Background: Musculoskeletal changes occur during pregnancy; one-half of pregnant women experienced low back pain and/or pelvic pain during pregnancy. Prescription opioid use for Medicaid enrolled pregnant women has increased dramatically due to severe low back pain/pelvic pain. Objectives: This study aimed to explore the prevalence of low back pain/pelvic pain and related risk factors among a broader population. Design: This is a retrospective cohort study. Methods: This study utilized de-identified Medicaid claims data provided by the South Carolina Revenue and Fiscal Affairs Office, including individuals who gave birth between 2016 and 2021 during pregnancy. Low back pain/pelvic pain and a group of musculoskeletal risk factors were identified with International Classification of Diseases v10. Comparisons were made for the prevalence of low back pain and pelvic pain between those with pregnancy-related musculoskeletal risk and those without. Results: Among 167,396 pregnancies, 65.6% were affected by musculoskeletal risk factors. The overall prevalence of low back pain was 15.6%, and of pregnancy-related pelvic pain was 25.2%. The overall prevalence for either low back pain or pelvic pain was 33.3% (increased from 29.5% in 2016 to 35.3% in 2021), with 24.6% being pregnancy-induced. Pregnancies with musculoskeletal risk factors were more likely to be diagnosed with low back pain (20.7% versus 5.7%, p < 0.001) or pelvic pain (35.3% versus 6.0%, p < 0.001) than those without. Conclusion: This study found a very high prevalence of musculoskeletal risk and a high prevalence of low back pain or pelvic pain, with an increasing trend, among South Carolina pregnancies enrolled in Medicaid during the period 2016–2021. Most of the diagnosed low back pain or pelvic pain were pregnancy induced. Musculoskeletal risk factors were associated with low back pain or pelvic pain.