Objective
The purpose of this study was to estimate the association of parity with pelvic girdle syndrome (PGS; pain in anterior and bilateral posterior pelvis).
Study Design
We included 75,939 pregnant women in the Norwegian Mother and Child Cohort Study. Data were obtained by self-administered questionnaires.
Results
By pregnancy week 30, 15% of the women had developed PGS. Among first-time mothers, 11% of the women reported PGS, compared with 18% of the women with 1 previous delivery and 21% of women with 2 previous deliveries. The odds ratios for PGS of having had 1 or 2 previous deliveries were 1.9 (95% confidence interval [CI], 1.9–2.0) and 2.4 (95% CI, 2.3–2.6), respectively, after adjustment for other study factors. For PGS with severe pain, the corresponding odds ratios were 2.6 (95% CI, 2.3–2.9) and 3.8 (95% CI, 3.3–4.3).
Conclusion
The risk of the development of PGS increased with number of previous deliveries, which suggests that parity-related factors play a causal role.
Pelvic girdle pain affects 20-45% of all pregnant women. This condition is associated with functional disability and is a major cause of sick leave during pregnancy. Despite an increasing number of studies, the cause and pathogenesis of pelvic girdle pain remain poorly understood. Several potential risk factors that have been investigated include previous low back pain, maternal age, high body mass index (BMI), low educational level, emotional distress, physically demanding work, smoking, and physical activity levels. Contradictory results have been reported on the impact of these factors. However, previous low back pain has been associated consistently with increased risk of pelvic girdle pain in pregnancy.
In some studies, having previously given birth has been identified as a risk factor for pelvic girdle pain in a subsequent pregnancy. However, in other studies, parity had no effect on the risk of pelvic girdle pain. Most previous studies of the association of parity and pelvic girdle pain have had methodologic limitations, such as low statistical power or lack of control for confounding factors.
Reliable knowledge on the impact of parity on pelvic girdle pain may increase our understanding of the cause of this condition. Our aim was to report the occurrence of pain in different locations of the pelvic girdle in a cohort of 75,939 pregnant women. We estimated the association of the number of previous deliveries with the development of pelvic girdle syndrome (PGS), defined as pain in anterior and bilateral posterior pelvis. We also made adjustment for other potential risk factors.
Materials and Methods
Study design, recruitment, and study population
During the years 1999-2008, all pregnant women who were scheduled to give birth at 1 of 50 hospitals in Norway were eligible to be recruited in the Norwegian Mother and Child Cohort Study ( www.fhi.no/morogbarn ) that was conducted by the Norwegian Institute of Public Health. There are a total of 52 hospitals with a maternity ward in Norway. The women were recruited at the routine ultrasound examination in pregnancy week 17. This examination is a part of the public antenatal care program and is offered to all pregnant women free of charge. The Norwegian Mother and Child Cohort Study is described in detail elsewhere. There were no exclusion criteria. The participation rate was 41%; 95% of the participants completed both questionnaires that we used in our data analyses, which left 75,939 women in our study sample.
Data collection and follow-up
Data were obtained by the use of 2 self-administered questionnaires. The first questionnaire was completed in pregnancy week 17 (mean, 17.4 ± 2.8 [SD] weeks) and included questions on sociodemographic factors, general health, and obstetric and gynecologic history. In pregnancy week 30 (mean, 30.6 ± 2.0 weeks), the women answered the second questionnaire, which included questions on health during pregnancy. Both questionnaires were returned by mail.
Study factors
Information on pelvic girdle pain was obtained by the following questions in pregnancy week 30: Do you have pain in the pelvic girdle? If you have pain in the pelvic girdle, where is the pain located? One or more locations could be specified: in the frontal part of the pelvis/on 1 side of the rear part of the pelvis/on both sides of the rear part of the pelvis. Pain intensity was scored as mild or severe at each location. In accordance with previous classifications, pelvic girdle pain was subgrouped into pain in the anterior pelvis, unilateral posterior pelvis, bilateral posterior pelvis, combined anterior and bilateral posterior pelvis, other pelvic location combinations, and no pain. PGS was defined as having combined pain in anterior and bilateral posterior pelvis. In additional analyses, PGS was subdivided according to reported pain intensity; the presence of severe pain in all 3 pelvic locations was deemed to be PGS with severe pain. Functional disability was addressed by “yes/no” answers to the following questions: Do you frequently wake up at night because of pelvic girdle pain? Do you use crutches because of pelvic girdle pain?
Information on all explanatory variables was obtained in pregnancy week 17. Parity was defined as the number of previous pregnancies that lasted >21 weeks and was coded para 0, para 1, para 2, and para ≥3. Maternal age was coded as <25 years, 25-34 years, and ≥35 years. BMI was calculated as weight/height 2 (kilograms per square meter) and was coded as <25, 25-29, ≥30 kg/m 2 , and missing. Educational level was coded as <12 years, 12 years, 13-16 years, ≥17 years, and missing. The presence of emotional distress was measured with the Symptom Checklist–5, which is a short-form of the Hopkins Symptom Checklist. The Symptom Checklist–5 consists of 5 questions about symptoms that are related to anxiety and depression. We defined a mean score ≥2.0 as the presence of emotional distress. Information about previous low back pain was obtained with the answer (no/yes, mild pain/yes, severe pain) to the following question: Have you had low back pain before being pregnant for the first time? Previous low back pain was defined as having had mild or severe low back pain before being pregnant for the first time. Smoking in pregnancy was coded as nonsmoker, occasional smoker, daily smoker, and missing. Having physically demanding work was scored with a 4-point Likert scale for response to the following statement: I perform physically demanding work (agree/agree mostly/do not agree very much/do not at all agree). In the data analysis, physically demanding work was categorized as agree, do not agree, and missing. The physical activity level was based on the following question: How often, during the last 3 months before this pregnancy, were you short of breath and sweating while being physically active? The physical activity level was coded as <1 time weekly, 1-2 times weekly, ≥3 times weekly, and missing.
Statistical methods
The occurrence of pelvic girdle pain in pregnancy is presented as proportions. The associations of the study factors with PGS (pain in the anterior and the bilateral posterior pelvis) were estimated as crude and adjusted odds ratios (aORs) with 95% confidence interval (CI) with logistic regression analyses. Both PGS and PGS with severe pain (severe pain in all 3 pelvic locations) were used as the dependant variable. The SPSS statistical software package (version 15.0; SPSS Inc, Chicago, IL) was used for the statistical analyses.
Ethical considerations
The Norwegian Mother and Child Cohort Study was approved by all Regional Committees for Medical Research Ethics in Norway and by the Norwegian Data Inspectorate. All participants signed an informed consent form.
Results
The mean age of the women was 29.7 years (range, 14–47 years; Table 1 ). Forty-six percent of the women were nulliparous; 36% were primiparous; 15% were segundiparous; and 3.4% were multiparous. The mean BMI was 25.1 ± 4.2 kg/m 2 in pregnancy week 17.
| Characteristic | Percent | Mean ± SD |
|---|---|---|
| Maternal age, y | 29.7 ± 4.6 | |
| Body mass index, kg/m 2 | 25.1 ± 4.2 | |
| Parity, n | ||
| 0 | 46.2 | |
| 1 | 35.7 | |
| 2 | 14.7 | |
| ≥3 | 3.4 | |
| Educational level, y | ||
| <12 | 7.7 | |
| 12 | 27.4 | |
| 13-16 | 39.3 | |
| ≥17 | 20.5 | |
| Missing | 5.1 | |
| Previous low back pain | ||
| No | 80.8 | |
| Yes | 19.2 |
Distribution and intensity of pelvic girdle pain according to pain location
Fifty-eight percent of the women (44,069/75,939) reported pain in ≥1 pelvic location during pregnancy week 30. Severe pain in ≥1 location in the pelvis was reported by 12.6% of all women. PGS was reported by 15% of the women, of whom 17% (2.5% of the total) reported PGS with severe pain ( Table 2 ). Crutches were used by 7.7%, and 15.4% of all women frequently woke up during the night because of pelvic girdle pain.
| Characteristic | Pelvic girdle syndrome, a n (%) | Anterior pain, n (%) | Unilateral posterior pain, n (%) | Bilateral posterior pain, n (%) | Other pain combinations, n (%) | No pelvic girdle pain, n (%) |
|---|---|---|---|---|---|---|
| Pain | 11,414 (15.0) | 9914 (13.1) | 7909 (10.4) | 10,822 (14.3%) | 4010 (5.3) | 31,870 (42.0) |
| Severe pain | 1906 (2.5) | 1165 (1.5) | 884 (1.2) | 1684 (2.2) | 3897 (5.1) | 66,403 (87.4) |
The impact of parity on PGS
Among first-time mothers, 11% of women reported PGS, compared with 18% of women with 1 previous delivery and 21% of women with 2 previous deliveries (crude OR, 1.9; 95% CI, 1.8–2.0 and 2.3; 95% CI, 2.2–2.4, respectively, with first-time mothers as the reference; Table 3 ). The positive association between parity and PGS remained after adjustment for the other study factors. The aOR was 2.0; 95% CI, 1.9–2.1 for primiparous women and 2.6; 95% CI, 2.4–2.7 for segundiparous women, with nulliparous women as the reference. The association with parity was stronger for severe PGS than for PGS without severe pain. Severe PGS was present in 1.4% of first-time mothers, compared with 3.1% of the women with 1 previous delivery and 4.3% of the women with 2 previous deliveries (crude OR, 2.3; 95% CI, 2.1–2.6 and 3.2; 95% CI, 2.9–3.7, respectively). Also for PGS with severe pain, the association with parity remained after adjustment for the other study factors (aOR for primiparous and segundiparous women, 2.6; 95% CI, 2.3–2.9 and 3.8; 95% CI, 3.3–4.3, with nulliparous women as the reference). When any reported pelvic girdle pain was used independent of the location as the outcome variable, the aOR for 1 previous delivery was 1.9; 95% CI, 1.8–1.9 and 2.3; 95% CI, 2.2–2.4 for 2 previous deliveries.
