Background

Pelvic girdle pain has been described as pain experienced between the posterior iliac crest (inferior to L5) and the inferior gluteal folds, particularly near the sacroiliac joints, and pain may radiate in the posterior thigh and can occur in conjunction with or separate from pain in the symphysis [1] (pp797). Women commonly experience pelvic girdle pain during pregnancy, with reported prevalence of Pregnancy-related Pelvic Girdle Pain (PPGP) ranging from 23 to 65% depending on the study methods used [2,3,4]. Women with PPGP often have impaired mobility, with 7 to 12.5% having to use crutches or a wheelchair [5,6,7]. PPGP symptoms affect their ability to cope with everyday life for which they feel unprepared and which they feel is not acknowledged [8,9,10]. PPGP is also a leading cause of sick leave during pregnancy [11,12,13].

The aetiology of PPGP remains uncertain but hormonal and mechanical factors have been suggested. Regarding hormonal factors, the main focus has been on the hormone relaxin, which is thought to increase pelvic laxity, yet evidence from clinical studies examining the association between relaxin and PPGP is of low quality with inconsistent results [14]. Biomechanically, there is moderate evidence that PPGP is associated with altered motor control, kinetic and kinematic parameters [15]. Knowledge of risk factors for PPGP can guide the development of preventative and management strategies, and can then lead to development of predictive models [16]. Existing narrative reviews, guidelines, background sections of primary studies and patient information vary widely in what they report as risk factors for PPGP and often seem conflicting when compared [1, 17, 18]. In their paper on the clinical presentation of PPGP, Wu et al. [19] included a structured review on risk factors and interpreted evidence as strong, weak, conflicting, or no evidence based on the number of studies, but numerous studies have been published since then.

The high PPGP prevalence, the increase in published studies on PPGP and the conflicting information in narrative accounts presented a clear need for a scoping review to examine and provide a comprehensive overview of the literature on risk factors for PPGP. A scoping review is a form of knowledge synthesis that maps, summarises and synthesises the evidence on a certain topic [20]. Scoping reviews may also be conducted to determine the value and scope of a full systematic review [21]. Preliminary searches identified a potentially large number of risk factors examined. Hence, a scoping review was perfectly placed for a thorough exploration of the literature to inform future systematic reviews. The aim of this scoping review was thus to map the body of literature on risk factors for experiencing PPGP and to identify research gaps.

Methods

We searched five electronic databases (3 August 2020) including PubMed, Embase, CINAHL, PsycINFO, and MIDIRS with no time filters used. We also searched ClinicalTrial.gov (3 August 2020) for relevant registered studies. Only studies reported in English were included, but no language filter was applied to assess publication bias. We inspected reference lists of included studies and contacted experts in the field. The full search strategy is presented in Additional file 1.

Two review authors (FW, DD) independently reviewed all citations by title and by abstract. Where there was a lack of consensus, citations were moved to full-text selection. Any disagreement at full-text selection was resolved by discussion, and if necessary, involving a third reviewer. The selection criteria are presented in Table 1. Data were extracted independently by FW and DD using a piloted review-specific data extraction sheet. Data extracted included the year and country of publication, study design, setting, inclusion and exclusion criteria, number and characteristics of participants, the exposure and outcome measure(s) and how these were assessed, the number of participants with/without a certain exposure and outcome, and the risk estimates. Consensus was sought and, in addition, 25% of data were rechecked. Findings were summarised narratively and we have provided an overview of all factors examined in the literature in Tables 3, 4, 5 and 6. To map the existing literature on risk factors for PPGP, findings were grouped by trimester of pregnancy (first, second, third or any trimester/trimester not specified), by type of factor (physical, psychological, socio-demographic), and by whether they were examined in more than one study or not.

Table 1 Scope of the scoping review
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Results

We identified 5090 records from database searches. After duplicate removal, 3899 records were screened by title, 390 records by abstract, and 261 by full-text, of which 24 records met the inclusion criteria (Fig. 1). A total of 1077 records were identified from ClinicalTrials.gov one of which was eligible for inclusion but was a duplicate. Studies excluded at full text are listed by reason for exclusion in Additional file 5.

Fig. 1
figure 1

Flow chart of search results and study selection

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Five of the 24 included studies involved the same cohort, but because different risk factors were examined and reported in the publications, they were all included in the review [25, 28, 30, 31, 43]. The characteristics of the 24 included studies are presented in Table 2. Twelve prospective cohort studies, three retrospective studies and nine cross-sectional studies, published between 1995 and 2015 in Norway (n = 13), Sweden (n = 3), Denmark (n = 2), Japan (n = 1), Israel (n = 1), United Kingdom (n = 2), Brazil (n = 1) and Spain (n = 1), were included. All but one study [43] included both nulliparous and multiparous women, and only one study reported results separately for first-time mothers [28]. Eight of the 24 records examined the outcomes of low back pain or lumbopelvic pain during pregnancy in addition to PPGP outcomes, but only PPGP data were included as per review scope. Participants of 20 included studies completed self-reported questionnaires, three studies collected data from medical records [39, 42, 44] and one study conducted structured interviews with women [41]. Three studies also included a physical examination to assess for PPGP [24, 29, 40]. Seven studies examined the outcome Pelvic Girdle Syndrome (PGS), which is considered a subgroup of PPGP, defined as experiencing pain in the symphysis pubis and both sacro-iliac joints [24, 25, 28, 30, 31, 36, 43]. Seven studies examined pain at the anterior pelvic girdle as outcome, using the terms symphysiolysis [23, 41, 42], symphysis pubis dysfunction [44, 45] or pubis pain [34, 46]. Due to these differing inclusion criteria, methods of study, and stages of pregnancy or postpartum, few studies could be identified that would be suitable for meta-analysis in a future systematic review. As these occur, they are noted, and results on all other factors are presented in narrative format.

Table 2 Characteristics of included studies
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Risk factors for PPGP examined in more than one study

Eleven physical and three socio-demographic potential risk factors were examined in more than one study (Table 3). Findings are also provided in extended tabular format in additional file 2.

Table 3 Risk factor for PPGP examined in more than one study
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A history of low back pain was a risk factor for PGS [24, 25] and for PPGP [4, 40]. Low back pain [4, 35] and pelvic girdle pain [35, 40] in previous pregnancies were also positively associated with PPGP. Women with an older age of menarche were at increased risk of PGS [30] and PPGP [37]. Nine studies examined parity as risk factor [23,24,25, 33, 35, 36, 38, 40, 45] and all but two studies [36, 40] found that parous women were more likely to have PPGP. Eight studies examined the relationship between smoking and PPGP and findings were conflicting with most studies finding no statistically significant association [4, 24, 25, 34, 37, 40]. Eight studies examined Body Mass Index (BMI) as a risk factor, with conflicting results. The relationship between pre-pregnancy weight and PPGP was conflicting but it was positively associated with PGS (n = 1880; AOR 1.03; p < 0.05) and symphysiolysis (“pain at the symphysis pubis”) (n = 1771; AOR 1.04; p < 0.05) [24]; however, only three studies examined this factor [4, 24, 40]. Two studies (n = 2224; n = 1149) found that maternal height was not a risk factor (p > 0.05) [4, 24]. The evidence concerning the association between PPGP and the weight of the newborn was conflicting [33, 37].

For socio-demographic factors, age was examined in seven studies with differing results. Four studies examined educational level of which three found that women with no university qualification were more at risk of PPGP (n = 946; OR 1.3 [1.0–1.8]; p = 0.03) [4], posterior PPGP (n = 2439; OR 1.3 [1.0–1.8]; p = 0.04) [38], and PGS (n = 21,397; AOR 1.3 [1.1–1.4]; p < 0.001) [25]. However, Malmqvist et al. [35] found no association between the years of education and moderate/severe PPGP (n = 306; SMD 0.03 [− 0.2–0.3]). Higher work satisfaction (2 studies) was associated with a reduced risk of PGS (n = 1880; AOR 0.9; p < 0.05) or double-sided sacro-iliac syndrome (n = 1314; AOR 0.9; p < 0.01), but not with single-sided sacro-iliac syndrome (n = 1961; p > 0.05) or symphysiolysis (n = 1771; p > 0.05) [24]. Evidence on the association between gestational diabetes and PPGP was conflicting [34, 42].

Risk factors for PPGP in the second trimester of pregnancy examined in one study

Berg et al. [23] examined two physical potential risk factors for symphysiolysis in the second trimester and found no association with heavy or very heavy physical workload whether this included lifting movements (n = 451; OR 1.3 [0.6–2.5]; p = 0.5) or not (n = 513; OR 1.1 [0.6–2.1]; p = 0.7) (Table 4).

Table 4 Risk factor for PPGP in the second trimester examined in only one study
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Risk factors for PPGP in the third trimester of pregnancy examined in one study

Forty-two physical factors, nine psychological factors and two socio-demographic potential risk factors for PPGP in the third trimester of pregnancy were examined in ten studies (Table 5). Findings are also provided in extended tabular format in additional file 3.

Table 5 Risk factor for PPGP in the third trimester examined in only one study
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A history of postpartum low back pain, was positively associated with PPGP in the third trimester (n = 1164; OR 2.0 [1.4–2.8]; p = 0.0002) [4]. Women who had physically demanding work (4-point likert scale) were more likely to have PGS (n = 68,872; AOR 1.4 [1.4–1.5]; p < 0.001) [25]. A heavy or very heavy physical workload (n = 513; OR 1.9 [1.1–3.3]; p < 0.05) and a heavy or very heavy physical workload including lifting movements (n = 513; OR 1.9 [1.2–3.0]; p < 0.05) were also associated with an increased risk of symphysiolysis [23]. Women with pubic symphysis pain reported higher pain (n = 268; AOR 35.5 [19.7–51.1]; p < 0.001) and disability (n = 268; AOR 11.8 [2.3–21.2]; p = 0.03) than women with posterior pain only, as did women with combined pubic symphysis and posterior PPGP (n = 268; AOR (pain) 16.5 [1.8–31.1]; p < 0.001) [29]. Kovacs et al. [4] found women who had had instrument-assisted birth (n = 1164; OR 1.9 [1.4–2.6]; p < 0.0001) or epidural in previous birth (n = 1164; OR 1.5 [1.2–2]; p = 0.004) to be more likely to have PPGP. Disability in early pregnancy was a predictor of PPGP-related disability in the third trimester (n = 268; AOR 0.5 [0.3–0.6]; p < 0.001) [29]. Albert et al. [24] found that a history of back trauma was positively associated (n = 2224; AOR 2.8; p < 0.001) with all subgroups of PPGP except symphysiolysis (n = 1771; p > 0.05).

High-impact exercise pre-pregnancy reduced the risk of PGS (n = 12,964; Adjusted Risk Ratio (ARR) 0.8 [0.7–0.9]; p = 0.0005) [43] and Kovacs et al. [4] found that women who engaged in moderate activity were less likely to have PPGP (n = 582; OR 0.7 [0.5–0.9]; p = 0.02). Gjestland et al. [26] also found that women who exercised less than once a week were more likely to have PPGP (n = 1575; AOR 0.8 [0.6–1.0]; p = 0.01) when compared to women who exercised three or more times per week; however, the relation between pre-pregnancy exercise frequency and risk of PGS appears to be non-linear with a frequency of 3–5 times/week most likely to reduce the risk of PGS (n = 17,349; ARR 0.8 [0.8–0.9]; p = 0.003) [43]. While hormonal contraception was not a risk factor [24, 28], progestin intrauterine device use in the year before pregnancy was associated with an increased risk of PGS (n = 34,457; AOR 1.2 [1.1–1.3]; p < 0.001) in multiparous women [28]. Women who experienced nausea (n = 4020; AOR 1.9 [1.8–2.1]; p < 0.0001) and/or vomiting (n = 3946; AOR 2.3 [2.1–2.4]; p < 0.0001) in early pregnancy were more at risk of PGS [31]. Weight increase during pregnancy, years since last pregnancy, salpingitis in the previous year, having had a hormone induced pregnancy (n = 2224; p > 0.05) [24], and number of previous pregnancies (n = 1158; p > 0.05) [4] were not associated with PPGP. Childhood physical abuse was a risk factor for sacral pain during pregnancy (n = 142; AOR 4.4 [1.7–11.4]; p = 0.002) [32].

For psychological factors, depression (n = 1158; β coefficient 0.07 [0.04–0.1]; p < 0.001) and anxiety (n = 1149; p < 0.01) were associated with an increased risk of PPGP in univariate analysis [4]. Women with higher daily stress levels were more likely to have PGS (n = 2224; AOR 1.1; p < 0.001) and one-sided sacroiliac syndrome (n = 1961; AOR 1.1; p < 0.05), but not symphysiolysis (n = 1771; p > 0.05) or double-sided sacroiliac syndrome (n = 1914; p > 0.05) [24]. Higher emotional distress was also linked to an increased risk of PGS (n = 41,070; AOR 2.0 [1.8–2.3]; p < 0.00001) [25].

For socio-demographic factors, being in work (not defined) was associated with a decreased risk of PPGP (n = 1139; OR 0.8 [0.6–1.0]; p = 0.03) [4], and having had no vocational or professional education led to an increased risk of one-sided sacroiliac syndrome (n = 1961; AOR 0.5; p < 0.05) but was not associated with any other PPGP sub-outcome [24].

Risk factors for PPGP in any trimester of pregnancy/trimester not specified examined in one study

Ten studies examined 48 physical factors, 29 socio-demographic factors, and one psychological factor in relationship to PPGP in any trimester of pregnancy (Table 6). Findings are also provided in extended tabular format in additional file 4.

Table 6 Risk factor for PPGP in any trimester/trimester not specified examined in only one study
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Table 7 Recommendation for future research
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Low back pain during pregnancy (n = 2853; β coefficient 0.514; p < 0.001) or having a history of untreated low back pain (n = 1516; OR 1.5 [1.1–2.0]; p = 0.01) was positively associated with PPGP [33, 40], but having received past treatment for low back pain from a doctor (n = 869; OR 1.6 [1.0–2.8]; p = 0.07), chiropractor (n = 1009; OR 0.8 [0.6–1.1]; p = 0.2) or physiotherapist (n = 1163; OR 0.8 [0.6–1.1]; p = 0.2) was not associated with PPGP [40]. Low back pain (n = 306; RR 3.5 [1.7–6.8]; p = 0.0004) or pelvic girdle pain (n = 306; RR 4.7 [1.8–11.8]; p = 0.001) in the year before pregnancy were also positively associated with moderate to severe PPGP [35], and a history of back, bone or joint disease (n = 1516; OR 2.4 [1.6–3.5]; p < 0.0001) or previous lower abdominal pain (n = 1516; AOR 3.1 [1.9–5.15]; p < 0.01) were associated with PPGP [40]. Women who had PPGP in their first pregnancy were more likely to have PPGP in their second pregnancy (n = 682; RR 57.3 [14.5–81.2]) [37], but the time since the first birth was not associated with PPGP (n = 1861; AOR 0.9 [0.8–1.0]) [37]. Lifting heavy loads (n = 3284; OR 1.3 [1.0–1.7]; p = 0.04), having to carry heavy loads (n = 1516; OR 1.9 [1.4–2.6]; p < 0.0001), bending forward (n = 3062; β coefficient 0.05; p < 0.05), twisting and bending at work (n = 3062; β coefficient 0.039; p < 0.05), working in uncomfortable positions (n = 1516; AOR 1.7 [1.1–2.5]; p < 0.05), working in a draft/cold (n = 1516; AOR 2.1 [1.4–3.1]; p = 0.01), and combined oral contraceptive (n = 1684; AOR 1.7 [1.2–2.3]) all carried increased risk of PPGP [33, 37, 38, 47], but strain at work (n = 3062; β coefficient 0.045; p > 0.05), having more than 10 steps of stairs at work (n = 1516; OR 1.1 [0.8–1.4]; p = 0.6), or working with chemicals (n = 1516; 1.1 [0.7–1.6]; p = 0.7) did not carry greater risk [33, 40]. Women who drank four or more cups of coffee daily were also more likely to report PPGP (n = 3286; OR 1.8 [1.3–2.4]; p = 0.0001) [38], and mild pre-eclampsia (n = 81,142; OR 2.2 [1.2–4.0]; p = 0.01), diabetes mellitus (n = 81,142; OR 1.8 [1.1–3.0]; p = 0.02) and gestational diabetes (n = 81,142; OR 1.8 [1.0–3.2]; p = 0.03) were positively associated with symphysiolysis [42]. Previous caesarean section (n = 81,142; OR 0.8 [0.5–1.3]; p = 0.4), recurrent abortion (n = 81,142; OR 1.4 [0.8–2.5]; p = 0.3), severe pre-eclampsia (n = 81,142; OR 0.5 [0.07–3.9]; p = 0.5), chronic hypertension (n = 81,142; OR 1.1 [0.4–3.6]; p = 0.8), pregestational diabetes mellitus (n = 81,142; OR 1.6 [0.5–5.15]; p = 0.4) and premature rupture of membranes (n = 81,142; OR 1.0 [0.6–1.8]; p = 0.9) were not associated with symphysiolysis [42]. Women who exercised once a week (n = 1516; AOR 0.6 [0.4–0.9]; p < 0.01) [40] or exercised at least two to three times a week before pregnancy (n = 306; OR 0.6 [0.3–0.9]; p = 0.02) [35] were less likely to have PPGP. There was no association between the number of pregnancies and PPGP [34].

For socio-demographic factors, there was no association between PPGP and level of influence on work pace control (n = 3272; OR 0.9 [0.7–1.2]; p = 0.6), number of paid working hours (n = 3168; OR 0.7 [0.4–1]; p = 0.08), having a fixed salary (n = 1516; OR 1.1 [0.3–5.1]; p = 0.9), or whether jobs involved manual work (n = 3273; OR 1.1 [0.9–1.4]; p = 0.3), video display terminals (n = 3187; OR 0.8 [0.6–1.1]; p = 0.1), part-time work (n = 1516; OR 1.0 [0.7–1.4]; p = 1.0), shift work (n = 1516; OR 0.8 [0.5–1.2]; p = 0.2) or monotonous work (n = 1516; OR 1.2 [0.8–1.8]; p = 0.4) [38, 40, 41]. However, women who had more influence on breaks at work were less likely to report PPGP (n = 3272; OR 0.7 [0.5–0.9]; p = 0.002) [38] and women who were permanently employed (n = 1737; β coefficient 0.102; p < 0.05) or economically dependent (n = 3062; β coefficient 0.052; p < 0.05) were more likely to report PPGP [33]. Women who were from Pakistani background (compared to Norwegian women) were less likely to have PPGP (n = 137; OR 0.4 [0.2–0.8]) [39] and women who had children already at home were also more likely to have PPGP (n = 1516; OR 2.2 [1.6–3.1]; p < 0.0001), but having more than three rooms in the house (n = 1516; OR 1.4 [1.0–2.2]; p = 0.08), having stairs (n = 1516; OR 0.9 [0.6–1.1] p = 0.2) or a lift at home (n = 1516; OR 0.6 [0.3–1.3]; p = 0.2), living with a partner (n = 1516; OR 0.6 [0.4–1.0]; p = 0.07), or doing more than half of the housework (n = 1516; OR 1.2 [0.9–1.6]; p = 0.3) did not impact on PPGP [40]. Women whose partner had primary or secondary level education were more likely to have PPGP than women whose partner had a university qualification (n = 1822; OR 1.4 [1.1–1.9]; p = 0.02) [38], but the number of years of education women had was not associated with PPGP (n = 1861; 10–12 years AOR 1.0 [0.7–1.3]; 13–15 years AOR 0.9 [0.7–1.3]; ≥16 years AOR 1.1 [0.7–1.7] (versus 7–9 years)) [37].

Depression during pregnancy was associated with PPGP and pubic symphysis pain during pregnancy (Adjusted Risk Ratio 2.74 [1.38–5.44]; p = 0.004) [34].

Discussion

This review represents a comprehensive overview of the available evidence on risk factors for PPGP. A very large number of factors, 148 in total, were examined in 24 studies, yet only 14 factors were examined in more than one study. Definitions of PPGP varied across studies and only three studies included a physical examination despite it being recommended to differentiate PPGP from low back pain [1]. There is an urgent need for consistency in PPGP measurement to allow pooling of data in future systematic reviews. We recommend adhering to the definition of PGP outlined in the European Guidelines and including a physical examination as per the guidelines [1].

Based on the findings of this scoping review, we recommend that systematic reviews are performed on factors that were examined in multiple studies, in particular the factors age, BMI, parity, and smoking, which have been examined in more than five studies. This scoping review can also provide a basis to design robust prospective observational studies to increase our understanding of the development of PPGP. Considering the susceptibility of observational research to bias, repetition of studies is required to draw strong conclusions. This is currently lacking for most of the risk factors examined in the literature, making pooling of multiple studies impossible. Issues to consider include the consistency of the association across studies, and, if present, the strength and timing of the association, and the dose-response relation where appropriate. Such research can provide strategies to improve management of this common condition. This is particularly important given the clinical implications of persistent PPGP, which causes new mothers considerable pain and difficulty, sometimes for up to two years postpartum [48, 49]. Other concerns in some existing studies that should, where possible, be avoided in future are: small sample sizes, a lack of robust multivariable analysis, and incomplete reporting (of the response rate, assessment procedure, the findings and analysis). Prospective registration of observational studies would also help address some of these issues. Recommendations for future research are summarised in Table 7.

Limitations

We conducted a scoping review of the literature on risk factors for PPGP and thus did not conduct a risk of bias assessment. Ideally, this study will be followed by systematic reviews on specific, potential risk factors that have been examined in more than one study to include a risk of bias assessment before synthesising the literature.

Conclusions

This scoping review presents an overview of current literature on risk factors for PPGP. A total of 148 factors were examined in the included studies, but issues of varying definitions and measurement methods, and a lack of replication were identified, which makes meta-analysis impossible. This review provides a basis to guide future systematic reviews and research on the development of PPGP. In conclusion, the literature on risk factors for PPGP is incomplete and statements regarding such risk factors should reflect current limitations and uncertainty.