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Pregnancy: Peer-Reviewed Studies

During pregnancy, the ligaments, under hormonal influences, become lax and stretch to allow the pelvis to spread for delivery. To balance this, the counternutation muscles are automatically tightened, and the nutation muscles are relaxed. With this imbalance in muscle activation patterns, both sets of muscles don’t pump properly so they have reduced circulation. The resulting decrease in nutrition to the cells and build-up of cellular waste is the source of most muscular pain. The importance of implementing a sacroiliac belt during pregnancy cannot be overemphasized; it keeps the sacroiliac joint within normal range of motion, restores muscular balance, and reduces pain.

There is a time, near the beginning of labor that the mother must switch, from activating the counternutation muscles, which support the baby, to activating the nutation muscles to push the baby out. At this time use of a sacroiliac belt should be discontinued until after delivery. During labor, the hips are flexed, bringing the thighs close to the pelvis. Pulled by the hamstrings, the pelvis is rotated posteriorly into nutation. The sacral base rotates anteriorly. The ischial tuberosities separate, and the pelvic outlet opens for delivery. Delivery is a process involving nutation to the extreme.

After delivery it is important to hold the sacroiliac (SIJ) and pubic joints firmly together in order to assist the ligaments in shortening and realigning the pelvis properly. There is a misconception that supporting the belly muscles will help shrink the hips when, in reality, you can’t push a muscle into shape. Instead, an appropriate SI belt, such as the Serola Sacroiliac Belt, achieves this and much more. By acting as an external ligament, the first, non-elastic layer keeps the pelvis from widening, while the second, elastic layer, compresses and shrinks the pelvis. Then, tightening the non-elastic layer helps maintain the gains made, in a continuous cycle of reducing pelvic dimensions back toward pre-pregnancy sizing.

In 1957, Borell and Fernstrom[1] described “the movements at the sacroiliac joint are of importance to the descent of the head through the pelvic canal. These movements cause upward and downward displacement of the symphysis pubis as well as changes in the true conjugate diameter of the outlet.”

In a study of 17 autopsied females, examined 24-48 hours after death, the average motion of the SIJ was 4 degrees. Of these, the maximum motion was 8 degrees, twice the average, in a woman who had a full-term delivery shortly before her death. This offers some evidence of the laxity present in pregnant women. It is reasonable that this laxity can lead to displacement if not properly aligned and supported post-pregnancy.

Ostgaard, H. C., et al. [2] did a study which analyzed an education and training program concerning back and pelvic problems among pregnant women. 407 consecutive pregnant women were included in the study. Weekly physical exercise before pregnancy reduced the risk for back pain problems in pregnancy (P < 0.05). A non-elastic sacroiliac belt offered some pain relief to 82% of the women with posterior pelvic pain.

In a study of 862 women during pregnancy, Berg et al. [3] found that “49% experienced backache and one-third of these women considered the backache severe…The most common reason for severe low back pain (LBP) was dysfunction of the sacroiliac joints…and 79 women developed such severe pain that they were unable to continue work… Of these 79 women with severe pain, 72% experienced relief with a trochanteric (sacroiliac) belt.”

Fast et al. [4] referred to a similar observation by Berg et al. [3] who interviewed 862 women in a Swedish clinic, and also noted that “Dysfunction of the sacroiliac joint was found in two-thirds of the women with severe back pain. This is important because dysfunction of the sacroiliac joints should be treated differently from other causes of LBP…Backache tended to remain a problem after delivery among two-thirds of the women with severe pain during pregnancy. In some women, the pain persisted at least a year after the delivery. Most women treated with the trochanteric belt reported good results.” A trochanteric belt is the same as a sacroiliac belt, but it refers to being worn in the lower position.

Nilsson-Wikmar et al. [5] divided 118 pregnant women into three groups, one with only a pelvic belt and an informational brochure on their condition with no exercise program. The other two groups were given different types of exercise programs, in addition to the belt and brochure. All women were tested at week 38 of pregnancy and 3, 6, and 12 weeks postpartum. They state that “At the three-month follow-up, 57% in group 1 and 35% in group 2 and 3 were pain free…In conclusion, pelvic pain diagnosed during pregnancy seems to improve with time in all three different treatment groups.” However, it should be noted that the group with only the belt and informational brochure benefited the most.

Mens et al.[6] found that, “Reassurance of patient and awaiting spontaneous resolution, in combination with instructions and use of a pelvic belt, are, with the present knowledge, our first choice for managing this condition.“

Foley et al. [7] stated: “A sacroiliac joint belt can be fitted to provide stability and reduce pain. This is a particularly good option for pregnancy-induced SIJ dysfunction, given the increased mobility and given that the use of medicines, fluoroscopy, and injections must be limited”.

In a study of 262 women with pelvic pain, Mens et al. [8] gave 147 women a pelvic belt. He stated “After childbirth 147 patients used a pelvic belt. Of these patients, 10% reported more pain, 23% had no effect, and 67% a positive effect.” They suggested that, “The influence of physical activities on pelvic pain and the relief with the use of a pelvic belt in about 60% of the patients implicates the locomotor system as a cause for pelvic pain, and not an inner organ such as the uterus.”

In a study of 407 pregnant women, Ostgaard et al.[9] demonstrated a reduction of posterior pelvic pain in 82% of the women with use of a non-elastic SI belt, especially while walking. They stated that “The use of a low non-elastic sacroiliac belt was a cost effective unharmful tool for pain relief in many women with posterior pelvic pain.” Because no side effects were found, they recommended the use of non-elastic sacroiliac belts for pregnant women who experienced posterior pelvic pain.

Hansen [10] states that “In Norway, approximately 37% of pregnant women seem to suffer from low-back pain and/or sacroiliac and pubic pain during pregnancy. Most of them seem to recover after delivery, but some still have their problems, and some of them even get worse after delivery…Pain is most often localized to the lumbar sacral area, and just as often to the pubic symphysis.”

In another study, Fast et al. [11] interviewed 200 women within 24-36 hours after delivery. “It was found that 56% of the patients suffered from low-back pain during pregnancy” … and most of the pain occurred during months 5-7, although it commonly occurred after the second month up to delivery. The pain “radiated in 45.5% of cases to the lower extremities.” “Several activities tended to increase the pain. As expected, the most common ones were standing, sitting, forward bending, lifting, and walking. Coughing, sneezing, and straining during bowel movement increased the pain in 30% of patients…Of great interest is the night pain complained of by 35.7% of patients…Those patients render the concept of fatigue stress untenable as a sole cause.” Bending, lifting, and twisting are the three most injurious activities to the SIJ. Coughing, sneezing, and straining during bowel movement all create strong nutation movements and can easily aggravate the nutation lesion. Walking causes sheer stress on the SIJ as the weight shifts during single leg stance, especially when the restraining ligaments are weak and strained. Sleeping in various positions can aggravate the SI lesion – see Dr. Serola’s Do’s and Don’ts.

Fast et al. [4] referring to Mantle et al. [12] also stated that “Women with low back pain in previous pregnancies had a 3-fold increased risk of developing sacroiliac joint dysfunction compared with those who had no pain in previous pregnancies.”

Mantle et al. [12] stated that “Replies to a questionnaire showed that, amongst 180 women delivered in The London Hospital, 48% experienced backache during pregnancy; in one third of these it was severe.”

Wu et al. [13] found that 45% of all pregnant women and 25% of all women post-partum suffer from pregnancy related low back or pelvic pain. During pregnancy, 45% have some pain, 25% develop serious pain, and 8% develop severe disability. After pregnancy, serious problems remain in 7% of women.

Mens et al. [14, 15] work in a clinic in Rotterdam where they, almost exclusively treat pregnant and post-pregnant women. From their years of work and research, they state that the first episode of women with chronic (LBP) occurred during pregnancy in 10-28% of their patients.

Further, Mens et al. [8] found that of 217 women who previously had pelvic pain during pregnancy, 85% had a recurrence of pelvic pain.

In a study of 449 pregnant women, Orvieto et al. [16] found that “246 (54.8%) women reported LBP in the present pregnancy. Factors which were found to be significantly associated with an increased risk to develop LBP during pregnancy included low socioeconomic class, existence of LBP before the first pregnancy, during previous pregnancy, and interim pregnancies.”

In a study of 394 women with pain related to pregnancy, Mens et al. [8] found “the sites where the pain is experienced: mostly in the symphysis region (77%) and the groins (53 and 52%). Pain in the midline at the level of the sacrum is reported by 29%, the coccyx 33% and the dorsal upper iliac spines (posterior superior iliac spines) 41 and 42%.” Further “For 60% of the women the pain began during the first pregnancy…it began during the first three months for 21% and…34% state that the complaints began during childbirth or during the subsequent three weeks…Here the percentage of first pregnancies is even higher (82%).” “The risk of relapse with a new pregnancy is high…About 85% again experienced pelvic pain.”

Further, in summarizing a number of studies, such as those above, Fast et al. [4] stated “it seems that about 10% of pregnant women are prone to develop severe LBP that will interfere with their quality of life during pregnancy and may linger on after delivery.”

Similar to pregnancy, menstruation may make SIJ stabilization more difficult to acquire and maintain. DonTigny [17] states “The presence of relaxin in the body about a week or 10 days before the onset of menstruation effects a hormonal ligamentous laxity similar to that of pregnancy but to a lesser degree and renders the pelvic ligaments less stable and, this, more prone to minor injury. The relaxin is reabsorbed during menstruation and if the innominate is kept in its normal position on the sacrum at this time, the pelvic ligaments seem to regain their normal stability. I have observed that if the dysfunction is not corrected, the instability may continue into the next menstrual cycle.” It would seem appropriate then, since a proper SI belt can help stabilize the sacroiliac joint, its use during menstruation would be beneficial.

Calguneri et al. [18] stated that relaxin increases during menstruation and correlates with increased mobility of the sacroiliac joints. During pregnancy, relaxin increases up to 10-fold, peaking around 38-42 weeks.

Scholten et al. [19] found that decreasing pubic symphysis stiffness significantly increased iliac movement at the SIJ. So, it can be theorized that during pregnancy and menstruation, when the ligaments soften, increased mobility will be found at the SIJ.

Mens et al. [14] developed a variation of the well known active straight leg raising test (ASLR). The supine patient is asked to lift one or both legs with a non-elastic SI belt (like the Serola Belt) compressing the SIJ. They used the belt in two different positions, one at a time; the high position is above the greater trochanters and the low position is at the level of the symphysis pubis. Each person gave their own assessment of whether lifting the leg(s) was easier with or without the belt. Twenty out of twenty-one had greater ease lifting their legs while wearing the belt. Seven people preferred the high position and ten preferred the low position, while four had no preference. Mens states that this ASLR test, with SI belt, could be suitable to quantify and qualify disability due to sacroiliac/symphysis pubis hypermobility. Mens quotes a Swedish gynecologist, Cederschjold, who stated that one characteristic of people with sacroiliac joint “loosening” was the “difficulty or almost impossibility of even moving the lower limbs” but noted “instantaneous relief in the pains and the ability to move the limbs when the hips are pressed hard together with the hands.” Mens, et al, used Cederschjold’s concept, along with their own observations on over 3,000 patients to develop the ASLR test association with a non-elastic sacroiliac belt. This test, either with a belt or with compression by hand, can be an excellent test to see if one has sacroiliac hypermobility and instability; if positive, a Serola Sacroiliac Belt should help with pelvic instability and pain.

Mens et al. [20] tested the validity of the ASLR and concluded “The ASLR test is a suitable diagnostic instrument to discriminate between patients who are disabled by PPPP (posterior pelvic pain since pregnancy) and healthy subjects and can be recommended as an instrument to diagnose PPPP. The test is easy to perform; reliability, sensitivity, and specificity are high. It seems that the integrity of the function to transfer loads between the lumbosacral spine and legs is tested by the ASLR test.”

In another study, Mens et al. [15], using Doppler imaging of vibrations, studied the laxity of the SIJ in women with pregnancy related pelvic girdle pain. All subjects also performed the Active Straight Leg Raise (ASLR) test without the belt and then with the belt in both the upper and lower belt positions. With the belt on, there was a significant decrease in laxity and a corresponding increase in ability to perform the ASLR test with the belt on. They suggested that either test can be a good diagnostic test for sacroiliac joint instability, with Doppler imaging of vibrations being more objective and the ASLR being simpler.

Walheim [21] states “One of the most common treatments for pelvic instability is a stabilizing sacroiliac belt.” He references Sahlstrand [22], in saying that “Pain is relieved and this is regarded as a confirmation of the diagnosis.”

In a study of 328 women, Fast et al. [4] tested the ability of the women to perform a sit-up exercise. They found that “Whereas all non-pregnant women could perform a sit-up, 16.6% of pregnant women could not perform a single sit-up… It may be concluded that during pregnancy the abdominal muscles become insufficient.” They also found that non-pregnant women who exercised regularly had less back pain than those non-pregnant women who did not exercise regularly. However, they said that “It seems that engaging in physical activities for four hours or more per week during pregnancy does not protect against backache and may even predispose the individual to LBP. The predisposition, however, was not statistically significant.”
MacLennan [23] reviewed the results of an earlier study which he participated in [24], and stated “The highest relaxin levels during pregnancy were found in patients who were the most incapacitated clinically. These results suggest there may be an association between high serum relaxin levels and pelvic pain and joint laxity during pregnancy. The women with the highest levels took the longest to recover after pregnancy.”

With regards to manipulative treatment, as early as 1958, Sands [25] described the development of a subluxation in saying “we see that backache of pregnancy occurs because the gradually increasing weight of the trunk of the pregnant woman has forced the wedge-shaped sacrum down between the bones of the sacroiliac joints, which have been softened by relaxin. In addition, the alteration in posture due to abdominal enlargement tends to displace the sacrum forward. This is facilitated by the greater width of the anterior surface of the sacrum as well as by the softening of the normally rigid fibrous union at the sacroiliac joints. The above mechanism results in a subluxation in many pregnant women… This subluxation lends itself to simple manipulative treatment.” In other words, this is a nutation lesion corrected by adjusting the sacrum toward counternutation.

Jungmann & McClure [26] state that the movement caused by gravity (nutation) becomes greater during pregnancy when the ligaments, which normally resist excessive rotation of the sacrum and ilia, become softened in preparation for birth. They also state that “The range of rotation is further increased if the ligaments become over-stretched and torn through excessive chronic pull of the body’s weight.” However, rather than ascribing this condition to an injury, they suggest it is the part of the natural aging process, which indicates its pervasiveness in the population. They describe a postural index, defined on x-rays, which demonstrates that, as one ages, the effects of gravity cause an increased separation of the sacrum and ilium, as we would see in the nutation lesion. They state that “The common characteristic properties of the chronic-progressive conditions, namely, ‘chronicity’ and ‘progressiveness’ are due to the facts that gravity works perpetually.”

A woman’s biomechanics are tremendously altered during pregnancy as the body adapts to new patterns of nutation and counternutation. The impact of labor and delivery on the musculoskeletal system is severe and, in many instances, complications arise involving the SIJ. Undoubtedly, the SIJ and symphysis pubis endure various levels of shock throughout each stage of pregnancy and postpartum as well. Circulation and stabilization of the SIJ are the most imperative principles when it comes to healing the pelvic floor after pregnancy. Several peer reviewed studies confirm that stabilizing the SIJ with an SI belt is a proven, sensible method for both preventing and relieving pregnancy related pelvic and back pain.

For additional resources on pregnancy and core stabilization, please read The Serola SI Belt in Pregnancy and Understanding the Vital Roles of Ligaments, Hormones and Exercise After Pregnancy.


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