The Ministry of Defence have released a statement saying "Mother and baby are both in a stable condition," following the birth on Tuesday in Camp Bastion, Helmand province.
The woman, a Royal Artillery gunner who has not been named by the MoD, only learned she was about to give birth after complaining of stomach pains. The child was conceived before she arrived in Afghanistan in March. The baby was born five weeks prematurely.
In a statement, the MoD said: "It is not military policy to allow servicewomen to deploy on operations if they are pregnant. In this instance the MoD was unaware of her pregnancy."
A specialist paediatric team from Oxford's John Radcliffe Hospital is to fly to Afghanistan in the next few days, the statement added, "in order to provide appropriate care for mother and baby on the flight home".The baby was born five weeks prematurely.
So-called denied, or undetected, pregnancies are rare but in some cases women do not show a bump and continue to have periods for the duration of the pregnancy. Research in Germany in 2002 found 25 out of 475 mothers did not realise they were pregnant until they went into labour.
At that time Mary Newburn, from the National Childbirth Trust, explained that some people simply refused to admit to themselves they were pregnant. Some younger women were not aware of the significance of the changes occurring to their bodies. "Most of us put on two or three stone (28-42lbs) while we are pregnant and by the end of pregnancy feel very much as though it is dominating our entire being, so it is difficult to imagine how anybody could get to the later stages of pregnancy and not realise it. But pregnancies do vary enormously, and particularly for bigger women the amount of weight they put on is less proportionately."