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New Study: Low Maternal Progesterone Linked to Autism
A study published online in the journal Medical Hypotheses suggests a possible link between low maternal progesterone and autism. In the paper, titled “Low maternal progesterone may contribute to both obstetrical complications and autism,” a team of Stony Brook University researchers, led by Professor of Integrative Neuroscience Patricia Whitaker-Azmitia, Ph.D., interviewed mothers with and without an autistic child (matched on various characteristics). They found a link between autism and factors that indicate low levels of maternal progesterone. The study revealed that continued use of birth control pills during pregnancy was the single largest influence on having an autistic child, increasing the odds of having an autistic child by a factor of nine.
Dr. Whitaker-Azmitia, a neuropharmacologist who studies brain development and autism, and colleagues found that excess weight during pregnancy was the second largest influence on having an autistic child, which increased the chances of having an autistic child by a factor of 3.6. The study also showed other factors that indicate low levels of maternal progesterone are associated with autism. These include vaginal bleeding during pregnancy, the use of fertility drugs, and difficulties conceiving.
Past research has shown an association between autism and adverse health effects or complications during pregnancy. Many pregnancy complications can be linked to low levels of maternal progesterone. Dr. Whitaker-Azmitia and colleagues take this association a step further to draw a direct line between low levels of maternal progesterone and autism.
“Although the association of low progesterone and obstetrical complications has been known for 30 years, the idea that progesterone is not only a factor responsible for a healthy pregnancy but also as a major brain development factor is new,” said Dr. Whitaker-Azmitia. “This premise is the basis of our hypothesis, which adds to the body of research investigating environmental causes of autism and in this case the in utero environment.
“If our hypothesis proves to be true, then careful monitoring of progesterone levels while a woman is pregnant may help to prevent autism in some cases,” she explained.
The authors also suggest that identifying changes in the in utero environment leading to increased risk of autism may potentially be more immediately translated into autism prevention and treatment strategies than targeting genetic links to autism.
Through the Stony Brook University Center for Survey Research, the team used a case control method to match a woman with an autistic child to a woman of the same age with a child of the same age, living in the same geographic area. They obtained a list of households with children diagnosed with autism spectrum disorders from Great Lakes List Management, a direct marketing service provider. The households represented a geographically diverse sample across the United States.
The researchers conducted telephone interviews with 86 women with an autistic child and 88 without an autistic child. Mothers were asked a set of detailed questions about events surrounding the pregnancy and birth of their child.
The authors note clear signals from other research that helped form their hypothesis: Progesterone protects the fetus’s brain from the damaging effects of maternal inflammation and infection, and it can also directly prevent brain cell damage that arises from fetal brain trauma. Progesterone promotes the development of neural circuitry in parts of the brain linked to social behavior, and the development of the serotonin neurotransmitter system. There is also suggestive evidence that the male fetus is more affected than a female fetus by maternal levels of progesterone, which may help to explain higher rates of autism among boys than girls.
Dr. Whitaker-Azmitia points out that more research is needed to fully understand the effects of maternal progesterone levels on the incidence of autism. From the study, they conclude that current lifestyles and health behaviors, including obesity, intense exercise, older mothers, and stress are associated with lower levels of progesterone. The increase in many of these risk factors over time may help to explain the rising incidence of autism.