Pregnancy and Exercise for Athletes: What the Latest Research Actually Says

Pregnancy has long been surrounded by advice, caution, and a lot of fear – especially for athletes. If you’ve ever wondered what you can do, what you shouldn’t worry about, and how pregnancy really affects training, this conversation between researcher Dr. Margie Davenport and pro cyclist Sarah Sturm is packed with answers. In this post, you’ll learn what the evidence says about exercise, resistance training, intensity, hydration, heat, and fueling during pregnancy and postpartum – especially if you’re an athlete trying to stay active without second-guessing every move.

Why Pregnancy and Athlete Advice Has Been So Confusing

For decades, pregnant women were left out of research, and that created a huge gap in guidance. Dr. Margie Davenport explained that until relatively recently, pregnancy was treated more like a reason to avoid data than a reason to collect it.That history matters because a lot of the advice athletes still hear today is based on outdated caution, not current evidence. Things like avoiding heart rate increases, limiting training volume, or steering clear of lifting heavy weights were often built on theory rather than actual studies.Sarah Sturm’s experience captured the emotional side of that gap really well. Like many athletes, she said the first trimester brought fear, uncertainty, and not much reliable information. Even when a doctor says, “If you feel okay, do it,” that’s not always enough when you’re trying to balance performance, health, sponsorships, and the very real fear of miscarriage.The good news is that the research landscape is changing fast. And for athletes, that’s a big deal.

The old “protection by exclusion” model

One of the biggest barriers to pregnancy research was the idea that women should be protected by being excluded. That sounds cautious, but in practice it left pregnant athletes without answers.Dr. Davenport noted that women weren’t removed from clinical research restrictions until 2018. That means a huge amount of the advice people still repeat today is based on absence of evidence, not evidence of harm.

What that meant for athletes

When athletes ask whether they can keep training, they’re often asking questions the research didn’t used to answer. Can you do intervals? Can you lift? Can you race? Can you keep your normal volume? For years, the answer was often “we don’t know,” which made conservative guidance look more confident than it really was.

The Biggest Myths About Exercise During Pregnancy

If there was one big theme in this episode, it was this: a lot of common pregnancy warnings are more fear-based than science-based.

Myth 1: Exercise causes miscarriage

This is one of the most persistent fears, especially in the first trimester. But the data does not support the idea that exercise itself causes miscarriage.Dr. Davenport explained that miscarriage is common – about 15% of pregnancies and roughly 1 in 4 women across a lifetime – but it is usually related to genetic issues, not training. A famous study that seemed to show higher exercise volume increased miscarriage risk turned out to be misleading because it mixed in people who were interviewed after miscarriage, which skewed the results.The key point: exercise does not cause miscarriage. The real caution is under-fueling. If you’re training hard without enough energy intake, that may be where risk increases.

Myth 2: You have to keep your heart rate below an arbitrary cap

Older guidance included a heart rate limit like 140 bpm, but that threshold was never strongly evidence-based. It was more of a conservative rule of thumb than a proven safety boundary.Modern research has moved away from that kind of one-size-fits-all thinking. For many pregnant athletes, it’s less about a single number and more about how the body responds overall.

Myth 3: Heavy lifting is automatically unsafe

This is where the conversation got especially interesting. Dr. Davenport said she originally looked into heavy lifting because someone asked her when they’d need to stop. She couldn’t find any real data – so her team studied it.What they found was striking: among women who were already lifting heavy before pregnancy, continuing to lift was associated with a 50% reduction in pregnancy complications in one survey study. In a follow-up exercise study, heavier lifting was well tolerated in women without exercise contraindications.That doesn’t mean every pregnant person should suddenly start maxing out. But it does mean heavy lifting is not automatically dangerous for everyone.

What the Research Says About Training Intensity and Resistance Work

One of the most important takeaways from the episode is that pregnancy does not mean you need to stop training like an athlete.

Resistance training may be more valuable than people think

Dr. Davenport emphasized that resistance training is one of the most underappreciated forms of exercise during pregnancy and beyond. It matters not just for performance, but for long-term health.Why? Because pregnancy and postpartum can reduce bone mineral density by around 6% on average. That doesn’t automatically mean something is wrong, but it does suggest that the body is under real strain. If you remove bone-loading activities like lifting or plyometrics during a period when bone health already takes a hit, that may not be ideal over the long term.Sarah’s experience matched the research perfectly. She said weightlifting became her anchor during pregnancy – something that helped her feel strong, routine-driven, and mentally grounded. And hearing that it may support pregnancy, childbirth, and postpartum made it easier for her to keep showing up.

HIIT and higher-intensity work may also be okay

The research on high-intensity interval training is still growing, but the early results are encouraging. Dr. Davenport described a study where pregnant athletes did repeated one-minute intervals at very high intensity, with fetal monitoring throughout. Most participants – mom and baby – tolerated it well.That’s a huge shift from the old assumption that intensity itself was the problem.It also helps explain why athletes want better guidance. They’re not looking for permission to do reckless things. They want to know whether the training they already do can continue safely, with adjustments when needed.

Training volume is more nuanced than old limits suggest

Some countries have suggested upper limits like 300 minutes per week during pregnancy, but Dr. Davenport noted that limit is actually lower than what many athletes regularly do.In one study, athletes who trained more than that had about an 88% reduction in pregnancy complications. That doesn’t mean “more is always better,” but it does show how outdated some cap-based recommendations are.The bigger question is not simply how much you move – it’s whether your training is appropriate, well-fueled, and individualized.

How to Fuel and Hydrate Differently During Pregnancy

Exercise is only one part of the story. Pregnancy changes metabolism, blood volume, and hydration needs in ways that matter a lot for athletes.Your caloric needs rise – but not as much as people think. Pregnancy costs about 82,000 calories across nine months, but that increase is not evenly distributed.

• First trimester: calorie needs rise very little
• Second trimester: about 350 additional calories per day
• Third trimester: about 500 additional calories per day

That’s useful context because many people assume pregnancy means eating far more across the board. In reality, the bigger issue for athletes is not just calories – it’s what kind of fuel you’re getting.

Protein and iron become even more important

Protein needs go up during pregnancy, and iron becomes critical because blood volume increases by about 50%. That increase can create what looks like physiological anemia – basically a dilution effect from the extra plasma.For female athletes who may already be borderline low in iron, pregnancy can make that even more important to monitor. If you’re training hard and pregnant, it’s worth being especially intentional about iron-rich foods and any supplementation your clinician recommends.

Hydration needs increase more than many athletes realize

Dr. Davenport said hydration needs rise by about 300 mL per day during pregnancy and about 700 mL per day in postpartum. That might sound small, but if you’re also sweating during training, it adds up fast. She suggested simple checks like urine color – ideally straw-colored, not dark and not completely clear. If you train in heat or humidity, your sweat rate will rise even more, and hydration becomes even more important.Sarah pointed out something many endurance athletes are dealing with right now: heat is hard to avoid. That’s especially true if you’re racing or training in summer, with no air conditioning, or in a region that’s getting hotter every year.

Heat, Core Temperature, and What We Still Don’t Know

Heat is one of the biggest unanswered questions in pregnancy exercise science.

We know pregnancy changes thermoregulation

Pregnant athletes tend to sweat sooner, and the body’s temperature-regulation system changes. The reassuring part is that the limited data we do have suggests most pregnant athletes can still regulate core temperature reasonably well during exercise, even at higher intensities.

But the evidence is still incomplete

The problem is that we do not have enough data in real-world hot conditions. One study looked at exercise in about 32°C heat, which is hot, but not necessarily representative of extreme weather many athletes face.Dr. Davenport also explained that the ideal way to measure core temperature – ingestible sensor pills – are often listed as contraindicated in pregnancy, not because of evidence of harm, but because companies and institutions are cautious without enough data.So the practical advice right now is conservative but not alarmist:

• Avoid unnecessary overheating
• Train in the shade when possible
• Choose cooler times of day
• Prioritize hydration
• Reduce risk when weather conditions are extreme

For pregnant athletes, this is one of the clearest examples of where personalized judgment matters more than blanket rules.

What Happens After Birth – and Why the “Pregnancy Advantage” Matters

One of the most surprising parts of the conversation was the idea that some pregnancy-related cardiovascular changes don’t disappear immediately after delivery.

Your heart adapts during pregnancy

Pregnancy increases blood volume and makes the heart work harder. Over time, those changes can make the heart stronger. Some endurance coaches have even started talking about a “pregnancy advantage” because of these cardiovascular adaptations.Dr. Davenport said those benefits may persist for at least a year postpartum.That doesn’t mean postpartum is a shortcut to fitness or a free performance boost. Recovery still matters, and load management matters even more after birth. But it does suggest that the body retains some useful adaptations far beyond delivery day.

Identity also shifts – and that can help performance

One of the quieter but more powerful parts of the episode was the discussion of identity. Becoming a mom changes how you think, what you care about, and how you use your energy. That can be hard, but it can also help athletes focus more clearly and stop sweating the small stuff.Dr. Davenport shared that parenthood helped her take rejection and setbacks more in stride. Sarah echoed the emotional pressure of trying to stay an athlete while also becoming a parent. That tension is real, and it’s part of why better guidance matters.

The Bottom Line for Pregnant Athletes

The biggest message from this episode is simple: pregnancy is not a reason to stop training by default. The evidence increasingly shows that physical activity, resistance training, and even some higher-intensity exercise can be safe and beneficial during pregnancy for women without contraindications. The most important caveats are fueling, hydration, temperature management, and individualized care.If you’re pregnant and athletic, the goal is not to do nothing. It’s to stay active in a way that respects both your changing body and your sport.That means asking better questions, seeking updated guidance, and avoiding outdated fear-based advice whenever possible. It also means remembering that your experience matters. If you feel good, are fueled well, and have no medical red flags, movement may be one of the best things you can do.

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