Pregnancy tests make us think pregnancy is like an on-off switch: two lines and you’re having a baby, one line and you’re not. But pregnancy can be a much scarier place, an uncertain grey area between conception and implantation when a tiny bundle of cells must try to settle in the womb and may not succeed.

I had my first child at 29; three years later, when we decided to try again, it all got much more complicated. Over the space of the next three years I had eight early miscarriages, all before nine weeks. The first couple I wrote off as normal – and early miscarriage is completely normal. But soon, becoming pregnant signalled the start of a grim routine.

By my sixth miscarriage, I could tell I was pregnant before I took any test: I could feel implantation, I knew when I was feeling the flood of hormones that implantation triggered. And I could tell when I was miscarrying, even before the spotting began, when I felt my hormones seep away as each pregnancy failed.

But to establish for certain that my pregnancies were failing, I had to return, time and again, to the early pregnancy unit of the local London hospital for an ultrasound to make sure.

Early pregnancy units are filled with rows of silent couples holding hands; places where the waits are long and the stakes are high. Some women are obviously in physical pain; others are spared everything but the grief. Our partners, inevitably, wracked with worry but ultimately useless.

A scan in those early weeks will determine one of three things: that the pregnancy has failed; that the pregnancy is failing to thrive for the gestational period but you might have got your conception date wrong and it might still be OK; or that the pregnancy looks OK. I was always told to come back in a week to establish for sure whether the pregnancy was failing or not.

For me those weeks in between scans were the worst: after waiting months to become pregnant, and then waiting hours in those rooms full of other people’s sadness, I would always be sent home for a week to wait and see again. It left me desperate. It was too hard to carry on as though nothing was wrong for a week, over and over again, feeling half-pregnant and not knowing what the future held for me or the baby we wanted. Not knowing whether a pregnancy was failing became more emotionally trying than knowing that it had failed – even if knowing meant that I wouldn’t be pregnant any more.

I learned, too, how you could wangle an extra scan if you turned up at a quiet moment before your next appointment, asking just a little reassurance. But I played that card one too many times and was told firmly by a kind nurse – who by that point knew me by name – to go home and just wait. There was nothing anyone could do.

Today, a study in the British Medical Journal suggests that the standard one-week wait between scans might not be long enough to know for certain whether the pregnancy has failed or not. Instead, it is now suggested, women should go home for two weeks before having another scan. The alternative is a 2% false positive rate – meaning that in two out of every 100 cases that a woman is told the pregnancy is failing, the doctors are wrong. If those two women in every 100 choose to have a termination rather than let the pregnancy end naturally the women might be aborting potentially viable foetuses.

But as desperate as I was at that point to have a child, I don’t know whether I could have stood another week of not knowing, given the relatively low risk of the doctors getting the diagnosis wrong. I already had a child, and didn’t want to be uncertain and sad any more. The recommendations do little to take into account the other 98 in 100 women who will wait another week and convince themselves it’s all OK, only to be disappointed again when the result is confirmed.

Eventually we gave up trying for a second child: I took a more stressful job, we booked some holidays and felt very, very thankful for the amazing child we had. But, of course, within a month, I was pregnant again. For some mysterious reason, this last time, it worked.

I never found out why I had so many miscarriages – most couples don’t. For something as common as having a baby, there is so much we don’t understand about pregnancy. But then, when my son was born, what we don’t know didn’t really matter any more.