You may have encountered the concept that the increase in the number of boys born after wars can be perceived as a form of divine intervention or karmic response to those who lost their lives in battle.

However, this phenomenon isn’t restricted to wartime. Significant stressors in a nation’s history, such as natural disasters, famine, or collective mourning periods, can also impact male birth rates.

For instance, a study led by Maltese pediatrician Professor Victor Grech in 2015 revealed that the birth rate of boys in the UK temporarily dipped following the death of Princess Diana.

These fluctuations might be connected to the established link between stress and miscarriage rates. Recent research indicates that miscarriages affect female fetuses slightly more than male ones.

But why exactly is this the case? It remains unclear.

Yet, female embryos appear to be particularly vulnerable during the first trimester, leading to an increased risk of repeated miscarriages.

Therefore, during times of heightened stress—like wartime—the increased frequency of miscarriages might contribute to a skewed sex ratio favoring boys.

Additionally, another factor influencing the rise in male births post-war is that overall birth rates tend to surge when soldiers return home. This is often attributed to increased intimate activity among couples.

But why does this result in more boys? The theory suggests that male births occur slightly more often when conception happens at the onset or end of the menstrual cycle, while female births are more likely to occur when conception happens mid-cycle.

As couples engage in sexual activity more frequently, they may conceive during the “male” days of the cycle. This leads to a slight but noticeable increase in male births when many couples are intimate.

While this difference isn’t significant enough for those trying to conceive a specific sex, in the context of hundreds of thousands of births, it could help adjust the overall sex ratio.

This article answers the question posed by Nicole Porter via email: “What is the veteran effect? Is it true?”

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