Furthermore, it is essential to point out that maternal distress may often be associated with specific changes in brain morphology and abnormalities in the functioning of the central nervous system
[4][5]. These specific changes in brain function and morphology lead to vulnerable early development of the human individual, which is re-percussed on later development as well. Maternal prenatal distress affects the outcome of the pregnancy and results in early programming of fetal brain functions with permanent changes in neuroendocrine regulation and offspring behavior
[6][7]. The impact of maternal distress during pregnancy on fetal outcomes and child cardio-metabolic, respiratory, atopic, and neurodevelopment-related health outcomes is also well documented
[8]. Generally observed, the underlying risk factors caused by maternal distress are associated with various aspects of further child development, such as cognition, speech-language development, motor development, behavioral and learning difficulties, socio-emotional development, and neurodevelopmental disorders
[9][10][11][12].
2. Cognition
Cognitive development is a complex mental process based on the ability of the comprehension and process information. The lower mental development of children might be affected by mothers’ prenatal exposure to distress. Several studies found that women exposed to stressful life events such as natural disasters as well as prenatal distress had a significantly increased risk of children with poorer cognitive development at different ages
[13][14][15][16]. Trait anxiety in the second trimester and both trait and state anxiety at 32 gestation weeks predicted lower mental developmental scores in children aged 8 and 24 months
[13][14]. Elevated maternal cortisol levels in late pregnancy were associated with lower mental development in children aged 3 months
[14]. Unlike previous studies, the study of Keim et al.
[17] indicates that pregnancy-specific anxiety very poorly correlates with overall mental development at 12 months of age.
Studies dealt with the influence of maternal distress during pregnancy on language development as well as language skills such as reading, spelling, writing, and mathematics skills (numeracy), most often comparing the impact of mothers’ distress on the development of receptive and expressive language in children. Research findings pointed to lower productive language abilities and receptive language in toddlers aged 30 months who were prenatally exposed to maternal distress
[15]. On the contrary, a study conducted by Keim et al.
[17], in which the association between prenatal and postnatal anxiety, stress, and depressive symptoms on language ability of 12-month-old infants was examined, pointed to better language skills in children whose mothers had higher depression symptoms. The impact of prenatal maternal distress on specific learning abilities (literacy and numeracy) in children aged 10 was examined in a large population follow-up study
[18]. This study pointed to the significant difference between genders: girls had lower accomplishments in reading, while no association was found between prenatal distress and spelling, writing, and numeracy, compared to boys whose mothers experienced maternal distress. On the other hand, boys whose mothers had three or more stressful events during pregnancy had higher scores on numeracy and writing test compared to boys from the control group.
3. Socio-Emotional Development
Socio-emotional development is a complex process that involves the interaction of maturation factors and the child’s environment. Some studies reported an association between maternal distress during pregnancy and postpartum and poorer socio-emotional development
[19][20][21]. Further, a small study of mother-infant dyads
[5] used diffusion tensor imaging (DTI) pointed out the association between the internalizing domain of behavior and neonatal insula variation in infants whose mothers had prenatal distress.
Numerous studies have described the impact of maternal distress on various aspects of temperament
[16][22][23]. Infants between 16–18 months whose mothers experienced more stressful life events during early pregnancy (first trimester) had low regularity, persistence, and attention span
[16]. Likewise, pregnancy-specific anxiety was a positive predictor for 6-months-old infant fearfulness and falling reactivity
[22], while infants whose mothers were exposed to higher levels of distress during the first trimester of pregnancy (illness/infection conditions, older mothers, subject distress) were found less responsive
[24]. Furthermore, at six months of age, pregnancy-related anxiety can be a predictor of mood disturbance
[1].
Trait anxiety in late pregnancy predicts a more difficult temperament in infants, while state anxiety and pregnancy-related anxiety had no significant effect on temperament
[25].
Few studies tried to determine whether mothers’ distress during pregnancy predicts the value of mother-infant bonding postpartum. During the COVID–19 pandemic, the study examined mother-infant dyads for 3 months, and the results showed that lower levels of maternal anxiety at delivery are correlated with higher mother-infant bonding. On the other hand, in another study, a positive correlation was found between prenatal pregnancy anxiety, postpartum trait anxiety, postpartum depression, and postpartum bonding, but a significant association was found between pregnancy-related fear, postnatal anxiety, and mother-infant bonding
[26]. One particular study examined the multimodal processing of face and voice pairs regarding fearful and happy emotions in 9-month-old infants
[27]. The authors hypothesized that non-typical experiences, such as mothers’ distress during fetal development, can alter the development of this ability, and the results of the study showed that general anxiety, but not state anxiety, had significant effects on the processing of emotional information.
4. Fine and Gross Motor Development
Motor development involves the development of two aspects of motor skills: fine and gross motor skills. Studies assessing infants’ motor development at 24–30 months
[19] and 36 months of age
[28] indicated that high prenatal maternal anxiety was associated with poorer gross motor development related to delays in fine and gross motor development and problem-solving domains.
Furthermore, fine and gross motor development was assessed in children at 2, 6, and 16 months
[12]; 10 months
[29]; and 12 and 24 months
[13]. At 2 months, fine and gross motor skills were positively correlated with maternal peritraumatic distress levels. However, at 6 months, fine and gross motor skills were negatively correlated with maternal distress. No significant association was found between fine gross motor functioning and maternal distress at 16 months of age, while gross motor skills were negatively correlated with maternal distress
[12]. Further, at 10 months of age negative correlation was found between maternal trait anxiety and fine motor skills, while no significant correlation was found between maternal anxiety and gross motor skills, visuomotor function, and brain stem function
[29]. Moreover, at the ages of 12 and 24 months, the motor development of infants who were exposed to maternal distress during pregnancy was observed within the overall development
[13]. This study’s results indicated lower scores on the motor scale in infants exposed to higher maternal distress at the ages of 12 and 24 months.
The longitudinal study assessed the effects of objective and subjective prenatal maternal stress of pregnant women exposed to a natural disaster on the motor development of 5½ years old children and showed a correlation between prenatal maternal stress and bilateral coordination and visual-motor integration
[30]. Finally, the study investigated the long-term effects of the number and timing of stressors experienced during pregnancy on motor development at 10-, 14- and 17-years old children
[31] and indicated that children whose mothers had more than three distressing events during pregnancy had lower motor competence at all tested ages. This result implicated that number of experienced prenatal stresses may have a cumulative effect on offspring motor development.
5. Neurodevelopmental Disorders
The most frequent neurodevelopmental disorders, which are characterized by developmental deficits that produce impairments of personal, social, academic, or occupational functioning, are: attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD)
[32]. Several studies have been investigating maternal prepartum and postpartum distress as risk factors for ASD and ADHD
[33][34][35], pointing to the association between prenatal stress and a higher frequency of diagnoses of ASD or ADHD in children after the age of 3. Gender differences (for ADHD diagnosis)
[35] and time of exposure to stress during pregnancy were found to be significant for both ASD (first and third trimester) and ADHD (third trimester)
[34]. Some studies focusing on the symptoms of ASD and ADHD in children whose mothers experienced prenatal distress showed that both boys and girls, not gender-related, at the age of 6 years and 6 months scored higher on autism-like traits, especially when mothers experienced more than one stressful event during pregnancy
[36] while only boys were likely to be at a higher risk for ADHD symptoms
[37]. On the other hand, a study focusing on the diversity of autism symptoms in children already diagnosed with ASD who have been exposed to distress during intrauterine development
[38] found that the symptoms of autism are more severe only in those children whose mothers experienced more than one stressful event during pregnancy. The symptoms were significantly increased in the domain of behavior (repetitive and restricted behavior), communication, and language (syntax, semantics, coherence, and stereotyped language). The obtained results may indicate that prenatal stress can alter ASD phenotype.