Prenatal stress (or prenatal maternal stress) is exposure of an expectant mother to psychosocial or physical stress, which can be caused by daily life events or by environmental hardships. This psychosocial or physical stress that the expectant mother is experiencing has an effect on the fetus. According to the Developmental Origins of Health and Disease (DOHaD), a wide range of environmental factors a woman may experience during the perinatal period can contribute to biological impacts and changes in the fetus that then causes health risks later in the child's life.
Health risks include impaired cognitive development, low birth weight, and risk of mental disorders in the offspring.
Conducting Research
Studies have been conducted longitudinally in order to explore the way that prenatal stress impacts the fetus and its development. These studies took place over the course of the pregnancy and months after in order to collect the data necessary. The stress of the mothers was assessed using self-questionnaires like the Perceived Stress Scale (PSS) and the Patient Health Questionnaire-8 (PHQ8).
While focusing on the stress of the mothers during the pregnancy, researchers also focused on the hypothalamic-pituitary adrenal axis (HPA axis) which is a set of glucocorticoid feedback interactions through the mother to the placenta and then to the fetus. By focusing on the HPA axis, researchers can see how prenatal stress affects fetal development.
Some research includes studies like McKenna et al. suggesting that the idea of pregnancy can cause an increased risk of psychopathology and these exposures during gestation impacts epigenetic. The mother's usage of selective serotonin repute inhibitors (SSRIs) was observed while the epigenetic age of the child was calculated through fetal umbilical cord blood.
Saboory et al. found that prenatal psychosocial stress can cause delays in child growth and development through assessing the child's weight, height and head circumference every two months after they were born. They also assessed the child's cognitive development through the use of the Ages and Stages Questionnaire (ASQ).
Another study, Brannigan et al. focused on how prenatal stress contributes to personality disorders by looking at children decades later born from mothers who spent time in a mental health clinic in Finland.
This research all found negative correlations between prenatal stress and the child's development.
Pathway
Stress during the development of the fetus can be inherited and change the gene expression in the fetus. This change is an epigenetic change that modifies but does not affect the building of the DNA sequence. This modification will affect whether the gene is turned off or on and will lead to Transgenerational Stress Inheritance.
One of the pathways that has been studied is the inheritance of disrupted heterochromatin. Heterochromatin is important in many functions of the cell mostly in gene regulation. During high levels of stress during pregnancy dATF-2, which is required for formation of heterochromatin, will phosphorylate and disrupt the formation. This will lead to the release of dATF-2 from the heterochromatin, which then can be inherited in offspring.
Another pathway that prenatal stress can interfere with fetal development is telomere length. A telomere is a structure of repetitive DNA sequences that can be found at the end of chromosomes. They are made up of the same short DNA sequence that is repeated multiple times and serve to protect the ends of chromosomes so they do not become damaged. Another function of telomeres is to allow chromosomes to properly function in the process of replication. However, each time a cell divides, the telomeres loses length and becomes shorter. After repeated replications they will eventually become so short that the cell is unable to divide any further and the cell will die. When offspring are exposed to prenatal distress during development it can affect the length of the offspring's telomeres, more specifically it can result in shortened telomeres. Shortened telomeres have been linked to multiple issues including shortened lifespan and increased risk of diseases. Typically, telomeres shorten substantially with increasing age, and telomere length is thus a bioindicator of aging. However, prenatal stress puts offspring at an increased state of vulnerability by shortening the telomeres and leaving less room for shortening as the offspring continue to age.