Intergenerational transmission of the effects of maternal childhood adversities via poor infant outcomes

BACKGROUND: The effects of maternal exposure to adverse childhood experiences (ACEs) may be transmitted to the subsequent generation through various biopsychosocial mechanisms. Previous studies have found an association between maternal ACEs and poor infant outcomes (i.e., preterm birth and low birthweight). Further, evidence suggest that one intermediary mechanism is through a behavioural pathway, specifically, through the use of substances (i.e., tobacco, alcohol, illicit drugs) during pregnancy. This doctoral thesis aimed to explore the associations between maternal ACEs, prenatal substance use, and poor infant outcomes. METHODS: To address this overarching research question, a systematic review and meta-analysis was conducted. Additionally, various statistical analyses (i.e., multilevel logistic regression with marginal effects, mediation analyses, and latent class analyses) were performed using the Evidence for Better Lives Study (EBLS) dataset (n = 1189). Moreover, the research focus was expanded by exploring the interrelationships of maternal ACEs, a wide array of biopsychosocial and environmental risks during pregnancy, and the adverse infant outcomes of interest by conducting network analysis using the Avon Longitudinal Study of Parents and Children (ALSPAC) dataset (n = 8379). RESULTS: Results from the review and the multilevel models indicate a positive association between threshold ≥ 4 threshold ACEs and prenatal substance use but not with poor infant outcomes. Additionally, results from the mediation analyses found no evidence to suggest that prenatal substance use played a mediating role between the former and the latter. The marginal effects analyses identified childhood physical abuse and parental incarceration, respectively, as individual risks with the highest predictive probabilities for prenatal smoking. Domestic violence exposure and neglect were the individual risk factors for prenatal alcohol use, having a household member with mental illness was the individual risk factor with the highest predictive probability for prenatal illicit drug use and childhood sexual abuse in relation to adverse infant outcomes. The LCA identified three high-risk classes and one low-risk class, namely: (1) highly maltreated (7%), (2) emotionally and physically abused with domestic violence exposure (13%), (3), emotionally abused (40%), and (4) low household dysfunction and abuse (40%). Pairwise comparisons between classes indicate that class 1 and 3 had higher probabilities of prenatal illicit drug use compared to class 4. Additionally, class 2 had higher probability of low birthweight compared to the three remaining classes. Finally, results from the network analyses indicate that childhood and prenatal risk factors were highly interrelated. Childhood physical abuse, but not ≥ 4 threshold ACEs, was directly associated with low birthweight. In addition, childhood sexual abuse played a central role in bridging ACEs to other risks and to the outcomes of interest. Overall, prenatal smoking was determined as the most influential prenatal risk factor. This thesis has implications for research, policy, and practice. The results illuminated the dynamic and multifaceted nature of ACEs and their deleterious impact on maternal behavioural outcomes during pregnancy. Despite of this, it was also evident that greater specificity is warranted, by paying further attention to various parameters of risk exposure and risk and protective factors at different levels of the individual’s social ecology in order to gather a more accurate representation of its impact on adult and infant health. Also, consensus is needed in research in how ACEs are constructed, measured, coded, and analysed before we can start teasing out similarities and differences across cultures. Smoking cessation during pregnancy should be a key target to improve lifelong health and promote healthy child development. Policymakers should consider investing in cessation services that are integrated in antenatal health services where trauma-informed principles are embedded in practice; where social, cultural, and organisational stigma are addressed; and the focus lie in enhancing support rather than directing blame