Is there any truth to the idea that more babies are born during a full moon?

As the full moon approaches, expectant mothers nearing their due dates often prepare for the possibility of going into labor. Many believe that the full moon can trigger childbirth—but is there any truth to this?

This belief is deeply rooted in history, with its origins lost in time. However, one thing is certain: cultures worldwide have long held a strong conviction in the moon's influence on human biology. Beyond childbirth, the moon's phases are also thought to impact conception, fertility, and even unrelated behaviors like crime rates, suicide rates, hospital visits, and mental health episodes. All of these are said to spike during a full moon. And, of course, there's the enduring myth of werewolves.

This phenomenon is known as the lunar effect. When it comes to births, the primary theory revolves around the moon's gravitational force. Just as the moon governs ocean tides, it is believed to influence the human body, which is composed of about 80% water. Additionally, since menstrual and ovulation cycles align roughly with the lunar month, it seems plausible that the moon could also play a role in the timing of childbirth.

But is there any truth to it? In this article, we’ll examine the evidence supporting and refuting the lunar effect on birth rates, and determine whether hospitals should prepare for busier shifts during full moons. We’ll also explore why this belief is so widespread.

If you relied solely on anecdotal accounts, the lunar effect would appear undeniable. Advocates claim that a simple survey in any hospital would confirm the link between full moons and an uptick in childbirth.

Anecdotal Proof for the Lunar Effect

When you inquire further, you’ll likely discover that most believers in the lunar effect base their conviction on anecdotal evidence—specifically, stories shared by medical professionals in obstetrics. Labor nurses, in particular, often provide firsthand accounts of increased admissions to delivery wards during full moons.

And who wouldn’t trust a labor nurse? They are, without a doubt, experts in the field of childbirth. However, as we’ll explore on the next page, anecdotal evidence like this is often highly unreliable for several reasons.

That said, there is some limited empirical evidence supporting the lunar effect. A 1959 study divided the month into three-day intervals and discovered that the "full moon window"—the day before, during, and after a full moon—had the highest number of births compared to any other three-day period [source: Shulman]. Similarly, a 1966 study analyzed birth rates across moon phases—full, half, one-quarter, and three-quarter—and found that births peaked during the full moon phase [source: Shulman].

However, as you delve deeper into the scientific research on the connection between births and full moons, it becomes evident that these studies supporting the lunar effect are outliers. The overwhelming majority of evidence suggests that the lunar effect is a myth rather than a scientific fact.

At times, studies are even misinterpreted by those who believe in the lunar effect. For example, an article on the website BirthSource includes the following statement:

However, if you examine the abstract of the study referenced in the text [note: the article cites it as reference "5," but it actually refers to reference "3"], you’ll find the following conclusion:

So, what does this mean for the lunar effect theory?

Statistical Evidence Against the Lunar Effect

Beyond anecdotal accounts and rare statistical anomalies, there is little evidence to support the claim that more babies are born during a full moon. Despite extensive research on the topic, the majority of studies easily disprove any connection between the two.

Here are just a few examples of scientific studies that have found no link between full moons and birth rates:

1957: Analyzed periods with unusually high birth rates and attempted to link them to full moons. No connection was established [source: Shulman].

1987: Examined U.S. birth rates over several decades and found no relationship between full moons, birth rates, or conception rates [source: Shulman].

1996: Reviewed 100 prior studies on lunar effects and found no statistically significant evidence linking the moon to births, violence, suicides, major disasters, or other phenomena often attributed to lunar cycles [source: Skeptic's Dictionary].

1998: Analyzed 3,706 births and concluded that "scientific evaluation of the data does not support the idea that births increase as the full moon nears, making it a myth rather than a fact" [source: ScienceDirect].

2005: Studied 564,039 births in North Carolina from 1997 to 2001 and found "no predictable impact of the lunar cycle on deliveries or complications" [source: PubMed].

2006: Examined births over a 28-year span in Australia and determined that "full moons are not linked to any notable changes in conceptions, births, or deaths" [source: Gans].

With so much evidence contradicting the lunar effect, why does this belief persist? The reasons are similar to why many old wives' tales or urban legends gain traction: it’s a compelling and easy idea to accept.

Cognitive Bias and the Full Moon Birth Myth

The idea that more babies are born during a full moon is deeply rooted in cultural traditions. Folklore, by its very nature, has been around for so long that it often feels like common knowledge. Challenging a belief that has been handed down through generations can feel counterintuitive.

It’s also difficult to dispute the claims of professionals like labor nurses and paramedics. After all, who would have more firsthand experience?

Additionally, the media’s fascination with the mysterious full moon plays a role. News outlets love sensational stories about full moons causing overcrowded labor wards or paramedic shortages, while Hollywood thrives on the classic image of a werewolf howling at the moon.

Cognitive bias also significantly contributes to this belief. Cognitive bias is a psychological tendency where people focus on evidence that confirms their beliefs while disregarding anything that contradicts them. For example, a nurse might remember every busy shift during a full moon but overlook the times when the ward was quiet.

Lastly, there are some common misunderstandings about the moon. For example, a full moon technically lasts only a moment; the idea of a "full moon window" spanning three days, or even one day, is a human-made concept [source: Shulman]. Additionally, while many assume the moon’s gravity is exceptionally strong due to its influence on tides, it’s actually relatively weak and unlikely to impact the human body [source: Skeptic's Dictionary]. Moreover, the gravitational force affecting tides isn’t tied to the moon’s phase—it depends on the moon’s distance from Earth at any given time, which is unrelated to its phase [source: Skeptic's Dictionary].

But don’t worry—there’s still one lunar-effect belief we can hold onto: there’s no solid proof that the moon doesn’t influence werewolves.