How can you not know that you’re pregnant? Missed periods, nausea, ballooning belly — then all that tickling and kicking and shoving inside you.

Well, quite easily, as it turns out. Studies in Germany and Ireland have revealed that one baby in around 600 is born to women who were apparently unaware of their pregnancy until very late or when they were actually in labor.

Beth Jeffrey discovered she was 25 weeks pregnant a week before her 24th birthday.

“I went to see my general practitioner, who examined me, told me I was pregnant and ordered a scan to establish dates as I had no idea when I might have conceived,” she said.

Jeffrey was completely caught off guard. She said she had no symptoms.

“I’m not the skinniest person in the world, but there was no weight gain, I did have irregular periods, but put that down to the stress of starting the new job and I’d felt fine.”

It’s not just young, first-time mothers who miss the signals. It happened to the novelist Maggie Alderson and it happens to other women in their 40’s more often than you would think.

“I had given up any hope of getting pregnant,” said Alderson. “And at 42 after missing two periods I assumed I was having the menopause. I’m afraid I was pretty ignorant: I just thought your periods stopped and that was that.”

It was her mother who suggested that she should get a pregnancy test.

“Lord knows how much longer I might have gone otherwise,” said Alderson, whose daughter Peggy is now 7.

Even women who already have children and you’d think would recognize the symptoms of pregnancy are fooled. Amanda Morgan, who already had two sons, was 40-years-old and had no idea she was pregnant when she gave birth to daughter Caitlin.

“I’d just been to the doctor, who said I was experiencing the classic signs of the menopause,” she told a BBC reporter. “She then booked blood tests at hospital to check my hormone levels.”

Morgan returned home after the appointment and complained of feeling exhausted. She had gone to the bathroom when she felt a crippling pain, and minutes later Caitlin was born.

“It was a complete shock to me," she said. “I’d had no morning sickness or tiredness and had absolutely no bump at all."

There is relatively little research in this area but what studies do exist are always couched in terms of “denial” or “concealment” of pregnancy, implying that at some level these women do know they are pregnant but choose, consciously or unconsciously, not to acknowledge it.

“The absence of many physical symptoms of pregnancy, inexperience, general inattentiveness to bodily cues, intense psychological conflicts about the pregnancy, and external stresses can contribute to the denial in otherwise well-adjusted women.” A German study reported.

An 11-year study at University Hospital in Cardiff noted a preponderance of concealed pregnancies in winter when women could disguise their bumps with layers of clothing.

So what is going on here? Are we to assume that every woman who claims not to know she is pregnant is actually fooling herself and everyone else? Not necessarily, according to Sue Macdonald, of the Royal College of Midwives.

“An unplanned pregnancy can cause extreme anxiety and anxiety produces a closed mind which refuses to recognize symptoms. But there may be another explanation: some bleeding in pregnancy which women think is a period or they might be carrying a bit of weight, or have very tight tummy muscles so the bump is not apparent.”

But what puzzles most of us is how a woman can fail to feel her baby move.

“Early on a baby’s movement feels like weird bubbles and flutters which the mother may not understand,” said Macdonald. “Later there is more of a shifting around which may be interpreted as irritable bowel syndrome — this is not uncommon. And some babies just don’t move much at all.”

None of the studies comes up with a clear profile of the type of woman likely to deny, conceal or just not recognize her pregnancy, which makes early intervention almost impossible.

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