August 2019

Pregnancy Changes the Body: Here’s What That Means for Gait, Balance, and Falls

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About a quarter of women fall during pregnancy and 10% fall more than once. Understanding the biomechanical changes of this transitional period may help researchers find ways to prevent such falls.

By Nicole Wetsman

When Robert Catena’s wife was pregnant and working at a restaurant, she fell. It was scary, he says, but everything was ok. One of her co-workers, though, also fell, and wasn’t so lucky: she had severe complications with her pregnancy. Soon after, Catena, a PhD researcher who studies kinesiology and biomechanics, started a new position at Washington State University—and decided to direct his research toward studying balance control in pregnant women.

“Falls are second only to motor vehicles when it comes to injuries caused to pregnant women,” Catena says. About a quarter of women fall during the course of their pregnancies, according to conservative estimates; such falls pose a considerable risk to both the fetus and the pregnant woman. Around 10% of women report falling more than once. The rate is close to the rate of falls in the elderly.1

However, falls aren’t often discussed as risk factors for this population. Pregnancy comes along with a host of physiological changes, but research into the way those changes affect balance, gait, and other biomechanics are limited. Efforts to push the field forward, though, could help reduce fall risk in pregnant women.

How often, where do pregnant women fall?

In a population-based study of 3997 women who had given birth within the past 2 – 7 months, women were asked to report injuries that occurred during the prenatal period, the mechanism and timing of the injury, as well as part(s) of the body injured. Specifically related to falls:

  • 1070 (27%) reported falling at least once
  • Of those 1070
    – 35% reported falling 2 or more times
    – 20% reported seeking medical help
    – 21% had 2 or more days of restricted activity as a result

Where did they fall?

  • 56% fell indoors
  • 36% fell on stairs
  • 9% fell from ≥3 ft (not mutually exclusive)
  • Data from Harland KK et al. Risk factors for maternal injuries in a population-based sample of pregnant women. J Women Health.2014;23(12):1033-1038.

Balance and stability changes

Women undergo a series of physical and hormonal changes during pregnancy, including weight gain around the abdomen, increased joint laxity, due to changes in levels of the hormone relaxin, increased force on joints, and increased pelvic tilt. Among other things, those changes affect the way women stand, walk, and move through the world—and may contribute to changes in their balance, which can increase the likelihood of a fall.

For some time, common wisdom suggested one of the major factors leading to balance and movement changes was the shift forward of a woman’s center of gravity as her stomach and abdomen expanded outward to account for a growing fetus, Catena says. “People believed that was the main contributor to why balance was changing,” he says. But recent research complicated that standard narrative. “We’ve found the center of gravity doesn’t explain as much as we thought.”

In a study published in the Journal of Applied Mechanics in 2019,2 Catena and his team tracked 15 pregnant women starting from around 12 weeks into their pregnancy—performing motion captures, recording anthropometric measurements, and conducting walking balance tests, among other measures, every 4 weeks through the course of gestation. They found that the women’s balance dropped steadily as pregnancy progressed, and that individuals with poor balance prior to pregnancy had the worst balance during pregnancy. However, they found that anthropometric changes to the body and body mass had little relationship with changes and deficits in balance during pregnancy. “We didn’t see a lot of explanations for the variance there. That was interesting,” Catena says.

They found that the women’s balance dropped steadily as pregnancy progressed, and that individuals with poor balance prior to pregnancy had the worst balance during pregnancy

Walking balance decreases over the course of pregnancy, as well, Catena found in a 2018 study published in the journal Gait and Posture.3 His team tested 12 women on a treadmill over the course of pregnancy and classified walking balance and potential for fall as the movement of their center of mass relative to the borders of support on their feet. Walking speed decreased as pregnancy progressed, which corresponded with anterior-posterior motion, as did the women’s ability to stay in the center of the treadmill while walking. Step width increased during the second trimester of pregnancy.

Women have differences in postural stability as they progress through pregnancy, according to a study published in the Journal of Biomechanics in 2010.4 This study compared 81 women, 41 who were pregnant and 40 who were not pregnant. The participants stood on a force plate and their movements and reaction times were measured in response to movement in the plate. There were no differences between pregnant women in their second trimesters and women who were not pregnant; but in the third trimester, pregnant women had less sway in their movements than those who were not pregnant. That finding was contrary to the initial hypothesis, says study author Jean McCrory, PhD, and associate professor in the department of human exercise and physiology at West Virginia University.

“The more advanced they were when we perturbed them, the less movement they had,” she says. “We thought we would see more.” There were a number of reasons for that hypothesis: pregnant women have more of the hormone relaxin, which should make them more lax, and it should take their reflexes longer to kick in. In addition, because they have more mass, the researchers would expect it would take longer to control.

“My theory is that they are adapting to these slower reflexes by co-contracting,” McCrory says. “They’re not normally standing and waiting for something to perturb them. They’re already contracting their muscles, so that they’re much more rigid, and they’re prepared. They might have adapted to having slower reflexes that way.”

In future studies, she plans to use electromyography to measure lower leg muscle response to displacement in pregnant women, in order to determine if they are in fact adapting to slower reflexes in that way.

McCrory was also the first characterize what she calls the “pregnant waddle:” the distinctive side-to-side gait women walk with during pregnancy.5 Kinematic data collected on 29 pregnant women and 40 women who were not pregnant found that women had a wider stance in their third trimester. The data, published in 2014 in the Journal of Biomechanics, also showed that they exhibit more lateral movement during gait.

“We think it’s intuitive to widen your stance when you’re not feeling stable,” McCrory says. “Because you have this massive belly, the body shifts leg to leg rather than bending, because it doesn’t bend so much anymore .”

Increasing fall risk

To identify the characteristics of women who fall during pregnancy, McCrory collected data on a cohort of pregnant women and asked them to report if they did or did not fall. Of the group that remained in the research until it’s conclusion, 15 fell and 14 did not fall during their pregnancy. They were tested twice: once in the second trimester and once in the third trimester. Forty women who were not pregnant served as the control group and were tested once.

One study of this cohort, published in 2014 in the journal Gait and Posture,6 used anthropometric data and data from a motor control test, where subjects were placed in a harness as they stood on a dynamic platform. Pregnant subjects who were fallers had smaller center of pressure–center of gravity values, indicating that they were less able to make corrections in response to shifts in the platform. Pregnant subjects who were non-fallers had more ankle stiffness than those who fell. Increasing ankle stiffness—through exercise or bracing—could therefore be a strategy for reducing falls, the study concluded. Tracking center of pressure–center of gravity values in pregnant women may also serve as a way to identify women at risk of falling.

Another study measured the subjects as they climbed and descended a four-stair staircase, collecting data on their stance, speed, ground reaction forces, and center of pressure. Stance and speed were consistent between pregnant fallers and non-fallers. Pregnant fallers had a larger braking impulse while climbing stairs and a smaller propulsive force when descending stairs, which the study notes might be due to more caution. They also had a larger minimum between vertical peaks during both ascent and descent.7

One of the most interesting data points in the faller and non-faller cohort, McCrory says, is that all of the women who reported that they were sedentary during pregnancy—who didn’t do any exercise—were fallers. Not every woman who exercised was a non-faller, but more than half of exercising women were non-fallers. “I think exercise is really important,” McCrory says. “Maybe it helps you adapt to a changing body. If you’re moving more, you learn how it’s different. If you do encounter a hazardous situation, like water on the floor or a curb, you don’t fall. That was a surprising result. In the small sample, exercise seems to be important.” In some pregnant women, exercise might not be recommended, due to other complications. “As long as it’s not contraindicated, exercise prevents so much, like gestational diabetes and other problems. But it also looks like it really might prevent falls.”

Assessing Fall Risk

Research into the characteristics of pregnant women who both do and do not fall is important to help develop ways to predict which women are at risk of falling, and of ways to counteract that risk.

“Our drive is really to come up with a fall risk assessment of some kind,” Catena says. “How do we differentiate one person from another? Not every pregnant woman is the same, and not everyone will experience the same changes in balance and in walking.”

As well as biomechanical causes, Catena’s team is looking to “attention” as a potential factor in fall risk. “Pregnant women might be focusing attention internally, and not necessarily paying as much attention to the external environment,” he says. They’re also looking into strength and endurance changes. “Anything that might cause the inability to sense how the joints are positioned in the lower extremity.”

Increasing awareness of falls, both for doctors and for pregnant women, is a key element of improving safety.

“I don’t think falls are even on their radar,” McCrory says. “They don’t slip on ice. For the most part, women fall in their homes, or at work. In my study, they only remembered because they had a form to fill out. I think there are more women falling—they just don’t remember, because they don’t get hurt. If they do get hurt, though, it can be disastrous.”

At the moment, many clinicians aren’t talking with their patients about falls. “They tend to be very general, and ask if you’ve experienced a fall, and use that to determine if you’re likely to have another one,” Catena says. “That makes sense, with what we have now. But we don’t want them to experience the first fall.”

Nicole Wetsman is a freelance writer in New York City.

Graduated Compression Stockings Effective in Reducing Varicose Veins in Pregnancy

Figure. Percentage distribution of pregnant women in the intervention and control groups based on the pain (a), edema (b), and heaviness (c) in the lower limbs at the beginning and end of gestation (Botucatu, São Paulo, Brazil, 2017).

This prospective controlled randomized clinical trial was conducted to evaluate the effect of compression stockings in the prevention and control of varicose veins in the lower limbs of pregnant women. Prior studies using ultrasonographic tests had shown that the Great Saphenous Vein (GSV) diameter was higher in pregnant women not using compression stockings than those in the intervention group.

This study population included 60 women who were recruited 10 – 15 weeks into their pregnancy; had a CEAP classification of 0, 1, 2, or 3; and were aged 18-40 years. All were white and had normal pedal or tibial posterior pulses. Clinical evaluations and Duplex-ultrasound were performed by 2 qualified examiners in 120 lower limbs of the 60 pregnant women in 2 periods: between the 10th and 13th and between the 30th and 33rd week of gestation. The study protocol included examination of the deep and superficial venous system; the GSV and SSV in the thighs and legs were mapped and analyzed.

Women in the intervention group (n=30) received 3 pairs of compression stockings (20-30 mmHg; BASIC style, Sigvaris Inc., Peachtree City, GA) and were told to wear them for 8 hours/day. The stockings were correct for ankle and calf diameters and height of the leg (measured from the calcaneus to the knee). Biweekly telephone calls were used to monitor regular use of the stockings. Women in the control group were treated with standard of care.

Results: Great saphenous vein diameters in the intervention group were 0.37 cm initial and 0.32 cm final (p<0.0001) in the right leg and 0.28 cm and 0.38 cm (p<0.0001) in the control group. CEAP classification presented worsening in the control group (p<0.0001). The signs and symptoms reported in the control vs. intervention groups: pain (86.67% vs. 23.33%; p<0.0001), edema (70.00% vs. 33.33%; p=0.0045), and leg heaviness (93.33% vs. 13.33%; p<0.0001).

Worsening of the CEAP classification in the control group included progression to CEAP classes 4 and 6, with significant changes in skin and one active ulcer. Women in the intervention group appeared to remain stable until the end. Pain in the lower limbs, the most common symptom of varicose veins, was also highly prevalent in the control group, yet was least prevalent in the intervention group. Furthermore, the reduced prevalence of all symptoms in the intervention group is indicative of the effectiveness of the therapy.

The authors noted that all women in the intervention group reported that they felt an improvement of symptoms in the legs and that they would use the compression stockings again. These findings mirror those of others who observed that acceptance of the stockings was associated with regular use, and regular use was associated with patients’ improved quality of life.

In this study, the prescribed compression stocking had a compression of 20–30 mmHg, and reflux at the end of the research were noted in 0/30 patients in the intervention group and 16/30 patients in the control group, findings similar to Thaler et al and to Uhl’s study using computed tomography. The reduction of venous diameters suggests that this therapeutic protocol was effective in the control of varicose veins and the relief of undesirable signs and symptoms of edema, pain, and heaviness in the lower limbs which occur frequently during pregnancy.

In conclusion, the authors noted that patients who used the compression stockings had reduced GSV and SSV diameters, improved signs and symptoms of venous insufficiency in the lower limbs, and were highly satisfied with the use of compression stockings.

Source: Saliba Junior OA, Rollo HA, Saliba O, Sobreira ML. Graduated compression stockings effects on chronic venous disease signs and symptoms during pregnancy. Phlebology. 2019; May 1:268355519846740. [Online First]

REFERENCES
  1. Dunning K, LeMasters G, Bhattacharya A. A major public health issue: the high incidence of falls during pregnancy. Matern Child Health J. 2010;14(5):720-725.
  2. Catena RD, Campbell N, Werner AL, Iverson KM. Anthropometric Changes During Pregnancy Provide Little Explanation of Dynamic Balance Changes. J Appl Biomech. 2019;35(3):232-239.
  3. Flores D, Connolly CP, Campbell N, Catena RD. Walking balance on a treadmill changes during pregnancy. Gait Posture. 2018;66:146-150.
  4. McCrory JL, Chambers AJ, Daftary A, Redfern MS. Dynamic postural stability during advancing pregnancy. J Biomech. 2010;43(12):2434-2439.
  5. McCrory JL, Chambers AJ, Daftary A, Redfern MS. The pregnant “waddle”: an evaluation of torso kinematics in pregnancy. J Biomech. 2014;47(12):2964-2968.
  6. Ersal T, McCrory JL, Sienko KH. Theoretical and experimental indicators of falls during pregnancy as assessed by postural perturbations. Gait Posture. 2014;39(1):218-223.
  7. McCrory JL, Chambers AJ, Daftary A, Redfern MS. Ground reaction forces during gait in pregnant fallers and non-fallers. Gait Posture. 2011;34(4):524-528.

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