Nutritional deficiencies or stress during the prenatal period could lead to adverse events for the child, some of which may be life-long, new research suggests.
Researchers from Baylor College of Medicine conducted the study on rats, and found that exposure to stress hormones while in utero stunts foetal muscle growth – an important finding, given that muscles are required for many vital functions, including breathing, feeding and swallowing. Compromise of these important muscles during foetal development would likely affect the growth rate of the new-born infant.
The study, titled “Precocious glucocorticoid exposure reduces skeletal muscle satellite cells in the foetal rat”, confirmed that stress during pregnancy raises glucocorticoid levels. Stress during pregnancy may be from external or internal sources, including adverse environmental conditions, maternal malnutrition, or illness.
These findings correlate with previous studies that identified a relationship between malnutrition in utero, low birth weight, and long-term reduced muscle mass and strength. Malnutrition and stress during pregnancy have previously been proposed as two major factors that affect foetal growth and development. Both factors are known to produce high levels of the glucocorticoid, cortisol.
Excess glucocorticoids, a class of stress hormones synthesized by the adrenal glands, have been shown to cause atrophy and insulin-resistance in adult muscles. There is growing evidence that excess glucocorticoids also exert negative effects on foetal development and post-natal outcomes. Even mild maternal stress levels can cause significant effects on the fetes, which may be life-long, due to the involvement of muscle stem cells.
While glucocorticoids are necessary for normal foetal development, excess exposure while in utero may also have detrimental consequences for vital organs, including the brain, as glucocorticoids activate, regulate, or participate in, many biochemical processes, such as the expression of numerous receptors, enzymes, growth factors, clotting factors, proteins and signalling pathways.
Muscle development during the foetal period is especially important, since skeletal muscle composes up to 50% of body mass, and the amount of muscle fibre is determined before birth – there is zero net increase of muscle fibres after birth. Postnatal muscle growth is facilitated by the addition of more protein and nuclei to the muscle fibres, however the addition of nuclei ceases at puberty. Further muscle growth in adulthood can only occur via the addition of protein to the muscle fibres.
While early overexposure to glucocorticoids during intrauterine development may benefit neonatal viability in the event of a preterm birth, it reduces overall foetal growth and decreases total cell numbers in some tissues. Excess glucocorticoids have also been shown to reduce overall weight and surface area of the placenta, which may affect transplacental transfer of nutrients and other substances. The effects of prenatal overexposure are influenced by gestational age at the time of overexposure.
Synthetic glucocorticoids, up to 20 times more potent than natural glucocorticoids, are commonly administered to women in preterm birth, to prevent respiratory distress in preterm infants. They may also be used during pregnancy to treat asthma, arthritis or adrenal insufficiency.
This study not only highlights the importance of good nutrition and antenatal care for all pregnant mothers, but raises important issues about treating medical conditions in expectant mothers or new-borns with steroids, and the potential consequences of such treatment.
Furthermore, additional research is needed to determine if negative effects on the foetus could potentially be minimised or eliminated via post-natal medical treatment.
