Throughout history, many people have wondered whether there is an association between extreme weather and pregnancy and pregnancy outcomes. It may sound like the stuff of “old wives tales,” but some ideas are so widespread that scientific studies have put them to the test.
Let’s take a look at some of these ideas and whether weather truly can influence your pregnancy.
Barometric pressure and spontaneous laborOne of the first suppositions was that barometric pressure change affects pregnancy.
Barometric pressure is, simply put, the weight of the air above us. It changes based on factors such as ambient temperature, humidity, and altitude. Generally speaking, falling barometric pressure is associated with stormy, rainy weather while rising barometric pressure typically means nice weather and sunny skies are ahead.
It is widely thought that pressure differences between the outside and inside of your body can trigger symptoms within. The most common example is the changes in your ears when you are on a plane going in to land. People also talk about predicting rain based on knees and elbows aching. The pressure in the joints is different than the pressure outside the body – which may lead to those symptoms. Low barometric pressure may also trigger headaches due to pressure differences in your sinuses.
Among health care professionals and labor and delivery nurses, there is a strong belief that falling barometric pressure results in an increase of spontaneous rupture of membranes and increased rates of spontaneous labor. In one survey, three-quarters of L&D nurses believed there was an effect from the weather. Most professionals come to this conclusion after spending hours working on a labor and delivery unit. It just seems that L&D gets a little busier when the weather gets bad. And it seems plausible, especially given the other effects barometric pressure seems to have on our bodies.
Yet research has been unable to establish a firm scientific link between barometric pressure and spontaneous labor or rupture of the membrane.
It’s hard to get good scientific measurements of what has happened with respect to barometric pressure and the sequence of events around labor for a given individual. You have to look at the area in which the person is living, track the pressure changes, and understand how quickly those changes occurred.
While some studies suggest this phenomenon is in fact real, overall the results are inconclusive. Even if it is true, the magnitude of importance is probably low, given everything else that occurs in the body during pregnancy. There’s also nothing we can do to affect changes in barometric pressure, so it’s probably not worth worrying about too much.
High blood pressure and the temperatureResearchers have also looked at other medical conditions and their relationship with the weather.
Clearly there are some parts of the world that experience more significant seasonality than others. In India, for example, changes surrounding monsoon season have been studied for risk of pregnancy complications such as preeclampsia and eclampsia. One study showed that while the incidence of preeclampsia or high blood pressure that develops during pregnancy didn’t change between monsoon season and the dry season, the risk of eclampsia (the development of seizures) was significantly higher during the monsoon season.
This study found an association between monsoon season and the risk of eclampsia, but it did not find that monsoon season caused an increased risk of this condition. There’s a big difference. There could be many other things happening during that time of year contributing to the difference in rates of eclampsia.
Studies on this topic sometimes contradict each another, making it even more difficult to draw solid conclusions. For example, another study from Brazil looked at hypertensive disorders and found that in cooler months there was a higher likelihood individuals would have high blood pressure. This is in direct opposition to the study focused on India’s monsoon season, which was cooler and more humid than the rest of the year yet saw fewer cases of high blood pressure in pregnancy.
How hot is too hot?There’s also the issue of heat tolerance. If you’ve lived in a community where there’ve been high temperatures for years and you’re accustomed to them, will extreme heat episodes affect you in the same way as they would someone who, say, just moved from Alaska to Dallas in June?
To deal with this question, other studies have looked at high temperatures not in terms of a specific temperature cutoff in numbers of degrees but with respect to what is extreme for a given community. No one in the community would be used to temperatures above the 90th percentile of what is normal for the area. Using this community-specific approach might be more effective and garner more accurate results.
Extreme temperatures early in pregnancyThis approach was used in a recent study by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).
The study looked at temperatures at both ends of the spectrum – greater than the 90th percentile and less than the 10th percentile. It was interesting to note researchers found that both low and high temperatures had an impact on pregnancy outcomes – even though the exposure happened in the first seven weeks of pregnancy.
Why there could be a relationship between weather and early development is difficult to say. It could be something to do with variation in the early development of the placenta growing within the uterus or a change in blood flow to the uterus caused by extreme temperatures.
Clearly, this doesn’t really impact our recommendations to you – we can’t control the weather! – but it’s interesting to know that there might be an effect there.
Recommendations to deal with severe weatherAs we’ve seen, the studies on weather are very inconclusive and probably not clinically significant for any individual patient. Still these ideas persist. There are even websites that track the impact of weather on labor and related health concerns such as mood and aches and pains.
While we can’t come to any hard conclusions, there are some recommendations for dealing with inclement weather that we would want patients to think about.
1. Stay cool in the summer
On hot days, lounging by the pool isn’t bad for you or the baby, and floating in water may actually make you more comfortable because it reduces the heaviness of baby. But avoid high heat and dehydration and apply sunscreen liberally. Overheating and dehydration can be dangerous for both you and the baby, so be sure to take a break inside if you start to feel too hot.
2. Play it safe during inclement weather
If there are ice storms or poor road conditions on the day you are supposed to have an office visit, please go ahead and reschedule your appointment. It is typically not critical you attend an appointment on a specific day, and we would rather have you safe at home.
3. Walk carefully in snow and iceBe very careful when walking outdoors when there is snow or ice on the ground. Your center of gravity is different and could cause you to lose your balance more easily. We see many pregnant patients admitted for observation after falls during periods of inclement weather.
4. Buckle your seat belt properlyIf you are caught driving in inclement weather, make sure your seat belt is on and in the proper position. The lap belt should be below your belly and the shoulder strap positioned between your breasts and over your shoulder.
For more information about pregnancy, labor, and delivery, sign up to receive Your Pregnancy Matters email alerts when we publish new stories. You can also make an appointment to see one of our specialists by calling 214-645-8300.