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Does Running While Pregnant Shake the Baby?

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Does Running While Pregnant Shake the Baby?

No, running while pregnant does not shake your baby in any harmful way. Your baby floats in amniotic fluid inside the amniotic sac, and that fluid cushions them from your movements, including the up-and-down bounce of running. The muscular wall of your uterus and your abdominal muscles add more layers of protection.

If your pregnancy is uncomplicated and you ran regularly before you got pregnant, it is usually safe to keep running for as long as it feels comfortable. The things that deserve your attention have nothing to do with bouncing. They are falls, overheating, all-out efforts, pelvic floor symptoms, and a short list of warning signs.

Pregnant woman jogging on a park path

Why running doesn’t cause shaken baby syndrome

Shaken baby syndrome, also called abusive head trauma, is a serious brain injury caused by forcefully shaking an infant or toddler. Babies have weak neck muscles and can’t support the weight of their heads. When a baby is shaken forcefully, the brain moves back and forth inside the skull, which causes bruising, swelling and bleeding.

Running doesn’t create those conditions. Before birth, your baby’s head isn’t whipping back and forth on an unsupported neck. Your baby is surrounded on every side by fluid. Even after birth, Mayo Clinic states that shaken baby syndrome is not caused by bouncing a child on your knee.

The research points the same way. The systematic reviews behind Canada’s pregnancy exercise guideline found moderate benefits from physical activity during pregnancy and identified no harms.

Does it matter which trimester you’re in?

Your baby is protected in every trimester. What changes as your pregnancy progresses is where your uterus sits, how exposed your belly is to a fall, and how running feels for you.

First trimester

For roughly the first 12 weeks, your uterus sits low inside your bony pelvis, which protects it from outside impact. Canada’s guideline recognizes that tiredness and the discomforts of pregnancy can make it hard to stay active at times, and it encourages you to do what you can.

Second trimester

After about 12 weeks, the uterus rises out of the pelvis and grows up into the abdomen. Your baby is still cushioned by fluid, but your belly is now more exposed to a direct blow. That is why falls matter more from this point on.

Third trimester

Your baby is still well cushioned late in pregnancy. The amount of amniotic fluid peaks in the mid-30s weeks, at a little less than 1 litre, and then slowly decreases toward your due date. The bigger change is you: as your bump grows, your centre of gravity shifts and affects your balance, and your pace will probably slow down naturally.

What happens to your baby when you run

When you run, your baby’s heart rate usually rises a little. A 2019 systematic review of 91 studies, covering 4,641 pregnant women, found that fetal heart rate went up by about 6 beats per minute on average during exercise and about 4 beats per minute afterward. Slow fetal heart rate was rare at rest and didn’t become more common with exercise. Blood flow in the umbilical cord and uterus didn’t change significantly. The quality of the evidence ranged from very low to moderate, but the reviewers concluded that exercise during pregnancy does not harm the baby’s heart rate or the blood flow to the placenta.

Studies of birth outcomes are reassuring too. A large international study looked back at the pregnancies of 1,293 women recruited through parkrun, the weekly 5 km running events. Continuing to run did not affect how many weeks along babies were born or their birthweight, no matter how far the women ran each week or how late in pregnancy they kept running. Because the study looked back at past pregnancies, it can’t prove cause and effect, but its findings match the wider research.

Canada’s national guideline reaches the same conclusion. Physical activity during pregnancy is not associated with miscarriage, stillbirth, preterm birth, low birth weight or birth defects. Being active also lowers the risk of several pregnancy complications, which you can read more about in our guide to the benefits of working out during pregnancy.

Is there a week when you have to stop running?

No, there is no set week when you have to stop running. Canada’s guideline says people who were active before pregnancy can continue throughout pregnancy. If you ran regularly before becoming pregnant, it is usually safe to keep going for as long as it feels comfortable. Some people run right up until their due date, while others switch to walking or swimming later in pregnancy because it feels better.

You should stop if your doctor or midwife advises it, or if you notice any of the warning signs listed further down this page.

How far and how hard can you run while pregnant?

There is no official distance limit for running during pregnancy, and you don’t need to keep your pre-pregnancy pace or distance. The 2019 Canadian guideline recommends at least 150 minutes of moderate-intensity activity per week, spread over at least three days. The guideline authors also note that there isn’t enough evidence to say whether exercising far above that level is safe or adds extra benefit.

Can you run a 10K or a half marathon while pregnant?

Possibly, if you were already running those distances before pregnancy, your pregnancy is uncomplicated, and your doctor or midwife agrees. Pregnancy is not the time to train for your first long race.

Can you run a marathon or race competitively while pregnant?

Some people can continue competitive running once their doctor or midwife has confirmed it is safe. If this is your plan, ask to see an obstetrician who specializes in pregnancy and sport, and avoid pushing yourself too hard.

Use the talk test

You’re at a comfortable intensity if you can keep up a conversation while you run. If you can’t talk, slow down.

Avoid all-out efforts

A small Norwegian study tested six Olympic-level endurance athletes between 23 and 29 weeks of pregnancy on a treadmill. Their babies’ heart rates stayed normal as long as the women ran below 90% of their maximum heart rate. When two of the women went above that level, blood flow to the uterus dropped sharply and their babies’ heart rates slowed. The heart rates recovered quickly once they stopped. This study involved elite athletes running near their limit, not recreational runners jogging at a conversational pace. It is still a good reason to skip race-pace efforts and maximal intervals until after your baby is born.

If you’ve never run before

Pregnancy is not the time to start running. That doesn’t mean sitting still. Canada’s guideline recommends that everyone without a medical reason to avoid exercise stays active during pregnancy, building up gradually. Brisk walking, swimming, a stationary bike or a prenatal yoga class are good places to start. Our article on how many steps to walk a day while pregnant can help you set a starting point.

The real risks: falls and overheating

Falls

A fall is the main way running could put your baby at risk, because it can cause a direct blow to your belly. Canada’s guideline advises avoiding activities with physical contact or a danger of falling. To lower your risk:

  • Run on even ground. Stick to paths instead of rough trails, or use a running track or treadmill.
  • Watch your footing more than usual as your bump grows and your balance changes.
  • In a Toronto winter, move indoors when sidewalks are icy.
  • Wear supportive running shoes and a proper running bra.

Falls later in pregnancy can be more harmful, especially if you land on your belly. A fall like that can cause contractions, leaking of amniotic fluid, or placental abruption (the placenta separating from the wall of the uterus). If you fall after about 23 weeks, contact your doctor or midwife right away. If you fall earlier in pregnancy, still tell your doctor or midwife and describe any symptoms. Get checked right away if you have bleeding, fluid leaking from your vagina, contractions, or pain or tenderness around your uterus.

Overheating

Canada’s guideline advises avoiding exercise in excessive heat, especially when it’s humid. Don’t start a run on a very hot day. Run early in the morning or in the evening, pick shaded routes, or run indoors. Staying hydrated during pregnancy matters even more when you exercise, so drink plenty of water.

Pelvic pressure, leaking or heaviness while running

Running places extra demands on your pelvic floor, the group of muscles that supports your bladder, bowel and uterus. Keeping these muscles strong during pregnancy may help prevent pelvic floor problems later. Canada’s guideline says daily pelvic floor exercises (Kegels) can lower the risk of leaking urine, and that learning the right technique helps you get the full benefit.

Leaking urine when you exercise, or a heavy feeling in your vagina or a feeling that something is coming down, are signs of a pelvic floor problem. A pelvic health physiotherapist can help. If running causes pain, stop or cut back. If you have a deep pain in your belly or pelvis, don’t exercise, and talk to your doctor or midwife. Our partner The Mom Loft offers pelvic floor therapy in Toronto.

When to check with your doctor or midwife before running

Most people can stay active throughout pregnancy. But Canada’s guideline lists conditions where strenuous exercise, including running, isn’t recommended. People with these conditions can usually keep up normal daily activities:

  • ruptured membranes (your water has broken) or premature labour
  • unexplained vaginal bleeding that keeps happening
  • placenta previa after 28 weeks
  • preeclampsia
  • an incompetent cervix (a cervix that opens too early)
  • intrauterine growth restriction (the baby isn’t growing as expected)
  • triplets or more
  • uncontrolled type 1 diabetes, high blood pressure or thyroid disease
  • another serious heart, lung or whole-body condition

For some other conditions, you should talk through the pros and cons of moderate-to-vigorous exercise with your doctor or midwife first. These include repeated pregnancy loss, high blood pressure that started in pregnancy, a previous spontaneous preterm birth, mild or moderate heart or lung disease, anemia with symptoms, malnutrition, an eating disorder, or a twin pregnancy after 28 weeks.

Stop running and get medical advice if you notice these signs

Stop right away and contact your doctor or midwife if you notice any of these during or after a run:

  • trouble catching your breath, or shortness of breath that doesn’t go away with rest
  • chest pain
  • a very fast or irregular heartbeat
  • regular, painful contractions or tightenings in your belly (see how to tell real contractions from Braxton Hicks)
  • vaginal bleeding
  • fluid leaking from your vagina
  • dizziness or feeling faint
  • pain in your belly or a deep pain in your pelvis
  • a bad headache
  • muscle weakness that makes you lose your balance
  • pain or swelling in your lower leg
  • your baby moving less than usual (learn more about your baby’s movements and kicks)

These symptoms can be a sign of early labour or a pregnancy complication. If your baby is moving less than usual, contact your hospital’s labour and delivery unit immediately and don’t wait. For any of these symptoms, call your doctor or midwife or go to hospital. An elective ultrasound studio is not the right place to check symptoms.

See your baby moving for yourself

On an ultrasound, the pockets of amniotic fluid around your baby show up as dark areas. That fluid is the same cushion that protects your baby on every run. Many parents enjoy watching their baby turning, stretching and kicking inside it.

At A Date With Baby in Toronto, our Reassurance Scan is available from 15 weeks until your due date. You watch your baby’s activity live and see and hear the heartbeat. An elective scan is not a medical check-up, and it doesn’t replace the ultrasounds and prenatal care from your doctor or midwife. If you’re wondering about safety, read how many ultrasounds during pregnancy are safe.

Sources

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