北医三院乔杰小组和北大医学部刘建蒙小组，分析了中国全面二孩政策与出生率及生育相关健康因素变化的关系。相关论文于2019年8月22日在线发表于《英国医学杂志》。

2015年10月，中国颁布了全面二孩政策，旨在改善人口增长停滞、人口老龄化和劳动力萎缩的状况。该政策的目标人群是约9000万育龄女性，她们已生育一胎，2015年10月以后被允许生育二胎。

该研究分析了中国大陆31个省份中28个省份的生育记录，2014年1月至2017年12月，出生总人口为67786749人。

2016年7月至2017年12月，二孩政策导致的额外出生人口数量为540万。经产妇和35岁以上产妇的月平均百分比分别增加了9.1个百分点和5.8个百分点。然而，高龄产妇的增多并未引起早产率的增加。经产妇的月平均剖腹产率从39.7%上升到40.9%，上升了1.2个百分点，而初产妇的月平均剖腹产率从39.6%下降到36.6%，下降了3.0个百分点。

综合来看，2015年10月以来，全面二孩政策提高了中国的出生率，生育妇女更有可能是经产妇和35岁以上产妇，同时未发现早产率显著增加。

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附：英文原文

Title: Association of China’s universal two child policy with changes in births and birth related health factors: national, descriptive comparative study

Author: Hong-tian Li, associate professor,  Ming Xue, senior statistician,  Susan Hellerstein, assistant professor,  Yue Cai, associate professor,  Yanqiu Gao, lecturer,  Yali Zhang, assistant professor,  Jie Qiao, professor,  Jan Blustein, professor,  Jian-meng Liu, professor

Issue&Volume: 21 August 2019

Abstract:

Objective To measure the association of China’s universal two child policy, announced in October 2015, with changes in births and health related birth characteristics.

Design National, descriptive before-and-after comparative study.

Setting Every county in 28 of 31 provinces of mainland China.

Participants Births included in two national databases: 67 786 749 births from county level monthly aggregated data between January 2014 and December 2017; and 31 786 279 deliveries from individual level delivery information records between January 2015 and December 2017.

Main outcome measures Monthly mean number of births and mean proportion of multiparous mothers and mothers aged 35 and over, preterm deliveries, and caesarean deliveries.

Results The study had two phases: the baseline period (up to and including June 2016, nine months after the policy announcement) and the effective period (from July 2016 to December 2017). The estimated number of additional births attributable to the new policy between July 2016 and December 2017 was 5.40 million (95% confidence interval 4.34 to 6.46). The monthly mean percentage of multiparous mothers and mothers aged 35 and over increased by 9.1 percentage points (95% confidence interval 6.4 to 11.7) and 5.8 percentage points (5.2 to 6.4), respectively. This increase in older mothers, however, was not associated with a concurrent increase in the overall rate of preterm birth. The monthly mean caesarean delivery rate among multiparous mothers increased by 1.2 percentage points (0.8 to 1.6) from 39.7% to 40.9%, and decreased by 3.0 percentage points (−3.5 to −2.5) among nulliparous mothers from 39.6% to 36.6%.

Conclusions Since its announcement in October 2015, the universal two child policy has been associated with a rise in births in China and with changes in health related birth characteristics: women giving birth have been more likely to be multiparous, and more likely to be aged 35 and over. No evidence of concurrent worsening outcomes (that is, premature births) was seen.

DOI: https://doi.org/10.1136/bmj.l4680

Source: https://www.bmj.com/content/366/bmj.l4680