Incidence, Clinical Characteristics, and Underreporting of Low Back Pain in Physically Active Pregnant Women: Prospective Cohort Study

Background and Objectives: Low back pain (LBP) is one of the most frequent complications during pregnancy, with a high and variable incidence. LBP has been associated with physical inactivity, but it has not been evaluated exclusively in physically active (PA) pregnant women. This study aimed T to estimate the incidence of LBP in PA pregnant women and describe its clinical, functional, emotional, and occupational impact. Materials and Methods: A prospective cohort of 147 women with PA pregnancies was recruited between gestational weeks 11 and 13+6. Most (92.5%) hold a university degree. All received standardized informational intervention based on international recommendations on PA during pregnancy and LBP prevention. Data were collected through an in-person interview in the first trimester and a postpartum follow-up phone interview. PA was assessed using the International Physical Activity Questionnaire (IPAQ, short version), and LBP intensity was evaluated using the Visual Analog Scale (VAS). Results: LBP occurred in 64.6% of participants, despite maintaining regular PA. Pain intensity was higher in standing position (VAS = 4.9) and lower in lateral decubitus (VAS = 2.7). More than half (55.8%) did not seek medical consultation. LBP was associated with functional limitations (work, sleep, walking), emotional distress (52.6%), and work leave (30.5%; mean 9.4 weeks). In the multivariable logistic regression analysis, standing occupational position showed a borderline association with LBP (OR = 2.14; 95% CI: 1.00–4.55; p = 0.047), while a history of LBP in a previous pregnancy showed a statistically significant association (OR = 2.89; 95% CI: 1.12–7.48; p = 0.029). Higher PA levels during pregnancy were associated with slightly lower odds of LBP (OR = 0.91 per 500 MET·min/week; 95% CI: 0.83–0.99; p = 0.032), although the magnitude of this association was small. Conclusions: LBP showed a high incidence even among PA and highly educated pregnant women. More than half of the women did not seek medical consultation, suggesting potential under-recognition of LBP. Standing occupational position and a previous pregnancy-related LBP were identified as independent risk factors associated with LBP in the multivariable model. Higher PA levels were inversely associated with LBP.