Background: Many women during pregnancy suffer from low back pain (LBP). This pain has a significant effect on women's quality of life.  Fifty percent of women during pregnancy have low back pain. According to the related literature, LBP may be a weakening condition that influences on women's daily activities and their productivity and affecting women's quality of life. LBP must not be neglected and great attention should be given to this complaint.  The aim of the study was to assess the effect of progressive muscle relaxation exercises during pregnancy on low back pain and quality of woman's life. Subjects and Method: Design: A quasi-experimental research design was carried out at Salah Abd-Rabo obstetric and gynecological clinic and Sahala obstetric and gynecologic center, Alexandria, Egypt. Subjects: A convenient sample of 40 pregnant women were assigned randomly to a muscle relaxation group or a control group (20 participants in each group) according to certain criteria. Tools: Three tools of data collection were used: A questionnaire sheet, a visual analog pain intensity scale (VAS) and health related quality of life (HRQOL) questionnaire. Results: There is a significant decrease in pain intensity at 2 months, (p < 0.05) among participants in the study group while, pain intensity increased among control group participants after the same period. In addition, there is a significant improvement in all quality of life aspects after two months among the study group than control group, (p < 0.05).  Conclusion and recommendations: PMR can reduce low back pain among pregnant women and improve their quality of life. Pregnant women who wish to stop pharmacological pain relief should be taught about PMR.