Postural Changes Associated with Pregnancy - Dissertation Example

?TABLE OF CONTENTS INTRODUCTION 2 2.PURPOSE 3 3.AIMS AND OBJECTIVE OF THE STUDY 4 4.BACKGROUND 5 A.Causes of postural changes during pregnancy 5 Centre of Mass (COM) 5 Connective Tissue Laxity 6 B.Types of Postural Changes: 8 Lumbar Lordosis and Sagittal Pelvic Tilt Increase (Whitcome, 2006) 8 Lumbar Lordosis Reduction (Moore et al. 1990): 9 Increase in Lumbar Lordosis and Thoracic Kyphosis (Bullock-Saxton, 1991) 10 Thoracolumbar Spinal Curve Flattening (Gilleard et al., 2002) 10 C.Postural Changes Associated With Sitting and Standing Stances 11 5.METHODOLOGY 17 Sampling, recruitment and selection of participants 17 Ethical considerations 18 Methods of data collection 18 Procedure 18 Methods of data analysis 19 Timetable 19 Resources required 19 Critique of Strengths and Weaknesses of Proposal 19 6.RECOMMENDATIONS 20 7.CONCLUSION 21 REFERENCES 22 POSTURAL CHANGES ASSOCIATED WITH PREGNANCY 1. INTRODUCTION Posture is defined as the arrangement of body parts with reference to each other. Thus a good posture refers to the optimum alignment of musculoskeletal system so as to enable body movement with maximum efficiency (Britnell et al., 2005). Pregnancy brings about multiple changes in the women’s body affecting almost every biological system. While some of these changes go with pregnancy, others continue to affect for longer duration. There is an increase in body mass and dimensions with non-uniform distribution of both of these parameters. Thus the centre of gravity of the body and therefore, its equilibrium is disturbed and in order to regain it the body must lean backwards. The skeletal and muscular system of the women’s body undergoes several biomechanical changes to accommodate the growing uterus, maintain body balance and facilitate smooth delivery. Moreover the hormonal changes during pregnancy too affect the musculoskeletal system. Later weeks of pregnancy are characterized by lordosis or a significantly increased curvature of the spine. Thus changes are observed in both the static and dynamic posture of the women during pregnancy. Along with these postural changes are observed discomforts such as low back pain which may or may not be associated with the postural changes. Moreover the postural changes have also been linked to increased vulnerability to fall incidences. Research has shown that the major postural adaptations associated with pregnancy include forward shift in centre of gravity, and subsequent anterior pelvic tilt, with some cases of lumbar lordosis and thoracic kyphosis. Approximately 75% of women exhibit a more posterior posture wherein the mass of the expanding uterus with the fetus is shifted posterior to the prior centre of gravity (Britnell et al., 2005). While pregnancy itself is associated with different levels of multiple discomforts both physical and mental, an understanding of the mechanism and nature of changes associated with pregnancy is imperative for developing measures to deal with these problems. This literature review aims to study the various aspects of postural changes associated with pregnancy. 2. PURPOSE Bipedalism is a distinguishing character of hominids and the human skeleton has developed several adaptations to enable it. One of the chief adaptations was an elongated lumbar region with both an increased length of individual vertebra and also increase in number of vertebra. Besides this, the lumbar vertebra are also arranged in a significantly concave curve, the feature being specifically termed as lumbar lordosis. As a consequence of lumbar lordosis the trunk’s centre of mass (COM) is shifted to a position above the hips thereby imparting stability to the upper part of body (Whitcome et al., 2007). The second major adaptation is sagittal pelvic tilt. Human posture and motion is thus defined by two biomechanical components responsible for imparting stability viz lumbar lordosis and sagittal pelvic tilt. However, pregnancy related marked changes in body shape and mass pose significant challenges to the bipedal stability (Whitcome et al., 2007). Advancement of pregnancy is characterized by fetal growth resulting in body mass increase most of which is located in the abdominal region of the female body leading to an increase in area, as well as disproportionate weight distribution. Besides the growing fetus leading to expansion of uterus, enlargement of breasts, increase in blood volume and fluid retention by the maternal body are other factors contributing to overall weight gain during pregnancy. On an average a pregnant women should gain 10-12 kg during the entire term of pregnancy but more than 60% of women remain short of this value. Still there is considerable weight gain during pregnancy; approximately half of which is concentrated in the abdominal region and anterior to the line of gravity. As a consequence the COM of body is shifted to the frontal part of the body, this added to the relatively smaller base provided by the two feet (compared to four in tetrapeds); the fetal position reduces upper body stability during pregnancy (Whitcome et al., 2007). The positional shift in COM thus induces alterations in the biomechanics of posture and gait during pregnancy. 3. AIMS AND OBJECTIVE OF THE STUDY The proposed research aims to study the postural changes associated with the different stages of pregnancy in Homo sapiens. In order to achieve this aim, the following objectives would be pursued during the course of this study: 1. Identification of the specific biological parameters that define and determine the body posture in a healthy individual. 2. Following practical methods for the accurate assessment of the aforementioned biological parameters. 3. Estimation of the biological parameters determining and defining body posture in humans in maternal subjects at regular intervals throughout the term of the pregnancy and for two months after child birth. 4. Investigation of the postural changes on the basis of the specific biological parameters that define posture and the pattern of change in their values with advancement of pregnancy. 5. Correlating the physical outcomes of determining factors of posture with the postural changes observed with the advancement of pregnancy. 4. BACKGROUND A. Causes of postural changes during pregnancy The two recognized causes of postural changes associated with pregnancy are altered centre of gravity and hormone induced laxity of connective tissues. Centre of Mass (COM) One of the chief studies supporting the association between COM and postural changes was conducted by Dumas and associates (2009). Based on the hypothesis that the change in posture during pregnancy results as a consequence of three factors, namely increase and redistribution of body weight, alteration of joint laxity and lengthening of abdominal muscles, a test was designed to test the relevance of prior two factors. 94 subjects with 33 pregnant women and 61 controls participated in the study. Preliminary data for age, body mass, height and parity was recorded. Photographs were taken of the spine for self selected postures along with data for body line of gravity. It was deduced from the data collected that the curvature of the lumbar region of the body exhibited a rise. However the line of gravity did not change. Despite the lack of data for position of COM, the study is clearly indicative that the changes in curvature of lumbar region facilitate body balance in pregnant women. The evidence for the association between COM and lumbar lordosis and sagittal pelvic tilt was provided by Whitcome (2006) in a longitudinal study on 25 pregnant women. The study recorded data on circumference, stature and mass of body; Kinetic measurements of maternal COM, three dimensional position data for stationary and walking stance; followed by calculation of lordotic and sagittal pelvic tilt angles at gestational stage corresponding to 0%, 20%, 40%, 60%, 80%, and 100% fetal weight. It was deduced on the basis of data acquired that lumbar lordosis and sagittal pelvic tilt are both induced at gestational stage corresponding to 40% fetal weight, and further increase in correlation with advancement of pregnancy and rise in fetal weight, attaining a peak at 37weeks of gestation. Under conditions of imposed posture maintaining normal body angles and lacking these adjustments; the body COM was found to undergo 3.2cm anterior shift relative to all joints of the lower body namely hip, knee and ankle during the period spanning end of first trimester to end of third trimester (Whitcome, 2006). Connective Tissue Laxity Joint discomforts and joint laxity are common features associated with pregnancy. One of the most remarkable implications of this alteration is relaxation of sacro-illiac synchondroses and symphisis pubis. The process begins towards the end of first trimester and reaches its peak towards the term end. Relaxation of pelvic joint is in fact an important adaptation for vaginal delivery. However the general significance of joint laxity is still not completely understood. It has been reported that laxity is usually more intense in primigravidas and such individuals also suffer less back pain compared to those with less joint laxity (Whitcome, 2006). Joint laxity has been correlated by some researchers with the four major hormones of special significance during pregnancy namely, relaxin, produced by corpus luteum during pregnancy; and cortisol, estrogen and progesterone, while some other researchers have reported a lack of clear association between these hormones and joint laxity. A study was conducted by Marnach et al. (2003) to study the nature of relationship, if any between the levels of these hormones and increased joint laxity. The subjects were 46 pregnant women who were followed through their pregnancy up to six weeks post partum. Data for wrist joint laxity for flexor-extension and medial lateral deviation was recorded using clinical goniometer and corresponding serum levels of the four hormones was estimated. The results are in confirmation of the other researches with respect to definite enhancement of joint laxity with advancing pregnancy. Even though joint laxity could not be linked with joint discomfort, the latter could result as a consequence of cumulative effect of joint laxity, increase body weight and anterior shift in COM. Further the levels of the four hormones studied were found to rise with progress of pregnancy (Marnach et al., 2003). Estrogen has previously been linked to relaxin receptor expression in animal studies causing pelvic joint loosening during pregnancy. A study on rodents too has specifically linked relaxin levels to pelvic joint laxity. Studies on humans have not been able to provide clear results on correlation of any specific hormone or hormone set on joint laxity. In the study by Marnach and associates (2003) however, estradiol and progesterone levels were found to be correlated with joint discomforts which can be due to the various receptors available for these hormones (table 1). Table 1: Correlation of serum hormone levels with peripheral joint laxity Joint laxity along with shifted COM leads to loss of balance, both factors getting intense with advancing stages of pregnancy and thereby leading to adaptations in form of postural changes. B. Types of Postural Changes: Lumbar Lordosis and Sagittal Pelvic Tilt Increase (Whitcome, 2006) The study by Whitcome (2006) clearly demonstrates that there is a remarkable rise in lumbar lordosis curvature and sagittal pelvic tilt occurring simultaneously during pregnancy suggesting a common factor underlying their origin. Moreover quantitative estimation of these two factors and the body COM gives definite evidence that the angular changes in lumbar lordois and sagittal pelvic tilt occur as a consequence of rise in spine loading and are counteractive measures to overcome the instability resulting due to anterior shift of COM. This evidence was further supported by follow up studies at postpartum stage, which was characterized by substantial reversal of angular changes in curvature, even though the curvature did not return to pre pregnancy state. Earlier studies have demonstrated the rise in lumbar lordosis parallel to and probably caused by weight gain and joint laxity. However, in the final eight weeks of pregnancy lordosis was found to be influenced by parity. Figure 1: Lordosis and Increase in Body Mass with Advancing Stages of Pregnancy Lumbar Lordosis Reduction (Moore et al. 1990): A longitudinal study by Moore et al. (1990) analyzed postural changes associated with pregnancy by gathering data on lumbar lordosis, kyphosis and position of line of gravity. The study used data gathered from 30 pregnant subjects with monthly follow ups till the term of pregnancy and also post partum. The deductions made on the basis of data gathered revealed a flatter spinal curvature in contrast to other studies which reported an increase in lumbar lordosis and enhanced curvature of spine. There was lack of sufficient evidence describing kyphotic curvature and the line of gravity was found to definitely remain in the same position. Moreover the incidences of occurrence of low back pain were found to be inversely related with changes in lumbar lordosis. Increase in Lumbar Lordosis and Thoracic Kyphosis (Bullock-Saxton, 1991) A research conducted by Bullock-Saxton involved the study of spine curvature and pelvic tilt for the period spanning pregnancy and post natal period up to 2 months post delivery. Significant changes in the lumbar lordosis and thoracic kyphosis was observed. Lumbar lordosis was found to increase significantly and the increase remained for the post natal period studied. Kyphosis or the curve of spine causing a slouching posture due to rounding of the back too was found to be significantly increased, leading to mid back pain and difficulty in breathing in some subjects. Thoracolumbar Spinal Curve Flattening (Gilleard et al., 2002) A longitudinal study was conducted by Gilleard and associates (2002) to investigate the postural alterations of the trunk during pregnancy. Data was gathered for sitting and standing postures from 9 pregnant subjects and 12 controls. The study design involved repeated measures of systematic alterations of pelvic, thoracic and head segments as well as the thoracolumbar, cervicothoracic spines and also right hip joint. Upper trunk posture was found to remain unaltered in most subjects with a few of them exhibiting a flatter thoracolumbar spine during sitting with advance of pregnancy. Spine curvature is indicative of the amount of mechanical work required to maintain oneself in an upright position. Increase in curvature reduces the amount of work needed to do so. Thus reduction in curvature causes the trunk muscles to tire rapidly due to continuous upright posture. (Gilleard et al., 2002). C. Postural Changes Associated With Sitting and Standing Stances Study by Dumas and associates (2009) aimed to study the posture and muscle activity of the back and upper extremity of pregnant subjects in comparison to non pregnant subjects. The results indicated a more upright posture adapted by the pregnant subjects with discomfort in lower back and pelvis area. Different studies on postural changes for quiet standing stance have given widely varied results; stressing the existence of alterations, but varying in nature of alterations (Bullock-saxton, 1991; Moore et al, 1991). While some studies report an increase in lumbar lordosis (Bullock-Saxton, 1991), others report a decrease in same (Moore et al, 1991). Reports of lack of significant change too have been reported for pelvic inclination, sacral base inclination, thoracic kyphosis, and lumbar lordosis (Gilleard et al., 2008). Thus raising doubts about the methodology of these researches and uniformity of nature of postural changes in individual subjects. Gilleard and associates’ (2008) study of the standing stance revealed similar postures in control and early pregnancy subjects. Even with advance of pregnancy, the mean values for postural parameters remained similar for control and pregnant group; however large variance was observed in the individual values for pregnant subjects compared to mean value indicating that individual responses to anatomical and physiological changes associated with pregnancy is different and cannot be generalized. A longitudinal study on pregnant women attempting to stand rising from a chair, reported several kinetic and kinematic adaptations enabling them to maintain balance while standing. These adaptations aimed to widen the support base, enhance thoracic segment motion, and lower the trunk-thigh apposition. Extra caution resulted in lower propulsion in order to ensure stability during standing (Gilleard et al., 2008). Studies of gait pattern during pregnancy clearly indicate normal gait pattern so that the speed of walking, stride length and cadence remain unaltered. However, the normalizing of the gait pattern is made possible as a consequence of compensatory mechanisms such as broadened base facilitated by increased distance between the feet (Gilleard et al., 2008). Thus there definitely are less obvious biomechanical changes which are responsible for maintaining the apparent uniformity in the gait pattern of pregnant women with respect to non pregnant. Many other researches however, have given results contradicting the apparent normality theory provided above. A reduction in comfortable walking velocity has been reported, in condition where pregnant individuals walked at a self selected walking speed. In another study by Foti and colleagues showing no apparent differences in conventional parameters, remarkable divergence was reported in support phase timing. Longer part of gait period involved double support phase, indicating attempts to achieve normalcy by obtaining additional base support. Moreover hip abduction moment too was found to be larger (Whitcome, 2006). Foti and associates analyzed gait biomechanics in 15 subjects in the second half of the last trimester of their pregnancy. Data collection process involved three dimensional gait analysis on the basis of multiple parameters namely velocity, stride length, cadence, single support walk time and double support walk time. Overall gait kinetics remained unchanged during pregnancy although individual differences were found especially in the pelvic tilt, which ranged from a decline of 10 degrees to a rise of 13 degrees. However, the mean value for the population studied was only four degrees. It was also reported that the gait kinetics were maintained as a consequence of substantial rise in the hip and ankle gait parameters (figure 2). These results are indicative of the rise in stress on hip abductor, hip extensor and ankle plantar flexor muscle during walking as a consequence of pregnancy. Figure 2: Changes in Gait Parameters during Pregnancy and 1 year Postpartum Initial observations of gait pattern post optimization of joint angles, moment, power of hip, knee and ankle joint, reveal lack of any significant differences in pregnant subjects and non pregnant individuals. However an analysis of hip joint centre of pregnant women after optimization reveals significant variations in knee abduction angle, hip power, hip extension moment, knee and hip internal rotation angles. Hip is the major load bearing organ and stress on hip extensors is intensified during pregnancy leading to fatigue and even pain. Thus, the two factors namely, base support and hip parameters; together help to counteract the increase in body weight and widening of pelvis due to ligament laxity, and thereby; maintain balance. Maintenance of stride length too is made possible by lower amplitudes of pelvic rotation during walking, due to restricted thoracic rotation as a consequence of fetus present in the abdomen. The additional weight too restricts the rotation of otherwise widened pelvic, thus keeping the stride length low. Gilleard and colleagues (2008) have reported a list of adaptations related to trunk motion affecting gait pattern during pregnancy on the basis of studies using two pattern recognition techniques namely support vector machine (SVM) and linear discriminant analysis (LDA). The studies were used to understand the trunk kinematics in subjects at later stages of pregnancy compared to non pregnant controls. The results were indicative of changes in pattern of musculoskeletal load bearing rendering the trunk vulnerable to discomfort, pain and injury. The physical adaptations enabling comfort during pregnancy and preparing the maternal body for the process of child birth also have many other implications. The postural changes caused due to growth of fetal mass, overall rise in maternal body weight, shift in COM of maternal body and changes in joint laxity could be the causes leading to backache in pregnant women which is an almost regular feature associated with pregnancy. A study was conducted by Bullock and associates (1987), to investigate the correlation between postural changes associated with pregnancy. A group of 34 subjects attending a prenatal clinic were studied and data was gathered for progressive changes in levels of thoracic kyphosis, lumbar lordosis and sagittal pelvic tilt on the observations of the related parameters of spine and pelvic joint. Back pain assessment too was simultaneously conducted. The study showed a significant increase in spine curvature attributed both to lumbar lordosis and thoracic kyphosis. The fifth to the ninth months were found to be associated with significant postural changes and simultaneous development of back pain was reported by 8 of the 14 subjects. However besides this no further correlation was found between the spine curvature changes and back pain. It was speculated that factors besides these, such as joint laxity due to hormonal changes may be the causal forces behind back pain (Bullock et al., 1987). Earlier authors such as Danforth (1967), Epstein (1959) and Spankus (1965) had reported the association of enhanced lumbar lordosis with postural changes; and also attributed the postural changes as a mechanism of maintaining balance. Spankus had experimentally demonstrated the occurrence of significant changes in spine curvature in both lumbar and thoracic region. However, reports of specific changes in kyphosis were lacking in earlier studies, the first to provide information on this aspect being Bullock and colleagues. Significant alterations in kyphosis were reported in some women accompanied by severe pain, while the same was lacking in subjects that did not experiencing pain (Bullock et al., 1987). Although kyphosis exclusively cannot be considered as the cause of postural changes and pregnancy related back pain, a deeper study of this factor may lead to significant results. While it has been now established that postural adaptations enable pregnant women to carrying the extra load, there are different opinions as to specific postural adaptations enabling it. Some earlier authors such Rhodes (1958), Danforth (1967), Epstein (1959) and Spankus (1965) and some of the recent ones such as Bullock et al. (1987), (Bullock-Saxton, 1991), Whitcome (2006) have reported an increase in lordosis as the cause of these postural changes. Some other authors such as Cyriax (1965), Snijders et al (1976) have reported a flattening of spine due to decrease in lumbar lordosis as the cause of postural changes. They have proposed that spine pulls back to accommodate the growing fetus (Bullock et al., 1987). The study by Dumas and associates (2009) investigated various factors contributing to postural changes along with recording of data for age, height etc, but overlooked a probable factor, i.e. lengthening of abdominal muscles and its role in postural changes. Earlier studies have indicated an apparent uniformity in gait pattern of pregnant subjects, with minimal anterior tilt of pelvis in sagittal plane, however generalizations cannot be made on the basis of these results. The same study also reported a substantial proportion of subjects (six of fifteen) with similar or decrease anterior tilt of the pelvis. An increase in pelvic tilt is usually associated with an enhanced lumbar lordosis and is an attempt to maintain an upright posture, while the slight increase in height reported for some women is indicative of lowering of lumbar lordosis. Thus individual differences are common in postural studies during gait patterns related to pregnancy. There is no definite data on the association of postural changes and back pain in pregnancy. Earlier authors such as Haslam and Huchinson; Sands; and Spankus; considered back pain in pregnancy to be a ‘normal state’ and not worth research or therapy. Spankus has provided the explanation that the nature and rapidity of the process of pelvic rotation during pregnancy led to undue stress on musculoskeletal system resulting in back pain. However since these studies lacked statistical data, they were not given scientific importance in designing therapeutic measures (Bullock et al., 1987). Study by Bullock and associates (1987) found correlation between kyphosis alterations and back pain, but the same could not be said for lordosis or sagittal pelvic inclination. Abdominal dimensions increase with advancing stages of pregnancy mainly due to adipose tissue deposition and the gravid uterus. In early stages the posture is normal with respect to sagittal plane alignment of head, pelvic and thoracic segments as well as spine during upright sitting. Even with advance of pregnancy, there are no significant differences reported for posture during upright sitting. Moreover no specific trends are observed in the population studied. So the postural changes if any, are more individual in nature and cannot be generalized. Very few researches are done with the aim of studying postural changes during sitting. A comparatively flatter curve of the spine during upright sitting has been reported in some subjects during a study by Gilleard et al. (2008). This results as a consequence of an enhanced posterior sagittal plane orientation of pelvic segment and increased flexion of thoracolumbar spine. However, the loss of spine curvature has severe negative implications since it intensifies vertical forces due to spinal load making the individual susceptible to injuries. 5. METHODOLOGY Sampling, recruitment and selection of participants An equal number of pregnant and non pregnant women, minimum of ten for each group will be recruited for the study. The Samples will be selected from women coming to the clinic for routine prenatal checkups. The control group will be randomly selected from the population of the area visiting the clinic for minor ailments. The selection criteria for the maternal group includes an age range of 20-40yrs, height of 154-172cm, and in the first month of pregnancy. Maternal subjects will be selected so as to include an equal number of primigravidas and multigravidas. The control group would include healthy female subjects with no prior incidence of pregnancy and fulfilling the criteria of age and height as defined for the maternal group. Ethical considerations Informed written consent will be obtained from both the maternal and control group of participants. Each of the participants will be individually explained the procedure to be followed and the tests to be conducted along with an agreement for confidentiality. Methods of data collection Data collection will be started at 4 weeks of pregnancy for the maternal subjects and at the same time for the control group and next follow ups will be conducted at intervals for 4 weeks for the maternal group and 8 weeks for the control group. For data collection subjects will be dressed in closely fitted clothing, and markers will be placed to obtain data for head, thorax, pelvis and right thigh. Data for head and thorax would be used to study postural changes in upper body and that of pelvis and thigh for that of lower body. Data for each of the body segments would be obtained by placing three 2cm diameter noncolinear retroreflective markers. To reduce chances of errors due to variable marker placement, all markers would be placed by single individual. An expert visionTM motion analysis system with eight 8mm video camera will be used for data collection. Procedure For the standing stance, participants will be asked to stand in a relaxed position and totally at comfort. Their arms are to be placed at the sides and eyes directed straight at the eye level marker. For sitting stance, they would be told to sit in an upright position, on a stool, again with arms at the sides and eyes at the eye level marker. Methods of data analysis A repeated measure ANOVA would be done for each of the variables obtained at every visit. The results of the ANOVA will be used to detect the pattern of changes associated with the advance of pregnancy in the maternal group, and would be compared with the similar data obtained from the control group. Timetable Baseline check up would be done for the maternal subjects at fourth week of pregnancy or earlier, along with simultaneous data collection for the control group. Follow ups would be done at every fourth week following the baseline visit i.e. 8, 12, 16 and so on, continuing till after 8 weeks of child birth. For the control group data will be collected at once in two months period and the final visit by the two would occur simultaneously. Resources required Sampling and recruitment of participants would require affiliation with a maternity clinic or a hospital dealing with gynecological cases. Data collection would require periodic access to an expert visionTM motion analysis system. Critique of Strengths and Weaknesses of Proposal The procedure followed would enable data collection for a large number of variables associated with postural alignment. Data collected and the trend of alterations observed in these variables, during the course of pregnancy and post partum would enable simultaneous identification of factors being affected as a consequence of pregnancy associated changes, as well as study of the pattern of changes in the variables. Thus objectives 1 to 4 of the research would be achieved. The two major weaknesses of the proposal are the lack of data for the pre pregnancy posture of the maternal subjects, which would definitely affect the postural alignment during the post pregnancy stages. The small number of samples would reduce the accuracy of statistical analysis. However, frequent follow ups and use of latest technology can definitely enable precise data collection and sense minor deviations in the variables. 6. RECOMMENDATIONS Pregnancy with its multiple aspects is one of the most studied and least understood of the biological phenomenon, mainly due to the numerous intricately woven biological processes simultaneously contributing to the main event and affecting all parts body (Bullock et al., 1987). Moreover postural changes associated with pregnancy have been mainly studied as causal factors for back pain and not as individual processes and hence reports of investigations of the underlying mechanisms of postural changes are scarce. Further, due to the studies being characterized by various procedural shortcomings, and the complexity of the factors involved, researchers have failed to build a consensus as to the nature, mechanism and consequences of postural changes associated with pregnancy. For understanding an aspect of pregnancy, data needs to be gathered for all features of the patient, even for those variations which may not appear to be directly related to the condition. A comprehensive study involving large number of subjects with long term follow ups is required for understanding pregnancy and the associated postural changes. 7. CONCLUSION Biomechanical changes during pregnancy are a joint effect of chemical changes namely, changes in the levels of various hormones leading to joint laxity; and musculoskeletal adaptations to maintain balance despite the increasing weight and anterior shift of maternal COM. While on one hand this prepares the maternal body for vaginal delivery, it also helps women maintain balance while standing, walking and changing stance such as sitting to standing. The major negative outcome of this has been reported to be back pain, though clear evidences linking the two are still lacking. Since most of the reports available are conflicting and individual in nature; researchers need to design studies with larger number of subjects and record data for multiple variations occurring during various stages of pregnancy. REFERENCES 1. Britnell, S. J., Cole, J. V., Isherwood, L., Sran, M. M., Britnell, N., Burgi, S., et al. (2005). Postural health in women: the role of physiotherapy. JOGC MAI , 493-501. 2. Bullock-Saxton, J. E. (1991). Changes in posture associated with pregnancy and the early post-natal period measured in standing. 103-9. 3. Dumas, G. A; Upjohn. T. R; Charpentier, K., Leger, A., Plamondon, A., & McGrath, M. J. (2009). Posture and muscle activity of pregnant women during computer work and effect of ergonomics. International Journal of Industrial ergonomics , 313-25. 4. Gilleard, W. L., Crosbie, J., & Smith, R. (2002). Static trunk posture in sitting and standing during pregnancy and early post partum. Archives of physical medicine and rehabilitation , 1739-44. 5. Gilleard, W., Lai, D. T., Levinger, P., & Begg, R. K. (2008). Detecting trunk motion changes due to pregnancy using pattern recognition techniques. Conf Proc IEEE Eng Med Biol Soc , 2405-8. 6. Marnach, M. L., Ramin, K. D., Ramsey, P. S., Song, S. W., Stensland, J. J., & An, K.-N. (2003). Charactrization of the relationship between joint laxity and maternal hormones during pregnancy. Obstet Gynecol , 331. 7. Moore, K., Dumas, G. A., & Reid, J. G. (1990). Postural changes associated with pregnancy and their relation with low back pain. Clinical biomechanics , 169-74. 8. Whitcome, K., Shapiro, L. J., & Lieberman, D. E. (2007). Fetal load and the evolution of lumbar lodosis in bipedal hominins. Nature , 1075-8. Read More