During pregnancy, the immune system adapts in order to prevent “rejection” of the growing foetus and placenta. Consequently, the ability to fight off a viral infection is reduced. Respiratory viruses result in greater risk of complications like pneumonia and ARDS. This is due to hormonal changes and the compressive effect of the uterus on the diaphragm towards the end of pregnancy, which affect lung function.
The H1N1 2008 pandemic was a sobering experience globally for healthcare professionals. During that pandemic, pregnant women were four times more likely to be hospitalised compared to the non-pregnant population. In the UK, 241 women were admitted to hospital with 20 per cent admitted to the ICU; higher rates than normal of preterm labour were seen. The maternal mortality rate was 1.6 per 100,000 pregnant women Babies were affected, with increases in stillbirth and early neonatal death observed.
The experience with H1N1 in pregnancy led to many of us fearing the worst when SARS-CoV 2 was declared a pandemic by the WHO. Data thus far has been reassuring.
A case series of 43 pregnant women in New York found that infection severity in pregnancy was similar to non-pregnant adults, with 86 per cent of women who got infected, getting mild disease, 9 per cent getting severe disease and 5 per cent getting critical disease. A second study involved 215 women who were screened for SARS Cov 19 on presentation. 15 per cent tested positive; of those with positive tests, most were asymptomatic with four women, representing less than 2 per cent, having symptoms.
Preliminary UK data from the Intensive Care National Audit indicated that the rate of admission to the ICU for pregnant women was similar to the rate of non-Covid 19 pneumonia for the previous 2 years.
With regard to the outcomes of babies, no studies have suggested an increase in rates of miscarriage or anomalies. The data on increased rates of preterm labour is unclear, as any acute systemic illness raises the risk of preterm labour. In terms of whether the virus can be transmitted to babies whilst mothers are still pregnant (vertical transmission), Chinese data is reassuring and suggests that this has not been observed.
UK-specific pregnancy data is now available from the UK Obstetrical Surveillance System (UKOSS), a national system to study rare disorders in pregnancy.
427 women who tested positive for SARS-CoV 2 infection and were admitted to UK hospitals had their data analysed; a rate of infection in pregnancy of 4.9 per 1000 pregnant women was observed.
80 per cent of women were symptomatic in their 3rd trimester or around the time of delivery. The most common symptoms were( in decreasing order) fever, cough, breathlessness, tiredness, limb pain, headache, sore throat, vomiting, diarrhoea or runny nose.
Risk factors for admission to hospital were being BAME, older age, obesity or having pre-existing medical disease like diabetes or hypertension.
10 per cent of women were admitted to a level 3 ICU; tragically, five women died as a result of SARS-Cov 2 infection. The maternal mortality rate in the UK thus far, is 5.6 deaths per 100,000 pregnant women, which exceeds the death rate of H1N1 influenza.
Rates of the birth of a live baby, stillbirth, pregnancy loss and neonatal death (babies dying after delivery), were comparable to women unaffected by SARS-Cov-2. 25 per cent of babies were admitted to the NICU; 4 per cent of babies tested positive for SARS Cov 2. This could represent vertical transmission, but equally, infection during/following birth. Rates of preterm labour were only increased for the 28-31 weeks gestational-age period. Around 60 per cent of women needed to be delivered by C-section, mostly due to concerns about the baby’s heart rate, in contrast to an early report of 108 patients, where a rate of 90 per cent was observed.
The cumulative data suggests that pregnant women are no more likely to contract infection than non-pregnant women and that almost 90 per cent will experience mild disease if infected with SARS CoV 2. Should they get infected, they are more likely to be symptomatic in the 3rd trimester. If severe disease occurs, pregnancy itself does not appear to alter the outcome, unlike the case in other specific viral infections. Babies are not at higher risk of stillbirth or neonatal death, but an expected increase in preterm labour, particularly at 28-31 weeks of gestation, occurs. Should women present at the end of pregnancy, they will successfully deliver healthy babies who will survive. They are at higher risk of delivering by C-section.
Breastfeeding is an option for women who contract SARS CoV 2, provided adequate precautions are taken to limit the risk of infection to the baby.
Despite this reassuring data, pregnant women are by definition a vulnerable group and hence should observe social distancing, particularly above 28 weeks gestation, self-isolate per Government guidelines, wash their hands frequently, and avoid touching their eyes, nose and mouth. If they experience fever, cough or breathing problems, they must seek immediate care by phoning the NHS on 111, the maternity unit or 999.
The Royal College of Obstetricians and Gynaecologists has published advice for women and their families on the subject.