Physical activity during pregnancy and baby brain development – The elephant in the consulting room

It is well established that the health behaviors of a woman, such as smoking, alcohol intake and physical activity, whilst pregnant have significant impact on the development of her baby. Over the past three decades, public health interventions have proven largely successful at mitigating many high-risk health behaviors. In 1994, 22% of women in Australia smoked during pregnancy (Mohsin, Bauman, and Forero, 2011); today only 8% smoke at any time during pregnancy and almost a quarter of these discontinued after 20 weeks gestation (Australian Institute of Health and Welfare, 2023). Similarly, while 38% of women in Australia consumed alcohol while pregnant in 2001 (Stanesby, Cook, and Callinan, 2018), today only 3% consume alcohol during the first 20 weeks of gestation, and less than 1% consume alcohol thereafter (Australian Institute of Health and Welfare, 2023). Conversely, public health interventions aimed at increasing physical activity behaviors among pregnant women have been less successful, with most women continuing to either decrease or cease their physical activity altogether during pregnancy (Hayman, Short, and Reaburn, 2016). In fact, research suggests that 70% of pregnant women in Australia do not meet physical activity guidelines (Brown et al., 2022). Just like smoking and alcohol, physical inactivity is associated with adverse pregnancy outcomes – many of which are major risk factors for poor baby brain development. Highlighting the negative impact a particular health behavior has on the health and wellbeing of the fetus has played an integral role in successful public health interventions to date. This approach is supported by research indicating that knowledge of fetal health benefits and adverse outcomes resulting from a health behavior serves as a crucial motivator for adopting positive health behaviors during pregnancy (Edvardsson et al., 2011). This may, in part, explain why physical activity interventions to date may have had limited success, as most of the messaging has focused on the maternal, rather than fetal, health benefits associated with physical activity during pregnancy. With pregnancy documented as a ‘teachable moment’ during which women have increased motivation to undertake healthy lifestyle behaviors that benefit their baby, and the proven effectiveness of messaging targeting fetal health outcomes on improving health behaviors, we suggest that pregnancy physical activity counselling should highlight the benefits of physical activity during pregnancy on baby brain development. Accumulating evidence in pre-clinical models shows physical activity during pregnancy has direct beneficial intergenerational effects on baby brain development (Yang et al., 2021). That is, maternal physical activity during pregnancy enhances offspring brain health via enhancements in brain growth factor expression, neurogenesis and brain structure, which importantly translate into improvements in related neurobehavioral outcomes such as learning, memory, and anxiety (Goli et al., 2021, Yang et al., 2021). Fundamentally, effects seem consistent across all offspring age groups (prenatal-adulthood), indicating that physical activity exerts long-lasting benefits on offspring brain structure and neurobehavior (Yang et al., 2021). While a recent scoping review reveals that little is known about the direct intergenerational effects of maternal physical activity in humans (Valkenborghs, Dent, and Stillman, 2022), we believe sufficient evidence of the indirect pathways through which physical activity during pregnancy may benefit baby brain development exists to merit screening and education of pregnant women (Davenport et al., 2018). For example, the best evidenced risk factors for impaired baby brain development include poor maternal metabolic (e.g., diabetes, obesity) (Camprubi Robles et al., 2015, Tong and Kalish, 2021), cardiovascular (e.g., hypertension, pre-eclampsia) (Sun, Moster, Harmon, and Wilcox, 2020), mental (e.g., stress, depression, anxiety) (Davis et al., 2020, Dean et al., 2018, Polanska et al., 2017), and sleep (Nakahara et al., 2021, Peng et al., 2016) health during pregnancy. While it is worrying that these conditions are highly prevalent during pregnancy (obesity – 23% of pregnancies, gestational diabetes – 16%, gestational hypertension – 3%, mental health – 23%, and disordered sleep – 46%) (Australian Institute of Health and Welfare, 2023, Savory et al., 2021, Sedov et al., 2018), it is promising that they are all modifiable by physical activity during pregnancy (Brown et al., 2022). Furthermore, improvements in these markers of maternal health due to physical activity can have downstream effects on the fetus via enhanced placental vascular function as well as proliferation of trophoblasts and villus volume (Bergmann et al., 2004, Kubler et al., 2022, Son et al., 2019, Zhao et al., 2022) – processes known to be pathologically altered via the aforementioned pregnancy conditions. In summary, many of the pregnancy risk factors for impaired baby brain development are modifiable by physical activity which represents a missed opportunity for a significant modifiable health behavior during a critical period of developmental plasticity. The success of public health interventions targeting behaviors such as smoking and alcohol consumption during pregnancy suggests that the high rates of physical inactivity during pregnancy worldwide should be approached with a comparative scale of corrective action and it is apparent that physical activity messaging needs to illuminate the fetal health benefits. To this end, we conclude that an educational infographic (Fig. 1) on potential benefits for baby brain development will be a useful tool to empower and motivate more pregnant women to be active in accordance with current physical activity guidelines – in the same way that pregnant women alter their diet, as well as stop smoking and consuming alcohol.