declared age 35 years as the cutoff for childbirth, after which the risk of adverse perinatal outcomes (stillbirth, perinatal and neonatal loss, low birth weight, and preterm birth) would increase. Meanwhile, some authors suggested that the association only becomes significant at the age greater than 40 years [16, 17]. Prior studies have however mainly focused on European and American populations investigation. The figures of childbearing delay for Asians are deficient [18]. So in this study, the authors carried out a retrospective research, to investigate the associations between adverse pregnancy outcomes and delivery age (≥35 years) in Chinese urban women and to compare the pregnancy outcomes for the women at very AMA of ≥ 40 years old with those aged between 35 and 39 years.