A study by Yale researchers has shown that the genetics of the foetus and placenta drive developmental abnormalities, including those that lead to pregnancy loss and autism.
In the US, a birth defect is diagnosed in about 3% of children born every year, according to the Centers for Disease Control and Prevention. Birth defects also occur in most cases of pregnancy loss, and also result in many deaths in the first year of life. The causes are thought to be a complex interplay of environmental and biological factors.
“Mothers often feel that they are responsible for these defects,” explained senior author Dr Harvey Kliman, Research Scientist at the Department of Obstetrics, Gynecology & Reproductive Services, Yale School of Medicine. “But it’s not their fault. This new research points to the genetics of these children as being the most important cause.”
Dr Kliman and his team examined placental data for nearly 50 sets of identical and non-identical twins. They discovered identical twins had similar numbers of abnormal cell growths called trophoblast inclusions (TIs), which are markers for a number of developmental abnormalities, while non-identical twins showed a markedly different TI count.
While identical twins share the same DNA, non-identical twins only share half of their DNA. Identical twins were found to often have the same number of TIs or were within one of having the same TI count. Non-identical twins had TI counts that differed by four or five on average.
“This work suggests that developmental abnormalities are much more likely to be due to the genetics of the child, and not the mother’s fault,” Dr Kliman explained.
The findings were reported in the journal Placenta.
First author Julia Katz, a former Yale undergraduate and now medical student at Hofstra University, provided the inspiration for the study.
Katz and her brother, Jesse, who was born underweight and with several congenital abnormalities, are non-identical twins. “I had a lot of guilt, growing up, about why my twin had certain conditions that I didn’t,” Katz explained. “I think mothers also tend to blame themselves.”
After a lecture, Katz approached Dr Kliman and asked him what causes babies to be born undersized, a conversation which led to a discussion about developmental abnormalities and Katz’s desire to find out more about her and her twin’s genetics — including looking at her own placental slides from birth.
It also led Dr Kliman, Katz, and co-author Parker Holzer, a graduate student in the Yale Department of Statistics and Data Science, to conduct the new study.
“Julia’s need to resolve this burden is what propelled our study,” Dr Kliman said. “Hopefully, this finding will help many other people, as well.”
“This experience has shown me that if you have a question, ask it,” Katz added. “And if you don’t get an answer, try to answer it yourself.”
Source: News-Medical.Net
Journal information: Katz, J., et al. (2021) Genetics, not the uterine environment, drive the formation of trophoblast inclusions: Insights from a twin study. Placenta. doi.org/10.1016/j.placenta.2021.04.010.
