Covid increases risk of pregnancy complications, harmful to placenta growth, universities in Hong Kong discover
- Joint study by University of Science and Technology, Chinese University shows SARS-CoV-2 virus can significantly disrupt development of placenta in pregnant women
- Researchers find viral infection triggers significant increase in woman’s immune response, reducing genes known to stop blood clots and support fetus growth
Pregnant women who contract Covid-19 face an increased risk of complications such as preterm birth and, in the worst case, a stillborn child, a joint study by researchers at Hong Kong universities has found.
The SARS-CoV-2 virus, which causes Covid-19, significantly disrupted the development of the placenta in pregnant women, especially those in their third trimester, academics from the University of Science and Technology (HKUST) and Chinese University (CUHK) said on Thursday.
“The placenta is a very vascular organ and the formation of the placenta requires new blood vessels to support the growth of the fetus,” said Dr Liona Poon Chiu-yee, head of the obstetrics and gynaecology department at CUHK’s faculty of medicine.
“Abnormal blood vessel formation within the placenta will restrict the growth of the fetus as the placenta cannot provide sufficient nutrition and oxygen.”
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Irregular development of the placenta might lead to pre-eclampsia, a form of hypertension in pregnant women, and gestational diabetes.
Pre-eclampsia can cause serious complications such as stroke and premature births and affects around three to five pregnant women in every 100 in Hong Kong.
Insufficient nutrients and oxygen delivered by the placenta might result in the fetus being a low-weight, preterm birth and in the worst case, cause stillbirth.
The team from the two universities collected samples from the placenta and uterus wall of 14 pregnant women in Hong Kong over two years, including seven infected with Covid-19 in their third trimester.
Of the seven, five showed Covid-19 symptoms. The infected women, aged between 27 to 42, were on average 35.9 weeks into their pregnancy when diagnosed with the coronavirus.
While Covid-19 does not transmit directly from the mother to the fetus, the team found that the viral infection triggered a significant increase in the woman’s immune response, which affected her gene activity.
The team also found that infected mothers-to-be had more than 70 per cent fewer pregnancy-specific glycoprotein (PSG) genes in their placenta compared with uninfected women.
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“Covid-19 patients have a significantly lower level of PSG genes in their placenta,” said Danny Leung Chi-yeu, director of the Centre for Epigenomics Research at HKUST.
“PSG genes are known to stop blood clots and control the immune response of the mother, which can impact fetus health.”
The research supports the finding of a previous study of more than 13,000 pregnant women by George Washington University in the United States, which found that those infected with SARS-CoV-2 faced a sevenfold increase in the risk of death, while their newborns faced a higher risk of preterm birth and low birthweight.
Poon also warned mothers-to-be against delaying their Covid-19 jabs and stressed the importance of virus prevention.
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“The reluctance of getting vaccinated before pregnancy is a major issue. A lot of women are still worried about the effects of vaccination on their ability to get pregnant but that has not been proven,” she said.
Poon added that pregnant women who got vaccinated also passed on antibodies to their newborn through the umbilical cord, protecting them from Covid-19.
“If you don’t get vaccinated during pregnancy, your newborn will not be protected from Covid during the first six months because they are not going to get vaccinated immediately after birth.”
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Poon also urged expectant mothers to actively test themselves to get timely treatment even as society exited the pandemic.
“Even in these cases where they didn’t have a severe form of Covid-19, we already saw such severe impact in the maternal-fetal interface, let alone a severe Covid-19 case,” she said.
“Upon detecting the infection, we need to provide additional pregnancy care, including more frequent monitoring through ultrasound and cardiotocography to check the infant’s heart rate.”
