Symphyseal distention in relation to serum relaxin levels and pelvic pain in pregnancy

Objective. To elucidate whether there is an association between symphyseal distention, circulating relaxin levels and pelvic pain in pregnancy. Methods. Serum relaxin and symphyseal width were assessed in 19 consecutive referral cases with severe pelvic pain at 35 weeks of pregnancy and in a cohort of 49 women at 12 and 35 weeks of pregnancy. The referral cases were received over a period of two years and four months and the cohort was recruited over a period of two months. Relaxin was measured with an ELISA test and symphyseal width assessed using ultrasonography. All women with pelvic pain were clinically assessed. The women were divided into three groups; Group A (n=38), cohort cases with no or mild pain; Group B (n=11), cohort cases with disabling pain; and Group C (n=19), referral cases. Results At 35 weeks of pregnancy mean symphyseal width was 4.5 mm (s.d. 1.0 mm) in Group A, 5.7 mm (s.d. 2.6 mm) in Group B, and 7.4 mm (s.d. 3.5 mm) in Group C. The difference between Groups A and B is statistically significant (p=0.044) as is that between Groups A and C (p<0.0001). Serum relaxin levels were not associated with symphyseal distention or disabling pain. Conclusion. Severe pelvic pain during pregnancy was strongly associated with an increased symphyseal distention. However, the severity of pain did not predict the degree of symphyseal distention in the individual case, indicating that other mechanisms are also involved. Serum relaxin levels were not associated with the degree of symphyseal distention or with pelvic pain in pregnancy.