Model Inputs \(\rightarrow\) Family Planning Parameters \(\rightarrow\) Sex Ratio - Secondary
The secondary sex ratio is the ratio at birth (males/females), which may be higher than the primary sex ratio due to sex-selective abortion, driven by factors such as son preference, readily available technology of prenatal sex determination, and fertility decline.[1,2] In the model, the difference between the secondary and primary sex ratio in each country is used to modify the probability of abortion for female fetuses.
The UN World Population Prospects 2022 includes estimates of sex ratio at birth for each country over time.[3] Estimates range from 1.0 to nearly 1.2 in countries such as China and Azerbaijan where sex-selective abortion may be more prevalent.
To estimate priors we fitted hierarchical models by region to trends in the estimated secondary sex ratios between 1990 and 2020.
The difference between the primary and secondary sex ratio is used to modify the risk of abortion for female fetuses. (Note: This only applies to singleton pregnancies in the model.) To estimate the relative risk of sex-selective abortion based on these ratios, let \(\rho_1\) by the primary sex ratio \(\frac{m_1}{f_1}\), and \(\rho_2\) by the secondary sex ratio \(\frac{m_2}{f_2}\). Let \(\pi\) by the probability of abortion for males. We then have \(\rho_2=\frac{m_1*(1-\pi)}{f_1*(1-\pi*\alpha)}\), where \(\alpha\) is the relative risk of abortion for females. Solving for \(\alpha\) we have
\[ \alpha=\frac{\pi+r-1}{r\pi} \] where \(r=\frac{\rho_2}{\rho_1}\).
We enforced a floor of 1.0 for the relative risk of sex-selective abortion (\(\alpha\)).
GMatH (Global Maternal Health) Model - Last updated: 28 November 2022
© Copyright 2020-2022 Zachary J. Ward
zward@hsph.harvard.edu