Preplanned Studies: Changes in Maternal Socio-Demographic Characteristics and Pregnancy Outcomes Across Monitoring Regions — Six Provinces, China, 2016–2022

In recent years, China has faced significant challenges due to a declining fertility rate, an aging population, and an unbalanced demographic structure. Concurrently, there have been shifts in maternal characteristics and pregnancy outcomes. While existing research predominantly focuses on maternal age and pregnancy results and often only within specific provinces (1–4), there remains a lack of comprehensive understanding of socio-demographic traits across various regions. This retrospective study examines maternal data from monitoring sites across China from 2016 to 2022, providing a systematic evaluation of the changes in maternal socio-demographic characteristics and perinatal outcomes. The findings reveal that from 2016 to 2022, there was an increase in the number of advanced maternal age (AMA) mothers, educational attainment, and instances of preterm birth and low birth weight (LBW) among both primiparous and multiparous mothers. Conversely, the rates of cesarean delivery and macrosomia among multiparous mothers showed a declining trend. These trends underscore the need for targeted healthcare improvements and policies encouraging childbirth at optimal ages to mitigate adverse pregnancy outcomes.

Data for this study were obtained from the Maternal and Newborn Health Monitoring System (MNHMS), established by the National Center for Women and Children’s Health (NCWCH) in 2013. The cohort comprised all pregnant women who were either resident or had resided for more than six months in the designated monitoring areas and were enrolled during their initial antenatal care (ANC) visit. Data, including ANC visits throughout pregnancy and delivery, were captured and maintained in the MNHMS. To ensure data continuity and integrity, this study analyzed maternal case data from 6 provinces monitored from January 1, 2016, to December 31, 2022. The regions covered included Fujian Province (Haicang and Jimei districts) and Guangdong Province (Zijin and Longchuan counties) in the eastern region, Hebei Province (Zhengding County) and Hubei Province (Luotian County) in the central region, and Sichuan Province (Gongjing District and Rong County) and Yunnan Province (Tonghai and Huaning counties) in the western region. Inclusion criteria were: 1) delivery occurred between January 1, 2016 and December 31, 2022; 2) singleton pregnancies; and 3) live birth. Exclusion criteria included: 1) missing last menstrual period (LMP) or delivery dates; 2) availability of only prenatal examination records or absence of delivery records. Ultimately, 253,389 pregnant women and their infants were included in the analysis. The Maternal and Newborn Health Monitoring Program (MNHMP) data collection was approved by the Ethics Committee of the National Center for Women and Children’s Health, China CDC (No. FY2015–007), and underwent annual ethical reviews (Nos. FY2018-14, FY2019-12, FY2021-13, FY2022-11). Additionally, the use of data in this study was also approved by this committee (No. FY2024-12).

In this study, women residing in the district were categorized as urban residents, while those living in the county were classified as rural residents. Preterm delivery was defined as childbirth occurring between 28 and less than 37 weeks of gestation, and LBW was defined as a birth weight below 2,500 g. The dataset was imported from Excel into SAS software (version 9.4, SAS Institute, Cary, NC, USA) for data cleaning. The $ {\chi }^{2} $ test was employed to evaluate differences between primiparas (first-time mothers) and multiparas (mothers with one or more previous births). The trend $ {\chi }^{2} $ test was utilized for univariate analysis to assess trends in maternal age, literacy, preterm birth, LBW, and macrosomia incidence annually.

In the monitored regions, the majority of mothers were aged between 18 and 34 years (88.9%). The proportion of women aged 35 years or older was significantly higher among multiparas (16.0%) compared to primiparas (3.9%). Educational attainment differed between the groups; 43.6% of primiparas had at least a college degree, and 30.9% had completed high school or vocational training. In contrast, the largest segment of multiparas had reached junior high school education (39.5%). Vaginal delivery was the predominant mode of delivery for both primiparas (63.8%) and multiparas (61.4%). The rates of preterm birth and macmultiparas (mothers with one or more previous births). The trend thers, whereas primiparous mothers experienced a significantly higher incidence of LBW compared to multipar test was utilized for univariate analysis to assess trends in maternal age, literacy, preterm birth, LBW, and macrosomia incidence annually (Table 1).

From 2016 to 2022, there was a significant increase in the proportion of AMA among both primiparas and multiparas, with all P<0.01. Specifically, the rise in the proportion of advanced age among multiparas (6.8%) was significantly greater than that among primiparas (2.4%). By 2022, the share of advanced-age multiparas peaked at 19.7%. Over the same period, the proportions of both primiparas and multiparas in eastern areas showed a consistent annual increase ($ {\chi }_{trend}^{2} $=4,625.873, P<0.01 and $ {\chi }_{trend}^{2} $=4,912.240, P<0.01, respectively). Additionally, from 2016 to 2022, there was a rising trend in the proportion of individuals with a college degree or higher among both primiparas and multiparas ($ {\chi }_{trend}^{2} $=2,757.522, P＜0.01 and $ {\chi }_{trend}^{2} $=1,896.743, P<0.01, respectively). From 2018 to 2022, the predominant educational level among primiparas was college or above. Among multiparas, although the predominant educational level was junior high school from 2016 to 2020, the proportion with college degrees or higher grew to become the majority by 2021 (38.1%) and further increased in 2022 (41.4%).

From 2016 to 2022, the distribution of delivery methods among primiparas remained largely unchanged. However, there was a notable decrease in the proportion of cesarean sections among multiparas ($ {\chi }_{trend}^{2} $=16.358, P<0.01). During the same period, the incidence of adverse pregnancy outcomes such as preterm birth and LBW increased among both primiparas and multiparas (all P<0.01). Conversely, the incidence of macrosomia in multiparas showed a declining trend ($ {\chi }_{trend}^{2} $=8.231, P<0.01) (Table 2).