I understand that miscarriages and “spontaneous“ abortions are fairly common in the second and third trimesters, but how common is this prior to having knowledge of the pregnancy? Clearly, the likelihood of a late, “heavy” period being the result spontaneous abortion would depend on the regularity of the woman’s cycle (as well as her recent sexual history), but would a delay on the order of several days generally indicate that a pregnancy has been terminated? Could such an event really go unnoticed? With a reported incidence of >50%, is spontaneous abortion of a pregnancy really the rule, not the exception?
how on earth would some one know? I’m personally not in the habit of retreiving the ‘flow’ and having it analyzed.
I recently heard an interview with Art Caplan, director of the Center for Bioethics at the University of Pennsylvania. He was discussing the issues of using embryos for stem cell research. If I recall correctly, he said that only 25% of fertilized eggs are implanted and become fetuses. So it depends on what you mean by “spontaneous abortion.” If you are referring to embryos, then it is the rule rather than the exception. If you are referring to fetuses, I don’t know, but I doubt that a spontaneous abort is more common than not.
wring IIRC most of the info has been gathered as a result of IVF programs. Those pregnancies are very closely monitored. How well that info correlates with populations with normal fertility is of course debatable.
I’ve seen figures which suggest 50% of embryos miscarry very early in the pregnancy. Most pregnancies fail in the first trimester, not the second or third. Pregnancies lost in the third trimester are usually referred to as stillbirths, not miscarriages.
It is possible not to be sure whether it is an early miscarriage or simply a heavy period prior to about 6 or 7 weeks. At ten weeks, it is noticeable usually as the cramping is very heavy and the flow is different. A D&C is usually recommended past about 8 weeks.
thanks for the info - I’d be suspicious of extrapolating data from IVF to the general population (certainly not a random sample, nor a large one if memory serves). The above is what I was getting at. I’d suspect the average female upon being a few days late, then her period starting would simply say either “oh good” or ‘oh damn’ (depending on her individual circumstances) vs. attempting to discover if there was an early stage pregnancy.
I was hoping an actual embryologist would take a crack a this question.
Oh well.
The 25-50% figure for spontaneous abortion in the first trimester dates from well before the advent of IVF. I’ve seen it in books from the early 70’s, so it probably is based on even earlier “rabbit test” data.
Squink
you wouldn’t get an absolute answer from an embryologist in any case. We don’t really know an absolute answer to the question.
Rabbit tests wouldn’t be all that much use to detect very early pregnancies because they IIRC weren’t sensitive enough to pick a 6 week pregnancy. I’m feeling too lazy to walk downstairs and check my midwifery texts.
Wring
even if our putative mothertobe were doing pregnancy urine tests from possible conception, it is feasible for someone to be pregnant but the hormone levels never rise to detectible levels. I don’t think most of us are going to shell out for expensive tests unless we’re obsessed with getting pregnant or alternatively obsessed with not getting pregnant 
I’m glad those days are behind me.
50% in the first trimester, according to www.obgyn.net.
1994 data, so I assume “rabbit tests” were not involved.
The 50-70% rate is not for spontaneous abortions, which is what the medicos call miscarriage, but “total loss of conception [in the first trimester]”. This includes anything that prevents a zygote from becoming a fetus (at about the twelfth week of pregnancy). An unknown, but presumed significant, number of fertilized eggs simply never get to the uterine lining in order to implant; they pass out of the body unnoticed with the woman’s next menstrual period. In medicine, a pregnancy begins when the zygote implants, not at conception, so when a zygote just passes straight through the uterus it’s not called a miscarriage.
I’m more than a little skeptical about the claims of women who “knew” that their three-days-delayed menstrual period was really an early miscarriage. From my experience with an on-line preggo support group, these are often women who are trying very hard to get pregnant, and were sure they had pregnancy symptoms the morning after the ovulation predictor kit said “go for it”. (Sperm and egg, meanwhile, have barely been introduced.) Three days just isn’t much time. The embryo is growing at an incredible rate, but a 100% increase from the size of a pinprick is still unimaginably tiny, and there just isn’t much to miscarry yet. The amount of cramping and bleeding isn’t going to be significantly different from any other cycle. So… maybe it’s a very early miscarriage, maybe it’s just a late period with an overlay of repeated disappointment.
At the time of my miscarriage, a hospital gynecologist said to me that between 1 in 10 and 1 in 4 pregnancies ended in miscarriage, depending on which authority you believe. It is certainly true that it happens more often than many people know. But let’s not over-dramatize… it’s not a miscarriage every time a couple who are trying to conceive a baby fail to do so.