Several maternal chronic conditions increase the risk of giving birth to a child with cerebral palsy, based on data from more than 1.3 million Norwegian children.
Dr. Alastair MacLennan
Mothers with autoimmune disorders, such as diabetes and lupus, had the greatest risks, reported lead author Marianne S. Strøm, MD, of the University of Bergen (Norway) and colleagues.
“The etiologies of cerebral palsy are complex, and only a few prenatal risk factors have been identified,” the investigators wrote in Pediatrics. “Among these possible risk factors are maternal chronic conditions, although studies are typically underpowered and limited to one or two conditions.”
According to Dr. Strøm and colleagues, several components of maternal chronic conditions have been linked with cerebral palsy, including placental abnormalities, altered thrombotic state, and inflammation. Furthermore, mothers with chronic conditions are more likely to give birth prematurely and have children with congenital malformations, both of which have also been associated with cerebral palsy.
To date, however, “there has been no systematic description of maternal chronic conditions and risk of cerebral palsy in offspring,” the investigators noted.
The present, prospective cohort study aimed to meet this need with a population of 1,360,149 children born in Norway from 1990 to 2012, among whom 3,575 had cerebral palsy. Case data were extracted from the Norwegian Patient Registry and the National Insurance Scheme. Information about maternal chronic conditions was extracted from the Medical Birth Registry of Norway and the Norwegian Patient Registry, with the latter also providing information about paternal chronic conditions.
Using log binomial regression models, the investigators determined relative risks of having children with cerebral palsy among parents with chronic conditions versus parents from the general population. This revealed that chronic conditions in fathers had no correlation with cerebral palsy. In contrast, mothers with chronic conditions had a 30% increased risk (relative risk, 1.3; 95% confidence interval, 1.2-1.5), which could be further stratified by number of chronic conditions; mothers with one chronic condition, for instance, had a 20% increased risk (RR, 1.2; 95% CI, 1.1-1.4), while those with two chronic conditions had a 60% increased risk (RR, 1.6; 95% CI, 1.1-2.2), and those with more than two chronic conditions had triple the risk (RR, 3.1; 95% CI, 1.4-6.8)
“The lack of associations between the father’s chronic illness and cerebral palsy risk supports the interpretation that cerebral palsy risk in offspring is the direct result of the mother’s condition and not genetic predisposition or unmeasured situational factors,” the investigators wrote.
Maternal autoimmune conditions were particularly relevant, as they were associated with a 40% increased risk of cerebral palsy (RR, 1.4; 95% CI, 1.1-1.7), a rate that climbed dramatically, to 270%, among mothers with more than one autoimmune condition (RR, 2.7; 95% CI, 1.1-6.6).
“The role of autoimmune diseases in cerebral palsy risk (and maternal inflammation specifically) deserves closer attention,” the investigators wrote. “Using studies with larger sample sizes and a more clinical focus, including measures of placental structure and perinatal blood assays, researchers may be able to explore these possible connections between maternal autoimmune diseases and fetal neurodevelopment.”
Specifically, cerebral palsy in offspring was most strongly associated with maternal Crohn’s disease (RR, 2.1; 95% CI, 1.0-4.1), type 1 diabetes (RR, 2.2; 95% CI, 1.4-3.4), lupus erythematosus (RR, 2.7; 95% CI, 0.9-8.3), and type 2 diabetes (RR, 3.2; 95% CI, 1.8-5.4). Associations were also found for migraine (RR, 1.6; 95% CI, 1.2-2.2), multiple sclerosis (RR, 1.8; 95% CI, 0.8-4.4), and rheumatoid arthritis (RR, 2.0; 95% CI, 1.3-2.9). Several “weaker and less convincing associations” were detected for ulcerative colitis, thyroid disorder, epilepsy, asthma, anemia, and hypertension. Adjusting for parental education level, age, smoking status, and single-mother status did not significantly alter findings. Poisson and logistic regression models generated similar results.
In an accompanying editorial, Sandra Julsen Hollung, PhD, of the Cerebral Palsy Registry of Norway, Vestfold Hospital Trust, Tønsberg, and colleagues, advised that clinicians maintain perspective when discussing these findings with the general public.
“As the authors state, the absolute risk of cerebral palsy associated with at least one chronic maternal condition is low,” wrote Dr. Hollung and colleagues. “Among 1,000 pregnant women with any chronic and/or autoimmune disorder, more than 990 will deliver an infant who will not be diagnosed with cerebral palsy.”
They went on to emphasize that the study findings should not be viewed as firm evidence of causal relationships.
“Thus, the study cannot give clues to any specific preventive treatment,” wrote Dr. Hollung and colleagues. “However, if these disorders are part of a causal pathway, optimal treatment might reduce the risk of cerebral palsy.”
Although Dr. Hollung and colleagues advised that such efforts “would hardly affect the birth prevalence of cerebral palsy,” they also cited the Royal College of Obstetricians and Gynaecologists in the United Kingdom, noting that “each baby counts.”
Emeritus Professor Alastair MacLennan, AO, MB ChB, FRCOG, FRANZCOG, head of the Australian Collaborative Cerebral Palsy Research Group at the University of Adelaide (Australia) suggested that the findings may guide future research.
“An increasing proportion of cerebral palsy cases are being diagnosed by genome sequencing and other genetic techniques to have causative genetic variations,” Dr. MacLennan said. “The possibility of epigenetic interactions are also likely and are still to be investigated. Maternal disorders such as diabetes, lupus, or Crohn’s disease are possible epigenetic factors and this study helps to target these in future genetic and environmental studies of cerebral palsy causation. The days of attributing cerebral palsy to ‘birth asphyxia’ are over.”
The study was supported by the National Institutes of Health and the Western Norwegian Regional Health Authorities. The investigators reported no conflicts of interest.