Table 2.
Findings of literature review.
| Prenatal factor | N1 | Article N2 | Summary finding | |||
|---|---|---|---|---|---|---|
| 1. | Genetic and biological factors | 1.1. | Genes | |||
| 1.1.1. | Genetic factors (compared Monozygotic and Dizygotic twins) | 1 | 35 | Monozygotic twins were more similar in temperament scores than dizygotic twins, indicating that genetic factors may play a role in temperament. | ||
| 1.1.2. | 5HTT, DRD4, and MAO-A | 2 | 17, 18 | Genes-environment interaction between TaqIA polymorphism, 5-HTTLPR genes, tobacco intake, and prenatal anxiety among mothers was related to higher attention and irritability in the infant. | ||
| 1.2. | Biological factors | |||||
| 1.2.1. | Maternal cortisol (saliva or blood), placental cortisol, Corticotropin-releasing hormone (CRH) or Adrenocorticotropic hormone (ACTH) | 4 | 10, 21, 27, 29 | Most of the studies reported that a significant correlation between increased levels of maternal stress hormone during pregnancy and higher difficult temperament of infants, such as higher emotional activity, higher irritability and fussiness and higher fear and distress feelings. | ||
| 1.2.2. | Fetal heart rate | 1 | 23 | Third trimester foetuses who showed heart rate increases exposed to maternal stress were more likely to exhibit high motor reactivity in response to novelty at 4 months of age. | ||
| 2. | Environmental | 2.1. | Substance use | |||
| factors | 2.1.1. | Smoking | 3 | 18, 20, 25 | Prenatal smoking was associated with lower positive mood and lower reactivity to stimuli, higher attention and irritability among infants. | |
| 2.1.2. | Alcohol (Maternal or Paternal) | 1 | 30 | Infants of an alcoholic father displayed ‘stubborn' and ‘persistent temperaments' at 12 months of age. | ||
| 2.1.3. | Illegal drug | 2 | 5, 24 | Infants of mothers who used cocaine or opiate scored lower on ‘smiling and laughter', or ‘poor attention to stimuli'. | ||
| 3. | Socio-demographic factors | 3.1. | Low income/ethnic minority | 2 | 1, 8 | Prenatal stress caused by stressful events among low income women predicted lower ‘surgency' and ‘regulation' of infants. |
| 3.2. | Maternal nutrition | |||||
| 3.2.1. | Chocolate consumption | 1 | 28 | No significant relationship between chocolate consumption and infant temperament. | ||
| 3.2.2. | Intakes of polyunsaturated fatty acids (PUFAs) (n3, n6) | 1 | 8 | Prenatal stress effects on infant ‘orienting' & ‘regulation' were modified by maternal n3: n6 ratios among African American. | ||
| 4. | Psychological factors | 4.1. | Maternal mental health | |||
| 4.1.1. | Prenatal depression or anxiety among mothers | 9 | 2, 4, 6, 10, 11, 13, 14, 26, 32 | Both prenatal depression and anxiety among mothers were associated with difficult temperaments, whereas some denied the causal relationships. A variety of infant temperaments were moderately or weakly associated with the dysphoric moods such as negative affectivity, emotionality, activity, fussiness, poor attention, and fearfulness. | ||
| 4.1.2. | Psychological stress | 5 | 1, 3, 8, 9, 27 | Prenatal psychological stress due to severe stressful events predicted lower or higher surgency, regulation, fussiness, dullness and poor attention. | ||
| 4.1.3. | Mindfulness | 1 | 7 | Maternal mindfulness is negatively related to difficult temperament of the child. | ||
| 4.1.4. | Eating disorder | 1 | 15 | Infants of mothers diagnosed with an eating disorder following Anorexia Nervosa, Bulimia Nervosa, Eating Disorder Not Otherwise Specified and Binge Eating Disorder scored higher on ‘fussiness' than the un-exposed group. | ||
| 4.2. | Personality | |||||
| 4.2.1. | Anxiety trait | 2 | 2, 26 | Infants of mothers with higher anxiety traits showed negative emotionality and poor attention. | ||
| 4.2.2. | Alexithymic trait | 1 | 6 | Alexithymic trait in mothers, i.e., difficulty in identifying their feelings, predicted higher infant duration of orienting. | ||
| 4.2.3. | Perfectionistic trait | 1 | 16 | A higher level of adaptive perfectionism was negatively related to difficult temperament of the child. | ||
| 5. | Obstetric factors | 5.1. | Fetal growth | |||
| 5.1.1. | Fetal growth | 1 | 19 | No significant relationship with fetal growth restriction. | ||
| 5.1.2. | Birth weight (overweight, underweight) | 2 | 11, 22 | A very small relationship with overweight at birth. | ||
| 5.2. | Pregnancy complication | |||||
| 5.2.1. | Gestational hypertension | 1 | 12 | Maternal hypertensive disorders were associated with difficult temperament. | ||
| 5.2.2. | Maternal nausea | 1 | 31 | Nausea in middle or late pregnancy was associated with lower sensory thresholds and higher level of activity and emotional intensity among infants. | ||
| 5.3. | Delivery complication | |||||
| 5.3.1. | Preterm delivery | 1 | 34 | Combination of preterm delivery and low birth weight was associated with difficult temperament. | ||
| 5.3.2. | Instrumental delivery | 1 | 33 | No significant relation between vacuum delivery and difficult temperament. | ||
| 5.3.3. | Artificial Reproductive Therapy | 1 | 13 | Mothers who received ART reported lower trait and state anxiety and infants had lower scores on difficult temperament. | ||
1. Number: Number of relevant articles, 2. Article Number: Article number referred to Appendix 2.