The sex ratio at birth - Historical aspects

Income, stress, and sex ratios over 1895-2010

The medical literature has shown that populations under high stress have a lower sex ratio at birth (i.e. number of males for every 100 females). In this paper, I examine the relationship between income, as a source of economic stress, and the sex ratio at a subnational level for the 1895-2010 period. For this, I use census microdata from Argentina -a developing country that experienced rapid growth at the end of the 19th century and stagnated in recent decades- and I estimate from a two-way fixed effects model that exploits the wide temporal and geographic variability in income. The results show that as per capita income increases, the sex ratio at birth also increases. In particular, for every US$ 1,000 increase in per capita income, the sex ratio increases between 0.3 and 0.6 points. These findings make it possible to quantify the lost boys (i.e. those boys who were not born due to high economic stress on their parents) and constitute a call for attention in favor of the implementation of prenatal care policies -especially in periods of stagnation or income decline- to maintain a more balanced sex ratio.

How does the two-child policy affect the sex ratio at birth in China? A cross-sectional study

BACKGROUND

The One-Child Policy led to the imbalance of the sex ratio at birth (SRB) in China. After that, Two-Child Policy was introduced and gradually liberalized at three stages. If both the husband and wife of one couple were the only child of their parents, they were allowed to have two children in policy (BTCP). If only one of them was the only child, they were allowed to have two children in policy (OTCP). The Universal Two-Child Policy (UTCP) allowed every couple to have two children. The objective of this study was to explore the changing trend of SRB at the stages of Two-Child Policy, to analyze the effect of population policy on SRB in terms of maternal age, delivery mode, parity, maternal education, delivery hospital, and to figure out what factors have greater impact on the SRB.

METHODS

The data of the study came from Hebei Province Maternal Near Miss Surveillance System, covered the parturients delivered at 28 gestation weeks or more in 22 hospitals from January 1, 2013 to December 31, 2017. We compared the SRB at different policy stages, analyzed the relationship between the SRB and population policy by logistic regression analysis.

RESULTS

Total 270,878 singleton deliveries were analyzed. The SRB, 1.084 at BTCP, 1.050 at OTCP, 1.047 at UTCP, declined rapidly (χ² = 15.97, P < 0.01). With the introduction of Two-Child Policy, the percentage of parturients who were 30-34, ≥35 years old rose significantly, and the percentage of multiparous women increased significantly (40.7, 47.2, 56.6%). The neonatal mortality declined significantly (8.4‰, 6.7‰, 5.9‰, χ² = 44.49, P < 0.01), the mortality rate of female infant gradually declined (48.2, 43.7, 43.9%). The logistic regression analysis showed the SRB was correlated to the three population policy stages in terms of maternal age, delivery mode, parity, maternal education, delivery hospital.

CONCLUSIONS

The SRB has declined to normal level with the gradually liberalizing of Two-Child Policy in China. Advanced maternal age, cesarean delivery, multiparous women, middle level education, rural hospital are the main factors of effect on the decline of the SRB.