Women who think they might be pregnant are urged to delay vaccination until they are certain they are not, and those trying for a baby should not be immunised either.
However, the measure is purely precautionary and it is not uncommon to exclude some groups from taking brand new vaccines.
Pfizer's vaccine sailed through approval from Britain's medical watchdog with a good safety rating and no evidence to suggest pregnant women are at risk.
But scientists behind the jab haven't tested it on pregnant or breastfeeding women – often the case in scientific trials for ethical reasons – so there is no concrete evidence showing it would be safe and effective.
Pregnancy, the new virus and vaccines are 'a constantly evolving area' which needs further research, as there is very limited experience in trials on pregnant women, according to Prof Chappell.
She hopes that vaccine companies may change this situation in the future.
Women who are in the highest risk Covid-19 groups, such as carers and health workers or the clinically extremely vulnerable such as those with underlying health conditions, should try to have 'a sensible discussion' about their concerns about the jab.
They are among the first phase of people to be vaccinated and their obstetrician or midwife is the obvious person to try and seek useful information from.
Prof Chappell suggested that 'we may be in a different place in six months in terms of how we can have those discussions' as new and updated information comes through from the real-life current use of vaccines.
Bigger trials are needed involving pregnant women to help answer questions about safety and risk but how the woman views her risk of exposure and complications is an important factor that needs to be taken into the mix.
Article source: 15th January www.dailymail.co.uk