In a recent JAMA article, a team of Swedish researchers looked to identify any complications in the newborn due to infection with SARS-CoV-2 during pregnancy. To do this, they looked at 2323 infants delivered by mothers who tested positive for the virus. Here is what they found:

  • Infection increased admissions for neonatal care (11.7% vs. 8.4% in normal pregnancies)
  • Infection was associated with neonatal respiratory disorder (2.8% vs. 2.0% in normal pregnancies)
  • Infection was associated with respiratory distress syndrome (1.2% vs. 0.5% in normal pregnancies)
  • Infection was associated with high bilirubin (3.6% vs. 2.5% in normal pregnancies)
  • Infection was associated with mortality (0.3% vs. 0.12% in normal pregnancies).
  • Breastfeeding rates and length of stay in the neonatal care did not change compared to normal pregnancies.
  • Only 0.9% infants of infected mothers ended up testing positive for SARS-CoV-2.
  • An active infection during pregnancy can present itself in multiple ways at delivery. One concern is whether the infection itself has compromised the pregnancy. In the case of Covid19 we see an increased rate of respiratory insufficiency in the newborn infant as well as increased mortality. Keep the numbers in mind--in the majority of cases, a pregnant woman infected with the SARS-CoV-2 virus delivers a healthy baby.

    Mortality: Of the 0.3% of infants that did not make it, we find two observations. The first is that more than half were severely pre-term births ranging between 22-28 weeks gestational age. Normal term pregnancies are between 37 and 40+ weeks at delivery. The second observation is that those born at term had respiratory insufficiency and resulting ischemic encephalopathy (or when there is reduced oxygen delivery to the brain).

    Infant Infection Rate: Another concern is whether the infant itself becomes infected during pregnancy or at delivery which would require supportive therapy after delivery and rethinking about preventative steps. Before we talk about infant infection rates, lets understand the model used today for another common infection.

    Group B Strep is a bacteria carried by 1 in 4 pregnant women. Infection rates are between 0.1-0.4% compared to 0.9% for SARS-CoV-2. That number increases to 1-4% in pre-term births. Keep that in mind, because we see the same with SARS-CoV-2.

    Given that the infection rate, and the fact that about 4-6% of infected infants die from the disease, some measures were put in place that anyone who has ever been pregnant knows about. That is the mother is tested for GBS at 36/37 weeks. If the mother tested positive, then she is given IV antibiotics against the bacteria during labor to prevent transmission during birth. This reduces the infection rate of a newborn to a mother who tested positive from 0.5% to 0.025%.

    Another smaller study by Boston Researchers at Beth Israel Deaconess Medical Center found a higher infection rate of newborns with SARS-CoV-2 (2.2% vs. 0.9%) but found the same finding that a big contributing factor to neonatal distress was pre-term birth. They also found that newborns born to mothers with social vulnerability were 5 times more likely to test positive for Covid19. Given how small the sample size in this study was and that fact that they were able to find an association with pre-term birth rates and social vulnerability of the mother points to a likely association between social vulnerability and pre-term births.

    CDC Guidelines: The CDC after reviewing the existing literature also cannot link specific outcomes with the virus but they do note the prevalence of similar outcomes in pre-term births. They do offer the following guidelines:

  • Infected mothers and their newborns should be isolated from others using recommended infection prevention and control practices
  • There is a small risk of transmission to a healthy newborn if the mother is still infected in which case the mother and her doctors need to decide to take precautionary measures such as masks and hand washing.
  • An infected mother can still breastfeed since the virus is transmitted from respiratory droplets.
  • Studies on giving the vaccine to expectant mothers or breastfeeding mothers are limited though data continues to be aggregated. Thus far, there are no safety concerns for expectant mothers receiving the Covid19 vaccine. Some reports have shown that breastfeeding mothers who received the mRNA vaccine (Pfizer or Moderna vaccines) actually had antibodies in their milk which should theoretically protect their babies. This isn't surprising but it needed to be confirmed as all things do.

    The question that a lot of people are wondering is whether a baby born to someone immune against the Covid19 virus would also be immune? The answer is only slightly nuanced because the timing of infection or vaccination matters and the fact that vaccinating newborns is not approved yet so we don't know what level of antibodies is enough to protect them.

    Here is what we do know. In a small study of 83 pregnant women who tested positive for SARS-CoV-2 IgG (meaning they had infection in the past and now it cleared) gave birth to 72 newborns who also had the same antibodies. So 87% of newborns to immune mothers also had antibodies against Covid19.

    Are those antibody levels enough to confer immunity?--We don't know that yet.

    Why aren't 100% of newborns to previously infected mothers also immune?--We don't know but suspect it has to do with the timing of the infection or vaccination. If the expectant mother was infected (and recovered) or vaccinated early in the 2nd trimester, then likelihood of passing the antibodies through the placenta to the fetus is high. The later in the pregnancy the less likely to pass on a sufficient level of antibodies. Thankfully, it is very rare for a virus to cross the placenta compared to antibodies which pass freely which why the J&J vaccine which uses a variant of the live virus may also be an additional vaccine option for expecting mothers .

    While data continues to be collected, here is what likely will be recommended in the future. Expectant mothers who are not infected get vaccinated beginning in the second trimester. Expectant mothers who are infected should talk with their doctors to make sure to take every measure to decrease the likelihood of pre-term births even if that only means increased monitoring. Lastly, if a expectant mother is infected closer to birth, then that means the newborn will not be immune and can have a risk of contracting the virus during delivery or after. That's when infection control measures are important to prevent transmission. If there is transmission of the virus, then one scientific question we are waiting to answer is whether we can safely give newborns an antibody cocktail to reduce the viral load.

    This is new territory for both expectant mothers and their doctors, and that is why there are no restrictive guidelines yet, just scientific research and a lot of common sense until then.