Pregnancy Weightlifting | The studies that prompted the 10-pound rule

When Rosalie Watson found out she was pregnant, she was shocked.

“My first reaction,” she said, “was ‘but I was off to such a good year with my lifting and was supposed to be doing nationals, now what?!'”

Having lifted for 10 years and competed as a power lifter for five years, Watson told her doctors she planned to continue training. They were skeptical.

Then she received this letter:

Doctor Letter

Dear Rosalie,

I just reviewed the recommendations around heavy lifting in pregnancy. There is not much evidence around, but doing heavy lifting may increase your risk of miscarriage and hence the repetitive heavy lifting during the first trimester is mentioned as something to be avoided. There is not much evidence, to be honest, but they talk about heavy lifting being more than 20 kg [44 pounds] more than 20 times a week.

That weekend, Watson competed in a powerlifting competition, squatting 275 pounds, benching 176 pounds, and deadlifting 330 pounds.

“I was at first a little iffy about my lifting as there’s so much ill advice out there,” Watson said in a post on social media. “Apart from feeling more tired than usual leading up to [the competition], my body was well conditioned to do those lifts. I don’t know what each step of pregnancy will feel like but I’ll do what I can throughout.”

Now 15 weeks along, Watson is still lifting and training for a competition in November, although she said it’s just for fun.

“I’m still lifting because it’s my passion and my hobby, plus my job,” she said. “If I’m not lifting, I would be one unhappy person.  … Also I believe (and hopefully it’s true) that my birth will be more straight forward for being strong. The power of lifting heavy has such a positive effect not only physically but mentally, it makes me feel like I can do almost anything.”

The studies Watson’s doctor references are peer-reviewed scientific studies published in academic journals. However, they have little to do with the sport of weightlifting.

Here, we take a look at the studies that prompted the limitations on lifting in pregnancy, along with other medical studies surrounding exercise in pregnancy.

The original study

In the early 1980s, Swedish researchers followed nearly 4,000 pregnant women whose work required them to lift loads in excess of 12 kg (25 pounds). Their study aimed to discover whether lifting heavy loads multiple times per week contributed to pre-term birth, miscarriage, or still birth.

Over the course of the three-year study, researchers concluded that occupational lifting performed more than 50 times per week contributed to pre-term birth; but did not increase a woman’s chances of miscarriage or still birth.

After publishing in 1990, the study led Sweden and other countries to regulate occupational lifting requirements for pregnant women. The Danish National Birth Cohort bolstered this by completing a similar study from 1996-2002 and coming to the same conclusions.

As a result, doctors worldwide use these findings as a blanket recommendation to women not to lift more than 25 pounds. Ever. For any reason.

The problem with this? It isn’t relevant to weightlifting and it isn’t practical — ask any expecting mom with a toddler.

The study follows women lifting in an occupational setting. It isn’t clear whether these women received any training on how to properly lift or whether they were lifting those loads prior to getting pregnant.

But medical professionals still err on the side of caution.

“When a doctor says not to lift more than 10 or 20 pounds, they may as well say not to lift anything,” says Catherine Cram, fitness instructor and co-author of “Exercising Through Your Pregnancy.”

Cram says there are precautions women should take in pregnancy, but that applies to all activities, not just weightlifting.

The 140-BPM rule

About the same time the Swedes published their study in the early 1990s, researchers for the Medicine and Science in Sports and Exercise journal concluded that pregnant women who exercised experienced similar weight gain, infant birth weight, length of gestation, length of labor and Apgar scores as women who remained sedentary.

The kicker? These women did not exceed a heart rate of more than 144 beats per minute, moderate exercise for most women.

The study concluded, “Overall, an exercise program using any of a variety of exercise modes that is performed for an average of 43 min, 3 times per week, at a heart rate of up to 144 bpm, does not appear to be associated with adverse effects to the mother or fetus in a healthy normal pregnancy.

“However,” researchers cautioned, “these findings should be cautiously applied owing to the nature of the currently available data base. ”

The problem with this study: women used to a rigorous workout program (read: CrossFit or weightlifting) typically exceed the 140-bpm threshold.

Nearly two decades later, researchers from Norway reassessed the 140-rule. They followed six Olympic athletes through their pregnancies, measuring fetal heart rates in relation to maternal heart rate as well as uterine artery volume blood flow.

Their study concluded, “Exercise at intensity above 90 percent of maximal MHR in pregnant elite athletes may compromise fetal wellbeing.”

Although this is good news for women hoping to continue their workout regimens in pregnancy, medical professionals are shifting away from using heart rate as a measure for strenuous workouts. Instead, doctors are encouraging women to assess how they feel during and after workouts.

The doctor who started a revolution

When Dr. Raul Artal worked with high-risk patients in the early 1980s, he saw numerous patients struggling with obesity and diabetes.

“The recommendation for these patients at the time was bed rest,” he said. “But that just didn’t make sense to me to further confine these women and restrict activity.”

Artal became the first physician to introduce guidelines for exercise and physical activity for the American Congress of Obstetricians and Gynecologists in 1982. He faced opposition at every turn.

Scientific studies surrounding pregnant exercise cautioned overexertion. Doctors hesitated to recommend exercise to patients.

In a 2016 interview with the Washington Post, Artal stated, “Initially, we approached the guidelines with much caution. … Over the years, it progressed to where we said, ‘It’s OK to exercise in pregnancy.’ It was not until this past year that we said, ‘It’s also OK to engage in vigorous, intensive exercise, provided there are no complications of pregnancy.”

Now a retired medical doctor working as a professor and chair emeritus for the Department of Obstetrics/Gynecology and Women’s Health at Saint Louis University, Artal still makes recommendations for exercise and physical activity for ACOG, but he no longer faces the disdain he once did.

“It has been an uphill struggle,” he said. “But we eventually liberated these women.”

Generation Fit Pregnancy

Over the past 10 years, the number of women participating in “elite” sports such as CrossFit and weightlifting skyrocketed.

In 2007, membership to USA Weightlifting was less than 4,500 with fewer than 20 percent women. In 2017, there are more than 26,000 USAW members and women make up more than a third of that population.

Nearly 300,000 athletes participated the 2017 CrossFit Games Open, and nearly half were women.

Why is this relevant?

More and more women are participating in these high levels of sport. It is logical that a percentage of these women will become pregnant and may want to continue pursuing the training regimen they have already worked so hard for.

In 1987, the American Journal of Obstetrics and Gynecology published findings that women who exercised experienced shorter hospital stays and fewer cesarian sections, and their babies had higher Apgar scores. This was particularly true of women in the “high exercise” group.

Before his death in 2015, Dr. James F. Clapp III, OB/GYN and co-author of “Exercising Through Your Pregnancy,” participated in numerous studies that highlighted the benefits of exercise for both mom and baby.

One study, published in 2011, explored strength training in pregnancy. It concluded that a “low-to-moderate intensity strength training program during pregnancy can be safe and efficacious for pregnant women.”

The tides are shifting to support exercise during pregnancy. Heck, even the U.S. military updated its recommendations for pregnant service members.

In the September 2016 Clinical Obstetrics and Gynecology issue, researchers published numerous studies related to exercise in pregnancy, including a study titled, “The Elite Athlete and Strenuous Exercise in Pregnancy.”

“One of the challenges with writing about the effects of strenuous activity on elite athletes during pregnancy is definitional,” the authors wrote. “Specifically, what constitutes an ‘elite athlete’ and what is meant by ‘strenuous exercise’?”

For this study, researchers settled on defining “elite athlete” as someone who trains at least five days per week, averaging close to two hours per day. Researchers used a metabolic equivalent of 6.0 or above to define “strenuous activity.”

Metabolic Equivalent

According to some websites, sleep has an MET rating of .9 while exercises requiring heavy, vigorous effort or pushing or pulling with one’s entire strength rank at an 8.0. Interestingly, sexual activity ranks at a 5.8, almost the threshold of “strenuous activity.”

The study concluded that women who met these criteria throughout their pregnancies had reduced risks of preeclampsia, possibly because they had lower pre-pregnancy blood pressure; were less likely to be overweight and obese; and less likely to have pre-diabetes, all of which contribute to preeclampsia risk.

In the same issue of the Clinical Obstetrics and Gynecology journal, researchers published “Resistance Training in Pregnancy and Outcome,” which collected previous exercise studies that involved aerobic, resistance, or strengthening programs. Researchers then compared gestational age, type of delivery, maternal weight gain, birthweight, birth length, and Apgar scores to determine if one type of exercise was more beneficial or detrimental than another.

“The greatest difficulty we found was the small number of  studies  investigating  resistance  or strengthening programs on pregnancy outcomes in comparison with aerobic exercise,” researchers wrote. “Possibly the traditional advice for pregnant women to rest may be responsible for this low number of studies. However, no adverse results pertaining to maternal and fetal/newborn well-being were found in the analyzed studies with resistance or strengthening interventions.”

Despite the limited studies focusing on strength training, specifically heavy lifting, the American Congress for Obstetricians and Gynecologists deemed strength training safe in 2015.

With so many women entering into the realm of “elite” fitness, the scientific community needs more research to provide relevant safety guidelines for pregnancy. But doctors such as Artal say if you have no complications, go for it.

“If the patient has no contraindications or relative indications, they can do almost anything they wish,” Artal said. “Pregnancy is not a state of confinement.”

Want more? Read part three of our series: When to push, scale, and modify.

In case you missed it: part one of our series: Five reasons to exercise during pregnancy.

Disclaimer: Andrea Signor is a writer. She does not have any medical background or fitness certifications. She is a former journalist with an interest in weightlifting. Any woman interested in exercising and lifting in her pregnancy should consult with her medical team and fitness coaches.

14 Replies to “Pregnancy Weightlifting | The studies that prompted the 10-pound rule”

  1. Though I never weight lifted (ever), I ran and did yoga during both of my pregnancies. I had my first daughter at 36 weeks but was more active (running) with my second daughter and had her at 38 weeks. I’m so happy I was active during my pregnancies and would do it all again!

    1. That is so awesome, Anna! I’m in awe of women who can run right up to the end of their pregnancies. I feel like weightlifting is so much easier! Lol. 🙂

  2. I did my best to remain as active as I could during my pregnancy, which included doing light weight training. All of my activities were approved by my OB. Being open and candid with your doctor is most important, as they will be able to guide you on what is/isn’t safe for you and the baby based on your history, etc.

    1. Definitely agree, Kathryn. It does concern me when I hear that women are withholding their training from their docs for fear of being ridiculed or admonished. Everyone wants the best outcome for mother and baby.

  3. It is so crazy how the information has changed so much over the years. I have always been a weight lifter and I did train through my pregnancy. I trained at a level I knew I was comfortable with and listened to my body, it was a great experience!

    1. Yes, Stephanie! I was overly cautious (but still lifted relatively heavy) in my first pregnancy. My pregnancy, labor, and delivery were textbook; but my recovery took a lot longer than I anticipated. I lifted heavier in my second pregnancy and my recovery was lightyears faster. Hard to know if it was because I was working out more or because it was my second go-around and I knew what to expect (probably a bit of both), but I would take the second time any day!

  4. I would think (like with most anything else pregnancy-related), common sense would prevail. If the gal is already knowledgeable about weight-training, she would know what is “too much” and what isn’t. The pregnant gal’s center of gravity would be compromised in the later months, so it would be critical to pay particular attention to form…but, again, with the guidance of a trainer (and her own common sense), it would be a great way to maintain muscle tone and stay active.

    1. Agreed. Toddlers weigh more than 10 pounds so to suggest that a woman shouldn’t lift her 2- or 3-year-old for nine months is completely unrealistic (unless there’s a medical reason she shouldn’t). I love that docs are giving power back to the moms.

  5. It’s so amazing how much misinformation is out there, and the unfortunate thing is you might find old, outdated recommendations when better and more researched information is out there. In the end, I think it’s best to know yourself and do what is best for YOU.

  6. I consider myself lucky. My ob for my second born (when I had been running for three years by then) was extremely supportive of me. She told me to listen to my body because only my body knows what it can/cannot do. So I did. And I ran (happily) until the day before I delivered my daughter.

  7. I ran during my pregnancy and probably had a heart rate exceeding 140 bpm because I know my natural tendancy is to run at a pace that produces a heart rate of ~163 bpm, and I had two other children at home (5 & 3) that hated walking. That baby is now almost 7 and is fine. She was born a week early after a 67 minute labour. I think it’s time they do some real studies with real women who exercise on a regular basis 🙂

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