Did China’s two-child policy change birth defects?
In 1.26 million Zhejiang births, advanced maternal age nearly doubled after the two-child policy and total birth-defect prevalence rose, especially chromosomal anomalies.
Source
Changes in maternal age and prevalence of congenital anomalies during the enactment of China's universal two-child policy (2013-2017) in Zhejiang Province, China: An observational study
Study at a glance
- Design
- Cross-sectional — Serial hospital-based birth-defect surveillance comparing one-child, partial two-child, and universal two-child policy periods in Zhejiang
- N
- N=1260684 · 1,260,684 births (live births, early fetal losses, stillbirths, early neonatal deaths) across 2009–2017 surveillance years
- Population
- Births captured by Zhejiang Province BD surveillance covering 90 hospitals (about one-third of provincial births)
- Outcome
- Maternal age distribution, prevalence and ranking of birth defects, prenatal diagnosis timing, and live-birth rate of BDs before 28 weeks
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Inspect source passages
Did China’s two-child policy change birth defects?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
1,260,684 births were included in the analyses.
A total of 1,260,684 births (including live births, early fetal losses, stillbirths, and early neonatal deaths) were included in the analyses.
Births to women ≥35 years rose 85.68%, from 8.52% in 2013 to 15.82% in 2017.
The proportion of births to women aged ≥35 years increased by 85.68% with policy changes, from 8.52% in 2013 to 15.82% in 2017
What they did
Compared BD surveillance years representing the one-child (2013), partial two-child (2015), and universal two-child (2017) periods, using 90 hospitals covering about one-third of Zhejiang births, and also showed pre-policy age trends (2009, 2011).
What they found
Births to mothers ≥35 rose 85.68% (8.52% in 2013 to 15.82% in 2017). BD prevalence rose from 245.95 to 304.36 per 10,000 births. Trisomy 21 crude OR was 2.13; other chromosomal defects OR 3.63. Live birth of BDs before 28 weeks rose from 1.29% to 11.45%.
The limits
What it doesn't show
Observational surveillance cannot prove the policy caused defects; unknown confounders and changing prenatal detection may contribute.
Key terms
- Birth defects (BDs)
- Structural or functional congenital anomalies in a fetus or newborn.
- Advanced maternal age
- Maternal age 35 years and older at birth.
- Universal two-child policy
- China’s 2015 policy allowing all couples a second child.
- Prenatal diagnosis
- Detection of BDs before birth, here occurring earlier over time.
- Trisomy 21
- Down syndrome; chromosomal BD that rose in ranking after the policy.
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Common questions
How many births were analysed?
1,260,684 births in Zhejiang BD surveillance.
How much did advanced maternal age increase?
85.68%, from 8.52% (2013) to 15.82% (2017).
What happened to BD prevalence?
245.95 (2013) to 304.36 (2017) per 10,000 births.
Can this prove the policy caused BDs?
No; observational data cannot establish causality.
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