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COVID -19 and Pregnancy

Possible Transmission of COVID-19 From an Infected Mother to Her Newborn

Controversy exists regarding whether SARS-CoV-2 can be transmitted in utero from an infected mother to her infant before birth.  It is important to understand that this disease has only been recognized for only 3 months, and therefore, there are many unanswered questions regarding this virus.

Just this week, there have been three reports in the Journal of the American Medical Association (JAMA) regarding these issues.

In the first report, a series of 9 pregnant women in China found no mother-to-child transmission of the virus.  A recent research letter reports on a mother who was permitted to the hospital at 34 weeks of pregnancy and found to have COVID-19 infection.  Because of respiratory complications, she was delivered at 38 weeks by cesarean section.  Before birth, testing for virus in her vaginal secretions was negative.

The baby had no symptoms and was immediately quarantined from the mother. A viral testing of the baby showed no evidence of an active infection with the virus at birth and persisted in being negative up to 16 days of age.  At 2 hours of age, the COVID-19 IgG level was 140.3 and the IgM level was 45.8 (normal IgM and IgG <10).   At 16 days, the IgM (11.75) and IgG (69.94) levels were still elevated.

The elevated IgM antibody level suggests that the neonate was infected in utero. IgM antibodies are not transferred to the fetus via the placenta.  The infant potentially could have been exposed for 23 days from the time of the mother’s diagnosis of COVID-19 to delivery.  Although infection at delivery cannot be ruled out, IgM antibodies usually do not appear until 3 to 7 days after infection, and the elevated IgM in the neonate was evident in a blood sample drawn 2 hours after birth.

In the second report from China, six pregnant women with mild clinical manifestations of COVID-19 were delivered by cesarean sections in their third trimester.  The infants were quarantined from the mothers right after delivery.  All infants had antibodies detected in their serum.  Two infants had both IgG and IgM detected.  None of the infants had virus detected in throat swabs and blood samples.  None of the infants presented with any symptoms of disease.  However, virus-specific antibodies were detected in neonatal blood sera samples.   Because IgG is passively transferred across the placenta from mother to fetus beginning at the end of the second trimester and reaches high levels at the time of birth, this is not unexpected.  However, IgM that was detected in 2 infants is not usually transferred from mother to fetus because of its larger macromolecular structure.  Alternatively, IgM could have been produced by the infant if the virus crossed the placenta during pregnancy.

In a third study from China, Thirty-three neonates were born to mothers with COVID-19, 3 neonates were identified with with COVID-19.  All three patients were delivered by cesarean section at term because of maternal COVID-19 pneumonia.  The three infants with positive COVID-19 showed positive nasopharyngeal and anal swabs for all Covid-19 on days two and four of life but were negative by day 6-7.  Samples taken from patients, including amniotic fluid, cord blood, and breast milk, were negative for COVID-19.  The most common symptom was shortness of breath (4 of 33 neonates).  No deaths were reported.  The investigators did not perform IgG or IgM testing on the infants.

In an editorial in the March 26 issue of JAMA responding to these reports, the authors applauded the researchers for exploring the possibility that COVID-19 virus might be passed to the neonate.  However, they critically analyze the available data and had many questions that cannot yet be answered.

The suggestion that in utero transmission occurred rests on the detection of IgM in 3 neonates.  They explained that IgM is a challenging way to diagnose congenital infections.  Although IgM antibodies are too large to cross the placenta and so detection in a newborn reasonably could be assumed to reflect fetal production following in utero infection; however, congenital infections are not diagnosed based on IgM detection because IgM assays are prone to false-positive and false-negative results, along with cross-reactivity and testing challenges.  Generally an in utero infection is confirmed by the presence of the infectious agent in the neonate.

Additionally, the kinetics of decline of the IgM was uncharacteristically rapid compared to the usual rates of decline in other congenitally transmitted infections. The neonate’s IgM value declined from 45.8 at 2 hours of life to 11.7 on day 14 of life, just above the threshold of 10 that constitutes a positive result.  This decline in IgM concentration is very rapid.  In infants with congenital rubella syndrome, rubella-specific IgM can be detected for several months, with about a third having detectable IgM from 6 months to 2 years of age.  Likewise, IgM following congenital Zika infections can persist for a year or longer.  While the kinetics of IgM production and decay in COVID-19 infections are not yet known, the rapid decline reported in the report raises the possibility that the laboratory findings in these 3 infants are not evidence of true congenital infection but rather could represent artifact.

In conclusion, the editorial stated that "given the modeling showing that a significant percentage of the world’s population, many of them pregnant women, will be infected over the next weeks or months—this issue is one that deserves careful consideration. However, at this time, these data are not conclusive refuted or prove in utero transmission."

It is also noteworthy, that none of the reports suggested any significant disease in the infants that could be attributed to the COVID-19 virus.  However, it is important to realize that these are very small numbers of cases and more importantly they all involve patients who were infected in the third trimester of pregnancy.  As this pandemic evolves, our understanding of any effects that the virus may have on pregnancy will also continue to evolve.

What should pregnant women do to avoid the coronavirus?

The virus spreads mainly from person-to-person contact, either through aerosol or transfer from contaminated objects. Pregnant women can take the same steps as the rest of us protect themselves.  These steps include:

  • Washing hands often with soap and water for at least 20 seconds
  • Cleaning hands with a hand sanitizer that contains at least 60% alcohol if you can’t wash them (rub until your hands feel dry)
  • Avoid touching your eyes, nose, and mouth (unless you have just washed your hands)
  • Practicing "shelter in place" (staying home as much as possible)
  • Practicing "social distancing" (staying at least 6 feet away from other people) if you need to go out 
  • Avoiding people who are sick

What should pregnant women do during pregnancy?

Currently available data on COVID-19 does not indicate that pregnant women are at increased risk. However, pregnant women are known to be at greater risk of severe morbidity and mortality from other respiratory infections such as influenza and SARS-CoV. As such, pregnant women should be considered an at-risk population for COVID-19. 

It’s too early for researchers to know how COVID-19 might affect a fetus. Some pregnant women with COVID-19 have had preterm births, but it is not clear whether the preterm births were because of COVID-19.  In the limited number of women who have delivered their babies, the prematurity rate is no different than in the normal population.

Although the currently available studies are very reassuring and have shown no adverse affects on the pregnancies or infants, more definitive evidence is needed before we can counsel pregnant women that their fetuses are at no risk of congenital infection with COVID-19.

Should pregnant women wear a face mask?

Pregnant women who are feeling well do not need to wear a mask.  If you think you may have been exposed to the coronavirus and have a fever or cough, call your ob-gyn or other health care professional for advice.  If you have COVID-19 or have symptoms, you should wear a mask while you are around other people. 

What should new mothers do?

So far, the virus has not been found in breast milk. But there is not enough information yet on whether women who are sick can pass the virus through breast milk. 

Breast milk gives babies protection against many illnesses. It also is the best source of nutrition for most babies. Talk with your ob-gyn or and your pediatrician about whether to start or continue breastfeeding. 

Currently, the primary concern is not whether the virus can be transmitted through breastmilk, but rather whether an infected mother can transmit the virus through respiratory droplets during the period of breastfeeding. A mother with confirmed COVID-19 or who has symptoms should take all possible precautions to avoid spreading the virus to her infant, including washing her hands before touching the infant and wearing a face mask, if possible, while breastfeeding.

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