Back pain in in-vitro fertilized and spontaneous pregnancies

The influence of ovarian stimulation in in-vitro fertilization (IVF) on theprevalence of back pain with onset during pregnancy was studied in 31 womenwho became pregnant after IVF treatment and compared with that of 200spontaneously pregnant women. A two times higher prevalence rate of sacralpain in late pregnancy was reported among IVF pregnant women (P <0.0001), as well as a significantly higher prevalence rate of positiveresults of pelvic pain provocation tests performed in late pregnancy(0.0001 < or = P < or = 0.015), as compared with that of thespontaneously pregnant women. Among the IVF pregnant women, there was asignificant positive correlation between relaxin concentrations in earlypregnancy and the outcome of pelvic pain provocation tests (0.44 < or =r < or = 0.51, P < 0.05). In addition, the serum relaxinconcentration was the factor that best explained differences in sacral painprevalence. When the influence of serum relaxin concentration on back painprevalence was taken into account, women carrying multiple pregnancies hadno more pain than women carrying singletons, and IVF pregnant women had nomore pain than spontaneously pregnant women. These results support thehypothesis that relaxin is involved in the generation of pelvic pain inpregnant women.