Association of China's two-child policy with changes in number of births and birth defects rate, 2008-2017

Abstract

Background: In October 2015, China's one-child policy was universally replaced by a so-called two-child policy. This study investigated the association between the enactment of the new policy and changes in the number of births, and health-related birth outcomes.

Methods: We used difference-in-difference model to analyse the birth record data in Pudong New Area, Shanghai.The design is descriptive before-and-after comparative study.

Results: The data covered three policy periods: the one-child policy period (January 2008 to November 2014); the partial two-child policy period (December 2014 to June 2016); the universal two-child policy period (July 2016 to December 2017). There was an estimate of 7656 additional births during the 18 months of the implementation of the universal two-child policy. The trend of monthly percentage of births to mothers aged ≥35 increased by 0.24 percentage points (95% confidence interval 0.19 to 0.28, p < 0.001) during the same period. Being a baby boy, preterm birth, low birth weight, parents with lower educational attainment, and assisted delivery were associated with a higher risk of birth defects.

Conclusions: The universal two-child policy was associated with an increase in the number of births and maternal age. Preterm birth, low birth weight, and assisted delivery were associated with a higher risk of birth defects, which suggested that these infants needed additional attention in the future.

Keywords: Birth defects; Birth outcomes; Difference-in-difference model; Number of births; Two-child policy.

Fig. 1

The number of monthly births in Pudong New Area, Shanghai. There were three policy periods: the one-child policy period (Jan 2008 - Nov 2014), the partial two-child policy period (Dec 2014 - Jun 2016), and the universal two-child policy period (Jul 2016 - Dec 2017). Policy was assumed to take effect about nine months after the announcement

Fig. 2

The estimated number of monthly births if the two-child policy had not been implemented. The purple line was the monthly number of nulliparous births; the yellow line was the monthly number of multiparous birth; the grey dashed line was the estimated number of multiparous birth if the two-child policy had not been implemented (For births with Shanghai and non-Shanghai household registration, the coefficients of parity*universal two-child policy was zero in the difference-in-difference model; For births with Shanghai household registration, the coefficients of parity*partial two-child policy and parity*universal two-child policy were zero); The area of the grey shading was estimated extra births during to China’s policy change

Fig. 3

The monthly percentage of births to maternal age ≥ 35

Fig. 4

The logistic regression model identifying the risk factors associated with birth defects