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

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.

Fig 1

Number of births in mainland China during January 2014 and December 2017, by month (information taken from county level monthly aggregated data). Both selective and universal two child policies were assumed to take effect about nine months after being announced. The year of the sheep in the Chinese calendar, falling between February 2015 and February 2016, is considered to be a particularly unlucky time of birth

Fig 2

Number of births to nulliparous and multiparous mothers in mainland China, by month (January 2015 to December 2017). Births to nulliparous and multiparous mothers were estimated using the strategy described in the methods. Hypothetical births to multiparous mothers (that is, assuming that the policy had not been introduced) were calculated by subtracting the mean difference between births to nulliparous mothers and those to multiparous mothers during the baseline period (January 2015 to June 2016) from the number of nulliparous births at each month (July 2016 to December 2017)

Fig 3

Secular trends in percentage of multiparous mothers (top) and mothers aged 35 and over (bottom) in mainland China from January 2015 to December 2017, based on data from individual level delivery information records. Dotted yellow line=mean monthly percentage of multiparous mothers during January 2015 to June 2016 (46.4%; top) or mean monthly percentage of mothers aged 35 and older during January 2015 to June 2016 (8.5%; bottom)

Fig 4

Monthly trends in overall and parity specific rates of caesarean delivery in mainland China, from January 2016 to December 2017, based on data from individual level delivery information records