The aim of this study was to investigate whether a single session of spinal manipulation of pregnant women can alter pelvic floor muscle function as measured using ultrasonographic imaging.
In this preliminary, prospective, comparative study, transperineal ultrasonographic imaging was used to assess pelvic floor anatomy and function in 11 primigravid women in their second trimester recruited via notice boards at obstetric caregivers, pregnancy keep-fit classes, and word of mouth and 15 nulliparous women recruited from a convenience sample of female students at the New Zealand College of Chiropractic. Following bladder voiding, 3-/4-dimensional transperineal ultrasonography was performed on all participants in the supine position. Levator hiatal area measurements at rest, on maximal pelvic floor contraction, and during maximum Valsalva maneuver were collected before and after either spinal manipulation or a control intervention.
Levator hiatal area at rest increased significantly (P < .05) after spinal manipulation in the pregnant women, with no change postmanipulation in the nonpregnant women at rest or in any of the other measured parameters.
Spinal manipulation of pregnant women in their second trimester increased the levator hiatal area at rest and thus appears to relax the pelvic floor muscles. This did not occur in the nonpregnant control participants, suggesting that it may be pregnancy related.
The role of the pelvic floor muscles (PFMs) in spinal stabilization has been well documented.1, 2 The PFMs are coactivated with the abdominal muscles particularly transversus abdominis during exercise and increases in intraabdominal pressure.3 The PMFs, also known as the levator ani muscle complex. are intimately involved in the birth process, mainly during the second stage of labor. The consequences of a difficult vaginal delivery, particularly when intervention is required, are strongly correlated to the development of PFM dysfunction. This often manifests as stress urinary incontinence, pelvic organ prolapse, and/or fecal incontinence.4, 5, 6, 7, 8 The social and economic cost of pelvic floor dysfunction is enormous.9
It has previously been demonstrated that sacroiliac manipulation significantly improves the feed-forward activation of the transversus abdominus.10 Lumbar spine mobilization has been shown to change the activation of the abdominal oblique muscles.11 Recently, real-time ultrasonographic imaging was used to demonstrate improved contraction of the transversus abdominus muscle following sacroiliac joint manipulation.12 As the PFMs are known to be coactivated with transversus abdominis,3 we hypothesize that sacroiliac and/or lumbar spine manipulation can affect PFM function.
Women who have increased bladder neck descent and a concomitant increase in levator hiatal area are more likely to have an uncomplicated vaginal delivery.13 If lumbopelvic manipulations are able to alter PFM function, then this could be beneficial during the second stage of labor. The ability of the PFM to stretch during vaginal delivery is highly likely to be related to the risk of PFM damage. Reduction in the incidence of PFM damage and consequent sequelae is a research priority.14 As the use of chiropractic care during pregnancy is becoming more popular, this technique could be of benefit in the future.
Chiropractic care is often used in the care of pregnant women, particularly for low back pain. A survey of 1531 women in South Australia found that 35.5% of women experienced moderately severe low back pain during pregnancy and that two-thirds of this group had persistent back pain following pregnancy.15 A study of obstetric caregivers and pregnant women in New Haven, CT, found that 61.7% of the pregnant women and 36.6% of the obstetric caregivers would consider chiropractic care for low back pain during pregnancy.16 A retrospective study of 400 pregnancies and deliveries was undertaken by interview of 170 consecutive female patients presenting to 5 chiropractic offices in the Niagara Peninsula in Canada. Back pain was reported during 42.5% of the pregnancies and 44.7% of the deliveries. Those that had received manual manipulation reported significantly less pain during labor.17 A retrospective case series studies found that chiropractic care, averaging only 1.8 visits, led to clinically important improvement in 16 of 17 cases of low back pain in pregnancy with no adverse effects.18
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