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When a baby cries at night, exhausted parents scramble to figure out why. He’s hungry. Wet. Cold. Lonely. But now, a Harvard scientist offers more sinister explanation: The baby who demands to be breastfed in the middle of the night is preventing his mom from getting pregnant again.This devious intention makes perfect sense, says evolutionary biologist David Haig, who describes his idea in Evolution, Medicine and Public Health. Another baby means having to share mom and dad, so babies are programmed to do all they can to thwart the meeting of sperm and egg, the theory goes.Since babies can’t force birth control pills on their mothers, they work with what they’ve got: Nighttime nursing liaisons keep women from other sorts of liaisons that might lead to another child. And beyond libido-killing interruptions and extreme fatigue, frequent night nursing also delays fertility in nursing women. Infant suckling can lead to hormone changes that put the kibosh on ovulation (though not reliably enough to be a fail-safe birth control method, as many gynecologists caution). Of course, babies don’t have the wherewithal to be interrupting their mothers’ fertility intentionally. It’s just that in our past, babies who cried to be nursed at night had a survival edge, Haig proposes.
                                                                                                                     
                                                                                                                            

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The timing of night crying seems particularly damning, Haig says. Breastfed babies seem to ramp up their  nighttime demands around 6 months of age and then slowly improve — precisely the time when a baby would want to double down on its birth control efforts.Genetic disorders that are inherited from mothers or fathers provide even more evidence. Babies who get certain genes from their mothers sleep longer in the night, which is in the best interests of a woman who wants to get pregnant again. But babies who get the same genes from their fathers wake up more often, delaying ovulation in their mothers, Haig writes. That makes evolutionary sense: Because fathers have no guarantee that the next baby will also be his, they (men and their genes) are presumably not interested in ovulation starting again.Haig’s work builds on a similar proposal published in 1987, and if it’s right, it means that breast-fed babies who cry at night might be showing the ultimate sibling rivalry. Unsurprisingly, Haig has received a lot of interest on his theory, from the general public (he just appeared on Fox News) and from other scientists, who wrote responses to his work in the same journal.In his comment, anthropologist James McKenna of the University of Notre Dame points out that infants may have evolved to wake up at night for all sorts of other good reasons. Babies can get too hot, or hungry, or they could just want a cuddle from mom. And babies aren’t always to blame for rousing: In one study, McKenna and colleagues found that 40 percent of babies’ night wakings were actually caused by mothers rustling around nearby. These wakings could easily have benefits for the baby that trump the birth control for mom, McKenna writes: Frequent wakings prevent the baby from slipping into too deep a sleep, which can be dangerous.  But if Haig is right, the little screamers are doing all they can to prevent another baby from coming along and ruining their good thing. That self-interest is in direct conflict with the mother’s evolutionary goal, which is to shove her genes into as many children as possible. These divergent goals, Haig says, are an overlooked part of child-parent relationships. “Mothers have evolved to maximize their numbers of surviving children, which is different from maximizing the survival of each individual child,” he says.
There’s no way to go back and test whether night nursing actually helped babies survive in the early chapters of our evolutionary history. Today’s babies are growing up in a world that doesn’t look much like the one in which this trick could have been useful.  “I think that it’s an adaptation for a world very different from the current world,” Haig says. Contraception, solid nutrition and good health care have probably removed modern babies’ drive to prevent another sibling. Although we’ll never know exactly why babies evolved to cry at night, Haig’s idea offers one interesting explanation. Whether he is right or not, there is another message lurking in this study, and it’s a message for modern parents: Babies who don’t breastfeed during the night and babies who take bottles don’t wake up as much during the night — and they don’t seem to be worse off for it, Haig says. That result implies that nursing throughout the night isn’t necessary. So moms shouldn’t beat themselves up if they don’t always heed the nighttime calls to breastfeed, Haig says.
“There’s a tendency to think of infants as incredibly fragile beings, and if you do just one thing wrong, they’re ruined for life,” Haig says. “That to me doesn’t make any evolutionary sense. They should be fairly robust and handle all sorts of variation in sleeping arrangements and feeding arrangements.” He wraps up our interview with a sentiment that I think all parents embrace: “Do what feels right for yourself.”

For some women, pregnancy comes with all sorts of travails: Nausea, headaches, back pain, cankles. Now, a study suggests a previously underappreciated one. Pregnancy makes women more likely to get into a serious car crash, scientists reported May 12 in the Canadian Medical Association Journal.  Although the numbers show a clear uptick in accidents during the second trimester of pregnancy, I’m not convinced that pregnancy, or its symptoms, is to blame.
Women drivers were 42 percent more likely to show up in the ER for treatment for a car crash while in their second trimester of pregnancy than before they were pregnant, a review of over half a million pregnant Ontario residents found. Pre-pregnancy, these women got into an average of 4.55 crashes per 1,000 people per year. (That’s about double the population average, probably because these women are younger than the average driver.)  During the second trimester, that number climbed to 6.47 accidents per 1,000 people per year, researchers found. No such increases were found for the first or third trimesters.
Small, momentary lapses of attention, perhaps exacerbated by pregnancy symptoms such as fatigue, stress and insomnia, may explain the crash spike, says study coauthor Donald Redelmeier of the University of Toronto. “About 50 percent of pregnant women describe episodes of absentmindedness during pregnancy,” Redelmeier says, and those brief lapses can be disastrous when driving.
But could a simpler explanation be driving the increase? I think so, and not just because I feel like pregnant women need a little bit of love. The study didn’t look at how often women were driving. That means that the results could be explained by the simple fact that women in their second trimester could be driving more than women earlier or later in pregnancy, making them more susceptible to crashes.

Pieces of the data seem to support this explanation: Post-baby crash rates plummeted. In the first few months with a crying, non-sleeping, demanding newborn, women got in way fewer accidents than before they were pregnant. Were these sleep-deprived moms all of a sudden paragons for safe driving? Doubtful, I say. Much more likely is that these women weren’t driving much. In my first few months with Baby V, we were almost exclusively pedestrians, a habit that drastically lowered my risk of a car crash.
In contrast, women in their second trimester might be driving more than usual. Sometimes called the honeymoon phase of pregnancy, the second trimester often brings an end to the worst of the first trimester nausea and a dose of extra special magic pregnancy energy. Countless doctor’s appointments, baby prepping errands, work projects and gym visits might compel an energetic pregnant woman to jump behind the wheel more than usual.
Another tidbit that supports this alternative explanation is that car accidents did not go up in pregnant women who lived in rural areas, says Rebecca Goldin, mathematician at George Mason University in Fairfax, Va., and director of STATS, a nonprofit statistical watchdog group. Overall, rural women had a higher rate of car crashes than urban women, but those rates didn’t climb with pregnancy. Women who live in the country have to drive — they can’t rely on public transportation to get them to their destination. But pregnant women in the city, who can rely on trains and buses to get around, might opt to take a car instead, increasing their time on the road and their chances of getting in an accident.
Another monkey wrench in the study data: Pregnant women might be more inclined to head to the ER when involved in a crash. “I think it’s quite believable that pregnant women would be more likely to want to be checked out, or have additional concerns about being in an accident, compared with women who aren’t pregnant,” Goldin says.  Because the study tallied up only women who went to the ER after a crash, the results might be influenced by pregnant women’s desire to play it safe.
These alternative explanations don’t make the spike in accidents and ER visits disappear. Whether these wrecks are caused by pregnancy symptoms or simply more driving, they are still dangerous, and perhaps avoidable, situations.
Simple road safety habits can go a long way to help minimize the risk of an accident, Redelmeier says. Don’t speed, wear a seatbelt, and obey traffic laws, he says. Those are good reminders for all drivers, not just pregnant ones.
One final thought: In case any overprotective dudes out there insist on taking the keys, consider the fact that men around the same age as the women in the study have an even higher risk of a car crash than pregnant women. So ladies, pregnant or not, keep the keys but, as always, drive carefully.

The origin of Kawasaki disease has been linked to a fungal toxin riding the wind from farmland in northeastern China to Japan. The disease affects young children and can cause inflammation of blood vessels and, in some cases, fatal heart disease. Its origins have been unknown for more than 40 years.
New computer simulations trace the origin of the toxin to northeastern China. Candida fungi, which has been linked to Kawasaki-like symptoms in mice, is also the most dominant fungal strain blowing in  the wind during Kawasaki season, researchers report May 19 in the Proceedings of the National Academy of Sciences.