First comes pollution, then comes … baby?

Jonathan Drake | Bloomberg | Getty Images

The air pollution from forest fires in Indonesia may be trailing off, but months of being cooped up inside might give Singaporeans something that outlives the haze: a new baby.

Analysts have long pointed to small baby booms nine months after severe weather or blackouts in the U.S. and although Indonesia's forest fires are an annual event, this year, the air pollution, colloquially called "the haze," has been particularly severe and long-lived due to an El Nino weather system causing less rain.

Singapore's air quality began to worsen in August, first entering unhealthy levels in September and remaining there through much of October, although breathing in November has become a less gritty experience. Escaping the haze meant staying indoors.

"Keeping people indoors certainly would be a conducive environment as far as babies are concerned," Song Seng Wun, an economist at CIMB Private Banking, said in a phone interview. "We'll wait and see."

There could be an additional fillip: Travel out of Singapore got a big boost during the haze period. Travel search website Skyscanner said that searches for outbound travel from Singapore climbed gradually from September 4 - when the city-state's air quality levels started approaching an unhealthy level - and by October 23 were more than 50 percent higher.

The Singapore Flyer Ferris wheel, right, stands shrouded in smog in Singapore, on Thursday, Sept. 24, 2015.
This sector is enjoying a haze-related boost

"People leaving on the plane and having vacations in exotic locations like Phuket and Bali" might just cast aside some inhibitions, he noted. Alcohol -- which is pricey in Singapore, but much cheaper in nearby Thailand and Indonesia -- could help, Song said.

Singapore's birth statistics offer only limited indication that previous bad episodes of haze were followed by a rise in births nine months later.

In June of 2013, Singapore's Pollutant Standards Index, a global gauge of air quality, climbed over 400 for the first time ever and air quality in the city-state remained poor into July. A level between 100 and 200 indicates unhealthy air quality, while levels above 300 are considered hazardous.

Around nine months later, in the second and third quarters of 2014, births were 8-10 percent higher than in the year-earlier periods at 10,466 and 10,670, respectively.

After another bad haze episode in October and November of 2006, when PSI readings crossed over 100, births in the third quarter of 2007 climbed around 5 percent from the year-earlier period to their highest since 2002.

The 1997 haze -- at the time, the worst ever with PSI peaking around 226 in September -- is a bit of a sticky wicket, with births in the third quarter of 1998 actually dropping. But other factors may be in play: In 1997, Singapore was suffering from the Asian Financial Crisis, with its property bubble popping. It's not a situation likely to spur couples to throw all caution to the winds.

A pedestrian wearing a face mask at Marina Bay in Singapore, on Thursday, Sept. 24, 2015.
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To be sure, correlation isn't causation and there are plenty of alternate explanations for birth-rate fluctuations, especially in Singapore, which has a majority ethnic Chinese population.

"Haze stretches over a long period. (It's) probably not a strong one-off stimulus," noted Paul Cheung, a professor of social policy and analytics at the National University of Singapore and a former director of the United Nations' statistics division.

The rebound in births in 2014 might also be related to the Chinese zodiac, he said via email.

"2012 was 'Dragon Year' with much higher number of births. 2013 was much lower due to shifts in timing. There was a slight rebound in 2014," he said. However, while births spiked up in the second and third quarters of 2012, excluding those periods, 2014's third quarter had the highest number of births in any quarter since 2007.

Cheung doesn't expect a haze-related baby boom, noting that Google analytics show pregnancy-related searches aren't on the rise. Of course, the impact of any special occasions in October might not yet be apparent. But Cheung expects births will rise next year anyway as the government has introduced fresh benefits for families.

The Chinese calendar could be affecting birth rates in another way: births tend to be higher in the fourth quarter, around nine months after the Chinese New Year holidays, when many of the city-state's businesses are shuttered.

The government will likely be happy for any boost to the birth rate, no matter the cause. Singapore's fertility rate was only 1.2 births per woman in 2013, according to World Bank data. That's not just below the replacement rate of 2.1, it's below even famously aging Japan's rate of 1.4 and puts the city-state only fourth from last globally.

Singapore's government has long pushed its citizens toward getting in the family way. In addition to arranging speed-dating sessions to help encourage family-making, Singapore's Ministry of Community Development Youth and Sports offers funding to start dating agencies and has accredited 12 of them to ensure they meet quality standards.

The government also offered incentives to babies born this year, the city-state's 50th anniversary of becoming an independent nation, as well as fresh benefits, such as government-paid paternity leave.

Anecdotally, it seems to be working.

"We are seeing a little bit more strollers on the streets and trains these days," CIMB's Song noted.

There's another reason to not be sure the haze would instigate a baby boom: It's not even entirely clear that events, such as bad weather and blackouts, really do cause happy events nine months later.

A 2007 study by academics Richard W. Evans, Yingyao Hu and Zhong Zhao examined storm advisory and fertility data for the Atlantic and Gulf-coast regions in the U.S. Their conclusion on whether there are weather-related baby booms: It depends.

Low-severity storm advisories tended to have a significant positive fertility effect, while high-severity ones had a negative effect, they said, noting that other studies' attempts to find a link have met with mixed results.

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The academics even have a theory for why a low-level advisory is different.

"During a low-level advisory, people might spend more time at home, leading to more sexual activity because the opportunity cost of leisure is lower," they said. "During a high-level advisory, the opportunity cost of leisure increases, and individuals are more likely to be occupied by other precautionary activities."

There's another issue, they noted: in a low-level advisory, obtaining a contraceptive could be relatively costly and high risk, while during a high-level one, people will likely be shopping for necessities anyway.

It's not clear any of that applies to Singapore's recent bout of haze. Going outdoors during poor air quality days may be uncomfortable, but it may not prevent anyone from popping down to their neighborhood grocery store.

Indeed, during the most recent bout of haze, rather than staying at home, many people packed the city-state's malls on days the air quality was poor, taking advantage of commercial-strength air-conditioners and air-purifiers.

Not staying home could put a damper on any potential baby boom.