1. Introduction
Low back pain (LBP) is defined as pain or discomfort located between the twelfth rib and the gluteal fold [
1,
2]. During pregnancy, gestational LBP is characterized either by ascending pain from the lumbar region or by pelvic/sacroiliac pain located at the lateral aspect of the fifth lumbar vertebra and extending distally. In some cases, it may be present as a combination of both musculoskeletal dysfunctions [
3]. Pregnancy is associated with anatomical and physiological changes, and LBP is a recurrent event. The etiology of this condition during pregnancy remains unclear and is generally considered to be complex and multifactorial, involving biomechanical, vascular, and hormonal changes [
4].
LBP is one of the most common musculoskeletal dysfunctions during pregnancy and has a significant impact on quality of life, healthcare costs, and productivity [
5]. Reported prevalence during pregnancy ranges from 25% to 90%, with data indicating that approximately 50% of pregnant women experience gestational low back pain. Of these, 80% report that the pain interferes with their daily life activities (DLAs), and 10% are unable to perform their occupational tasks [
5]. While LBP can be present from the first trimester, studies suggest that discomfort peaks during the third trimester [
5,
6]. Musculoskeletal structures seem to adapt their function in response to progressive uterine growth and hormonal fluctuations (e.g., relaxin). These are associated with an anterior shift in the center of mass in pregnant women and increased kinematic forces on the lumbar spine, thereby limiting postural adjustments [
5,
7].
According to the World Health Organization [
8,
9], PA is defined as any bodily movement produced by skeletal muscles that requires energy expenditure, including PA performed during work, play, household chores, travel, and recreational activities. Guidelines from the American College of Sports Medicine [
9] and Canadian recommendations for PA during pregnancy [
10] advise that pregnant women engage in at least 150 min of moderate-intensity physical activity per week. These recommendations also encourage sedentary women to begin PA during the preconception period. Regular PA during pregnancy is associated with maternal and fetal health and presents minimal risks [
4]. Benefits have been associated with reduced risk of maternal complications such as gestational diabetes, hypertensive disorders, preeclampsia, postpartum depression, excessive weight gain, and postpartum weight retention [
4,
5,
10] as well as improvements in overall functional status.
While PA is widely recommended during pregnancy, the evidence regarding its relationship with LBP remains inconsistent. Light- to moderate-intensity PA has been associated in some studies with improved functional capacity and reduced pain perception, whereas others report no clear association or even adverse effects when physical demands are prolonged or repetitive. In particular, sedentary behavior and sustained postures, frequently related to occupational activities, have been linked to increased musculoskeletal discomfort, including lower back pain.
Previous research conducted in Portugal has generally highlighted the relevance of examining how these activity patterns are associated with LBP-related functional disability [
5].
Over the years, pregnancy has often been described as a “window of opportunity” for behavioral change and adoption of health-promoting practices, potentially optimizing the health status of both mother and baby. Commonly referred to as “a teachable moment,” it is characterized by increased individual motivation to modify risk behaviors. Improvements in these habits, during pregnancy, may lead to the adoption of healthier practices maintained into the postpartum period and may be associated with long-term health benefits, including for future pregnancies [
11].
According to previous literature, the severity of LBP tends to be higher in later trimesters and represents one of the leading causes of work absenteeism and one of the most common musculoskeletal complaints among pregnant women [
12]. LBP is also described as the fifth most frequent cause of emergency medical visits and is associated with a significant negative financial impact nowadays. Most women perceive the functional severity of LBP as a natural part of pregnancy and do not adopt preventive or corrective measures [
12]. Current literature shows that individual factors influence not only PA levels but also the functional severity of LBP during pregnancy. Factors such as age, parity, educational level, gestational age, and pre-pregnancy body mass index (BMI) have been analyzed in several studies, demonstrating potential associations with PA levels and the characterization of LBP in pregnant women [
13,
14,
15]. It is important to note that the distinction between different types of activity, such as domestic activities, occupational activities, and structured exercises, is often insufficiently addressed, with most studies focusing primarily on activity intensity. These activity domains may involve distinct biomechanical loads and postural demands, which have been discussed in the literature as potentially relevant for the severity of LBP during pregnancy. Domestic and occupational activities, although predominantly low intensity, may include prolonged standing, bending, or maintaining static positions, which have been associated with increased load on the spine during pregnancy.
However, studies conducted in Portugal remain scarce in addressing the relationship between PA levels and the severity of LBP during pregnancy. Moreover, few studies have simultaneously analyzed both PA intensity and PA type, which limit the understanding of their combined association on pain-related functional disability. This gap highlights the need for more comprehensive approaches that consider both dimensions when characterizing PA patterns in pregnant women.
Thus, this study aimed to examine the association between PA levels and types and LBP related functional disability in pregnant women, allowing for a more comprehensive characterization of activity patterns and their potential relationship with musculoskeletal health during pregnancy.
4. Discussion
The primary objective of this study was to examine PA levels and types among Portuguese pregnant women as well as the associations between PA practice and the severity of LBP during pregnancy.
The results indicate that PA patterns during pregnancy were associated with LBP related functional disability. Most pregnant women concentrated their energy expenditure in light-intensity activities, followed by sedentary activities, predominantly related to domestic and occupational tasks, which constituted the main sources of overall physical activity. These findings are generally consistent with previous studies [
14,
25,
26,
27]; however, given the cross-sectional design, it is not possible to determine the direction of this association, and it remains unclear whether higher disability is associated with increased sedentary behavior or whether greater sedentary behavior is associated with higher perceived disability. These findings should be interpreted with caution. In contrast, low engagement in sports related PA was observed, with a tendency toward reduced participation across gestational trimesters. Previous literature has similarly documented a decline in PA as pregnancy progresses [
14,
25,
26,
28]. However, given the cross-sectional design, these interpretations should be regarded as hypothetical, as the present study did not directly assess these factors.
Low participation in structured or sports-related activities may reflect several factors described in the literature, including the absence of structured exercise programs, perceived functional limitations, and misconceptions regarding the safety of more intense PA during pregnancy. Inconsistent or insufficient guidance from health professionals, particularly during the third trimester, has also been suggested as a possible contributing factor [
16,
25,
26]. These explanations remain hypothetical within the context of the present study and warrant further investigation using longitudinal or qualitative approaches.
This study suggests that greater functional disability during pregnancy was weakly associated with higher levels of sedentary behavior and physical inactivity. Although these associations reached statistical significance, their magnitude was small; therefore, their clinical relevance remains uncertain. These findings should be interpreted with caution and considered exploratory in nature. The literature suggests that light PA contributes to lower daily metabolic expenditure [
5,
26,
27,
29], which may be insufficient to support optimal physical function during a period characterized by marked physiological and biomechanical changes [
30].
Previous studies have reported that LBP prevalence and severity tend to peak during the third trimester and is a risk factor for postpartum continuation (approximately 40%) [
31]. However, these findings should be interpreted with caution as the cross-sectional nature of the data precludes conclusions regarding progression or causality. Factors such as kinesiophobia, pain-related avoidance, fatigue, nausea, sleep disturbances, and lack of access to updated exercise protocols are frequently cited in the literature as potential contributors to lower PA levels during pregnancy [
5,
29,
31,
32,
33]. However, these factors cannot be directly examined within the present study and are therefore presented as hypothesized explanations only.
Another finding was the association between gestational age and the functional disability index, indicating that higher gestational age was associated with higher disability scores. Given the borderline statistical significance of this association, these findings should be interpreted with caution. Nevertheless, this finding is consistent with previous studies [
12,
31]. Prior researches [
5,
31] argue that pre-pregnancy LBP and PA conditions during pregnancy are strong predictors for LBP development, with better functional status being associated with a lower incidence of LBP during pregnancy [
34]. These contrasting findings highlight the complexity of parity-related patterns and suggest that individual and contextual factors may play an important role.
Norsyam et al. [
12] further report that nulliparous women tend to experience more LBP compared to multiparous women, which may help explain the findings of the present study. The authors suggest that individual inexperience with biomechanical and hormonal changes, as well as subjective pain perception—potentially leading to an overestimation of discomfort—and the lower parental burden faced by nulliparous women compared to multiparous women, contribute to this paradoxical finding. However, the same study proposes that LBP is more disabling among multiparous women due to circadian rhythm alterations, decreased lumbopelvic mobility, and significant mechanical and structural changes in the abdominal core [
12,
27].
The sample in this study showed high levels of energy expenditure in occupational activities. Previous research suggests that less physically demanding job roles tend to remain unchanged during pregnancy compared to more demanding occupations. The influence of the “nesting effect” [
5] is identified as a factor in the reduction of more strenuous PA, reinforcing the tendency toward low-energy domestic tasks associated with preparing for a new baby. However, current economic and social realities seem to influence the continued active participation of pregnant women in the workforce to maintain their financial independence and social status [
26]. Nevertheless, these explanations are derived from previous literature and cannot be confirmed within the present cross-sectional design. Thus, they should be viewed as contextual considerations rather than established causal pathways.
According to other authors [
14,
25], women with higher occupational activity tend to have fewer children, whereas women with greater number of children tend to engage less in sports-related PA. A study published in 2025 reports that employed women have a 57.9% lower risk of sedentary behavior compared to unemployed pregnant women. Moreover, women with two or more children are nine times more likely to reach moderate-intensity PA levels, suggesting that parental responsibilities may be a key factor driving PA, as women are traditionally viewed as the primary family caregivers [
26].
Studies also emphasize the importance of PA in general for health benefits; however, in cases of neuromusculoskeletal conditions such as LBP, a more structured and specific exercise plan, encompassing sports PA, may be beneficial. Pregnant women with LBP may benefit from guided exercise programs that include re-education and strengthening of lumbopelvic stabilizers. Core stability exercises have proven effective in controlling functional severity caused by LBP during pregnancy [
35,
36,
37,
38].
It was also noted that pregnant women with higher educational levels tend to exhibit higher sedentary behavior levels, although these findings partly diverge from those of previous researchers [
3,
26], where primiparous women with higher education more frequently met recommended PA levels. These results may relate to the current predominantly sedentary nature of many occupations and individual difficulties in prioritizing leisure time [
39]. Although this finding should be interpreted with caution, as the data do not allow differentiation between discretionary sedentary time and sedentary behavior accumulated during occupational tasks. Given that most participants of the sample were employed and that higher educational achievement is commonly associated with office-based or cognitively demanding professions, the observed pattern may primarily reflect increased occupational sitting rather than lower engagement in PA overall. This interpretation is further supported by the lack of a significant association between educational level and total PA volume [
39]. Thus, higher sedentary time among more educated women should not be assumed to indicate poorer health behaviors, but rather differences in work-related activity profiles during pregnancy.
Contrary to expected patterns, pregnant women with higher pre-pregnancy BMI exhibited similarly elevated levels of vigorous PA. This finding contrasts with the results reported by Bernardo et al. [
13], who reported that higher pre-pregnancy BMI is associated with lower PA indices during pregnancy. This discrepancy may reflect contextual or behavioral factors not accounted for in the present study. Other studies have documented extremely low levels of vigorous activity in this specific population [
25,
26,
28,
40]. However, this result may be explained by Bernardo & Carvalho et al., who highlight the existence of external motivation for pregnant women to control weight gain and/or professional health monitoring that promotes physical activity practice [
28]. Nevertheless, this result should be interpreted with caution due to the small contribution of vigorous activity to total PA and the self-reported nature of the data.
These findings highlight the importance of considering social stigma and perceived barriers such as fatigue, lack of time, and discomfort, which have been described in literature as obstacles to PA during pregnancy. Pregnancy has been described in the literature as a potential opportunity for addressing inactivity-related behaviors, rather than as a condition necessarily requiring restriction [
13]. Low counseling and literacy among pregnant women, combined with fears regarding potential risks inherent in physical activity, contribute to abandonment or refusal to initiate such practices. Thus, a comprehensive analysis of the effect of PA on musculoskeletal pain control is essential, with strong public health implications [
40]. However, the present study was not designed to evaluate the effects of specific interventions.
This study has several limitations that should be acknowledged. The cross-sectional design precludes any inference of causality or temporal relationships between PA patterns and LBP-related disability. Both PA and disability were assessed through self-reported questionnaires (PPAQ and ODI), which, although valid and reliable, remain subject to recall and social desirability biases. The absence of objective assessments of PA and clinical confirmation of LBP may also have influenced the accuracy of the reported measures. Furthermore, the sampling frame is limited to specific regions and healthcare centers and may restrict the generalizability of the findings to the overall population of pregnant women in Portugal. In addition, multiple bivariate analyses were performed, increasing the likelihood of type I errors. The generally modest strength of observed associations further indicates that the results should be considered exploratory and highlights the need for longitudinal and interventional studies to better clarify these relationships. Given that all analyses are unadjusted and cross-sectional, causality cannot be inferred, the potential impact of residual confounding remains, and the findings should, thus, be interpreted with appropriate caution.
The low levels of PA observed in this sample, together with higher disability scores, reinforce the relevance of further research addressing PA patterns and musculoskeletal symptoms during pregnancy. Implementing prevention and education policies within this community to promote increased PA practice may reduce the incidence of such dysfunction.