How can a woman possibly be pregnant and not realise?
It can be a strange combination of circumstances where a woman has a tiny bump, no morning sickness and continues to have light bleeding every month, but midwives and maternity experts have told the Huffington Post UK that many women simply explain away their symptoms as weight gain, indigestion, menopause or puberty.
The situation where a female soldier gave birth at Camp Bastion, Afghanistan, without realising she was pregnant, is extremely rare, but not unheard of.
A soldier has given birth at a camp in Afghanistan
Belinda Phipps, chief executive of the parenting charity NCT, said it could be easier to miss a pregnancy in a highly stressful situation, like being on the front line in Afghanistan.
"When you're a soldier, it's a life or death situation, in that situation, your body prioritises your own survival, not that of the baby. Your body thinks 'I need to keep you alive first and foremost'.
"And you can be so focused on yourself you don't realise the pregnancy. Quite often people under that much stress will miscarry."
Angela King, a senior lecturer in midwifery at Northumbria University, told the Huffington Post UK: "It's very uncommon, but in 38 years as a midwife I have seen it happen to women of all ages, from teenagers to middle-aged.”
“They explain away the symptoms, they may get a bit of bleeding and interpret it as a period. If the baby is moving, they might think it is wind. If they are older, they think it is the menopause."
Peggy from Mad Men did not realise she was pregnant
Giving birth without realising you are pregnant is highly stressful for mothers - and has often been used as a dramatic storyline for soaps or TV dramas.
Vicky, in BBC Radio 4's The Archers got a shock when she realised she was pregnant, aged 47.
Peggy Olson on Mad Men got progressively fatter after her affair with Pete Campbell, and had a shock when she gave birth to his child at the end of Series One, but gave the baby up for adoption.
For some though, the shock has to quickly become reality.
Melanie Hannen's daughter Lauren had put on half a stone and was on a diet to lose the weight. She told the Daily Mail: "At first I thought Lauren probably had a tummy bug, but it was soon clear that she was in incredible pain and this was no upset stomach.
"I called an ambulance, but even as I was on the phone to the 999 operator, I could see Lauren on all fours and immediately realised she was having a baby."
She said Lauren was "white with shock and rooted to the spot."
Lauren, who now lives with her baby Lily's father Ben, said: "I was numb for days. I wanted children, but not for at least another ten years.
"Now that Lily is here, though, I can't imagine not being a mother."
Some women remain blissfully unaware they are pregnant - explaining it as weight gain
Jacque Gerrard, Director for England at the Royal College of Midwives, said: "In my experience, mostly it is young women who are in denial and have concealed their pregnancy, not admitting it to themselves.
"For older women, it's actually a genuine shock and surprise. Sometimes it is childless women in their 40s, given up all hope of having children, not using contraception and then a baby arrives. That's a shock but a good kind!"
Phipps told the Huffington Post UK: "It's much more common in very young girls or in older women, who explain it away as the menopause.
"It can be very difficult to adjust to, becoming a parent is a transition which doesn't happen overnight, the same as becoming an adult when you're a child.
"Most mums have nine months to get used to that new identity, to be able to confidently say 'I'm a mum'.
"But if the baby is a surprise, women really need to talk about it a lot, it's a huge readjustment. They have to suddenly change their lives, cancel plans to go to university or retire.
"You can't do that anymore, and many will be angry and depressed."
King said new mothers tended to experience a huge range of emotions: "In my experience, it's usually shock followed by complete delight and concern for the baby's welfare but it is highly dependent on social circumstances.
"Have they had an affair? Are they in a relationship? Do they have a supportive family? Post-natal depression is very closely linked to these circumstances.
Midwives and doctors will closely monitor a mother and baby where the birth is unexpected, and the labour will be immediately deemed "high risk".
"There's been no screening pre-birth so we have no idea of the risks of the pregnancy to mum or baby, we have no idea of the health of the baby," Gerrard told the Huffington Post UK.
"So the immediate focus is medical care of mum and baby. I know Camp Bastion has flown out a specialist team of people to care for the female soldier and her baby, and will bring them back to the UK as soon as it is safe to do so.
"The Ministry of Defence will really look after her and the new baby and keep them safe.
King said: "There can be problems if a woman has smoked or drunk alcohol during the pregnancy, we can assume that will have some effect on the baby, and there's some evidence that women who do not have any antenatal care will have premature or smaller babies.
"But with a soldier, we can assume she had a healthy lifestyle, and that will be very important for the welfare of the baby."
"Actually she's likely to be incredibly fit and healthy, not smoking or drinking, exercising and eating healthily," Gerrard said. "That will be very much in her favour."