Pregnant women should be asked about previous chickenpox an shingles infections when they book for antenatal care, according to updated guidelines.

Royal College of Obstetricians and Gynaecologists (RCOG) is now suggesting anyone who has not had chickenbox should be told to avoid contact with chickenpox and shingles sufferers and they should let healthcare workers know if they might have been exposed

Many women have antibodies to protect against the virus, which is a common childhood disease, but estimates suggest that chickenpox complicates three in every 1,000 pregnancies.

The guidelines say pregnant women who develop the chickenpox rash should immediately contact their doctor and be referred to a foetal medicine specialist. They also say a neonatologist, who would be responsible for the care of all newborn babies who need extra support shortly after birth, should be alerted.

The RCOG said that women with chickenpox should breastfeed if they wish to and are well enough.

Guideline co-author Professor Patricia Crowley described chickenpox as rare in pregnancy, adding that many adults are immune to it after having had the virus when they were younger.

RCOG guidelines committee co-chairman Manish Gupta said: "Chickenpox is very contagious so it is important that women are aware of the symptoms and the necessity to seek medical attention promptly.

"It is also vital that clinicians are aware of the increased morbidity associated with chickenpox in pregnant women and ensure that the woman receives the best possible care.

"Women may worry about passing the virus on to their baby, however this is quite rare and depends on what stage of pregnancy the virus was transmitted."

Louise Silverton of the Royal College of Midwives welcomed the revised guidelines, saying: "This is sometimes seen as a minor illness but it can have serious consequences for pregnant women and developing babies and needs to be managed effectively.

"Pregnancy can be very confusing for women as they are taking in a huge amount of information and we need to ensure that women know what to look for without causing overload.

"Women are already recommended to have vaccination against flu and pertussis and if not immune after pregnancy to have the rubella vaccine."