AUTHOR=Tang Wenyi , Zou Lingyun 

TITLE=Trends and characteristics of multiple births in Baoan Shenzhen: A retrospective study over a decade

JOURNAL=Frontiers in Public Health

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2022.1025867

DOI=10.3389/fpubh.2022.1025867

ISSN=2296-2565

ABSTRACT=Background: Shenzhen has the largest and youngest foreign population among all cities in China. The reproductive health of pregnant women from different backgrounds is a social issue that deserves attention. In the past decade, China has liberalized its population policies to stimulate population growth, and the proportion of multiple births has continued to increase.
Method: This retrospective cohort included 526,654 newborns born in Baoan, Shenzhen, from January 1, 2009, to December 31, 2019, including 515,016 singletons and 11,638 twins or triplets. Univariate regression models were used to analyse the effects of maternal sociodemographic characteristics, physiological characteristics, medical history, antenatal care and other factors associated with single versus multiple births and to elucidate the changing trends of different factors affecting multiple births in the past eleven years. 
Results: The rates of pregnancy complications, preterm birth, and advanced-age pregnancy were significantly higher in the multiple birth mothers than in single birth mothers, and more multiple pregnancies were achieved through assisted reproductive technologies. The rates of adverse outcomes such as stillbirth, malformation, hypoxia, and ultralow body weight in multiple foetuses were significantly higher than that in singleton foetuses. The trend analysis from 2009-2019 showed that the socioeconomic status and health level of mothers with multiple births improved over time, and the risk during pregnancy generally decreased. Simultaneously, the development indicators of multiple foetuses have improved year by year, and the proportion of adverse outcomes has also decreased significantly. A low prenatal care utilization rate was shown to be detrimental to the development of multiple foetuses. Independent risk factors for hypoxia and very low birth weight were also identified. The differences in secular trends  were further revealed by time series models.
Conclusion: This study presented a comprehensive survey of multiple pregnancies in the area with the largest population inflow in China. This study identified the factors that affect the health of multiple birth mothers and their foetuses, particularly suggesting that preterm birth rates and the use of assisted reproduction remain high. The findings provide a basis for the formulation of individualized prenatal care, assisted reproductive guidance and health care policies for multiple births.