A review of terrorism and its reduction of the gender ratio at birth after seasonal adjustment

Outcome of the 2016 United States presidential election and the subsequent sex ratio at birth in Canada: an ecological study

“…From the perspective of evolutionary biology, it has been suggested that, under adverse conditions, the loss of frail male fetuses may be beneficial to the species by yielding a ‘culled cohort’ of healthier males that are better able to reproduce and hence increase the likelihood of survival of the population 5 6 24. Among such societal stressors in humans, discrete events such as terrorist attacks have typically induced a characteristic pattern consisting of a transient decline in the sex ratio 3–5 months later that is believed to reflect comparatively greater male fetal loss during a vulnerable window in mid-pregnancy at around 20–25 weeks' gestation 10 17. In other words, the greater loss of male fetuses who are within this vulnerable window at the time of the event results in a depression of the sex ratio 3–5 months later when these babies would otherwise have been born.…”

“…It is known that the sex ratio is subject to seasonality,10 18 therefore we used box plots of the time series of sex ratio by month to examine a possible seasonal pattern. An autoregressive integrated moving average (ARIMA) model-based seasonal adjustment method Tramo (time series regression with ARIMA noise, missing values and outliers)19 20 was implemented with PROC X12 in SAS to remove the seasonal component from the time series.…”

“…Notably, discrete events, such as terrorist attacks, have typically resulted in a temporary decline in the sex ratio 3–5 months after the event, followed by recovery over around 5 months thereafter 10 13–17. This pattern has been seen after a range of events, including the September 11, 2001 attacks,13–15 the 2004 Madrid bombings,10 17 the 2005 London bombings,10 17 the 2011 Norway attacks,16 and the 2012 Sandy Hook Elementary School shooting 16. Moreover, this characteristic pattern of the sex ratio in the months thereafter has been confirmed in a meta-analysis assessing the effect of these events on the sex ratio at birth 17…”

“…Indeed, adverse societal stressors such as natural and man-made disasters,7–10 economic downturn,11 social unrest,10 12 and terrorist attacks10 13–17 have all been reported to decrease the proportion of boys at birth, likely reflecting greater spontaneous loss of male fetuses in response to these conditions 5 6. Notably, discrete events, such as terrorist attacks, have typically resulted in a temporary decline in the sex ratio 3–5 months after the event, followed by recovery over around 5 months thereafter 10 13–17. This pattern has been seen after a range of events, including the September 11, 2001 attacks,13–15 the 2004 Madrid bombings,10 17 the 2005 London bombings,10 17 the 2011 Norway attacks,16 and the 2012 Sandy Hook Elementary School shooting 16.…”

“…As there is no conclusive evidence of variability in the sex ratio at conception,1 such variation in the analogous ratio at birth is believed to reflect sex-specific differences in the likelihood of fetal demise at various times during pregnancy 5 6. Indeed, adverse societal stressors such as natural and man-made disasters,7–10 economic downturn,11 social unrest,10 12 and terrorist attacks10 13–17 have all been reported to decrease the proportion of boys at birth, likely reflecting greater spontaneous loss of male fetuses in response to these conditions 5 6. Notably, discrete events, such as terrorist attacks, have typically resulted in a temporary decline in the sex ratio 3–5 months after the event, followed by recovery over around 5 months thereafter 10 13–17.…”