Doctors in China are reporting an alarming and unexplained spike in fetuses in reverse sitting positions, a rare congenital disorder in which organs in the chest and abdomen are arranged as mirror images of their normal positions.
In the first seven months of 2023, the proportion of fetuses confirmed to have the disease quadrupled compared to historical rates. A short report published Thursday in the New England Journal of Medicine.
For the report, doctors from two large maternity centers in Shanghai and Changsha combined each center’s clinical records from January 2014 to July 2023. Doctors found that from 2014 to 2022, the annual total number of cases of reverse sitting was typically around five. That’s 6 of every 10,000 pregnant women who undergo an ultrasound. But in 2023, this rate has jumped to nearly 24 ultrasounds per 10,000.
Looking at cases by month in 2023, researchers noted that a spike in inversions began in April, continued through June, and returned to background infection rates in July. Between January and July 2023, there were a total of 56 cases of reverse sitting among 23,746 pregnant women who underwent ultrasound examinations.
Ultrasound tests to diagnose the condition were usually performed between 20 and 24 weeks of pregnancy. The authors noted that there were no changes in diagnostic criteria that could explain the “significant increase.”
“No conclusion has been reached.”
Although there is no supporting evidence, doctors speculate that it may be related to the surge in coronavirus infections that began in late 2022, when China abruptly lifted its zero-COVID-19 policy. The subsequent wave of coronavirus infections ultimately infected about 82 percent of China’s population of more than 1.4 billion people, the authors write. The number of new coronavirus infections peaked at the end of December, and the wave continued until early February.
Approximately four months after the peak of the number of new coronavirus infections, a reversal of the increase began. The authors speculate that the virus may have caused the condition by directly infecting the fetus in the womb, or indirectly through maternal inflammatory responses.
But this is all highly speculative. First, the report will ask whether pregnant women whose fetuses were diagnosed with rare diseases were infected with COVID-19 during pregnancy, and what their SARS-CoV-2 infection rates are. It does not include data on how this compares to a pregnancy without a reverse sitting position. . It also does not include data on genetic and environmental factors known to be associated with inversion. And, of note, although cases of reverse locus have increased four-fold, they remain very rare overall and have been linked to other SARS-CoV-2 cases, including after the pandemic first began in China in late 2019. No such surge was reported in the second wave of infections.
As such, the authors acknowledge that “no conclusions can be drawn” from the current report about the cause of the abnormal spikes. However, they call for further research to understand what is behind the increase and the possible role of SARS-CoV-2. The good news is that most patients with inverse sitting have a normal lifespan.
