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There is increasing evidence that prenatal stressful life events (SLEs) may be a potential risk factor for attention-deficit hyperactivity disorder (ADHD), but the sex-specific and time-dependent effects of prenatal stress on ADHD are less clear. In this prospective longitudinal study, data on prenatal SLEs during different stages of gestation and indicators of buffers against stress, including maternal social support and avoidance coping, were obtained from 1765 pregnant women at 32 weeks of gestation. The behavioral symptoms of ADHD in children aged 48-54 months were evaluated by reports from the parents. There were 226 children (12.8%) above the clinically significant cutoff for ADHD. After adjusting for potential confounders, boys whose mother experienced severe SLEs in the second trimester had a significantly increased risk (OR = 2.41, 95% CI: 1.03-5.66) of developing ADHD symptoms compared with boys whose mothers did not experience severe SLEs at this time. However, no significantly increased risk of ADHD symptoms was observed in girls born to mothers experienced prenatal severe SLEs. Additionally, significant interaction effects of prenatal SLEs, social support and coping style on ADHD symptoms were found in males. Boys whose mothers experienced severe SLEs during the second trimester accompanied by a higher score for avoidance coping (OR = 3.31, 95% CI: 1.13-9.70) or a lower score for social support (OR = 4.39, 95% CI: 1.05-18.31) were likely to be at a higher risk for ADHD symptoms. The epidemiological evidence in this prospective follow-up study suggests that the effect of prenatal SLEs on ADHD symptoms in offspring may depend on the timing of prenatal stress and may vary according to the sex of the offspring.

This prospective study suggested that there was an inverted-U-shaped relation between neonatal vitamin D status and neurocognitive development in toddlers. Additional studies on the optimal 25(OH)D concentrations in early life are needed.

AIM The aim of this study was to assess the cognitive and behavioural development of children with healthy birth outcomes whose mothers were exposed to prenatal stress but did not experience pregnancy complications. METHOD In this prospective study, self-reported data, including the Prenatal Life EventsChecklist about stressful life events (SLEs) during different stages of pregnancy, were collected at 32 to 34 weeks' gestation. Thirty-eight healthy females (mean age 27y 8mo, SD 2y 4mo) who were exposed to severe SLEs in the first trimester were defined as the exposed infant group, and 114 matched comparison participants were defined as the unexposed infant group (1:3). Maternal postnatal depressive symptoms were assessed with the Edinburgh Postnatal Depression Scale. The Bayley Scales of Infant Development and the Toddler Temperament Scale were used to evaluate the cognitive development and temperament characteristics of the infants with healthy birth outcomes when they were 16 to 18 months old.RESULTS A randomized block multivariate analysis of covariance showed that the mental development index scores of the infants of mothers with prenatal exposure to SLEs in the first trimester averaged seven points (95% confidence interval 3.23-10.73 points) lower than those of the unexposed infants. Moreover, the infants in the exposed group achieved higher scores for regularity (adjusted mean [SD] INTERPRETATION This study provides evidence that lower cognitive ability and less optimal worse behavioural response in infants might independently result from prenatal maternal stress.Studies carried out using animal-based models present evidence that exposure to prenatal stress may increase vulnerability to atypical cognitive and neurobehavioral development, altering the development of several brain areas (including the prefrontal cortex, hippocampus, and amygdala) and the programming of the hypothalamicpituitary-adrenal axis.1,2 A certain amount of life stress is unavoidable for humans. A substantial body of evidence, however, has linked maternal exposure to stressful life events (SLEs) during pregnancy with cognitive and behavioural development in the offspring. The early stages of pregnancy in humans, from 8 to 24 weeks' gestational age, are particularly important for development. During this period, major neurodevelopmental events occur, including the proliferation, differentiation, and migration of neurons. Several brain areas, such as the hippocampus and amygdala, are already differentiated during this period.3,4 Our previous study, and others 5,6 have shown that maternal exposure to SLEs in the first trimester is associated with adverse birth outcomes and lower general intellectual ability. It is rational to postulate that stress during the first trimester might interfere with neurodevelopmental processes, resulting in atypical cognitive and behavioural development.Ecological investigations have found that prenatal exposure to a natural disaster is associated with lower cognitive and language abilities.6 Population-ba...