1. Health
Send to a Friend via Email

Poll: When Does a Pregnancy Begin?

By March 11, 2009

Follow me on:

With various current events in the media lately, there are a lot of debates flaring up again over embryo rights and the definition of when life begins. And after reading a study a reader of this site sent to me the other day, I realized that these issues have a connection to the definition of a miscarriage. Usually when people are debating abortion, they argue over questions such as when life truly begins, and the viewpoints can put the start of life anywhere from fertilization to the moment of birth. No one really agrees, thus people argue over whether an early pregnancy involves a baby or a "potential baby," etc.

But putting aside the question over the start of life, there's kind of a similar conundrum in the question over when a pregnancy truly begins -- and the difference of opinion could lead to misunderstandings over what constitutes a miscarriage. The traditional 40-week pregnancy calendar confusingly starts counting weeks of pregnancy at the start of the menstrual cycle, which is two weeks before the sperm even meets the egg (so you're "two weeks pregnant" already when you conceive). Then there's another week where the fertilized egg is floating through the reproductive tract before it implants in the uterus, which is when your hCG levels start to rise. And the implantation process sometimes goes awry, perhaps causing a slight rise in hCG levels, but then the woman's menstrual period comes right on schedule or a few days late (a chemical pregnancy).

So one wonders: when does the pregnancy actually begin? Is it from the time of fertilization? Implantation? Or from the time that the pregnancy becomes "clinical" as opposed to "chemical," even though the latter does involve a fertilized egg and rise in hCG?

I've noticed that people tend to have different opinions on this and it can have some ramifications for the definition of a miscarriage. Despite counting weeks of pregnancy from the start of the menstrual cycle, most doctors seem to define pregnancy from the point of implantation (the point at which you can detect hCG), and thus to them, anything that interferes with implantation is merely preventing pregnancy rather than causing a miscarriage. But I've noticed that a lot of moms seem to think otherwise, and many will consider any failed implantation (even a failed IVF cycle) to be a miscarriage.

And thus you end up with disagreements on numerous questions, such as whether birth control pills cause miscarriages. Researchers will tell you they don't, because there's no real evidence that they will disturb an established pregnancy or increase the risk of miscarriage in a future established pregnancy. But it's also commonly believed that birth control pills partly work by making the uterus inhospitable to a fertilized egg. Some people might say that meant they cause miscarriages, but it depends on whom you ask.

What do you think? When is a pregnancy truly a pregnancy? I'd be interested to hear your opinions.

March 11, 2009 at 4:05 am
(1) Rachel says:


I said at implantation, but that doesn’t mean someone who finds out their pregnant before implantation (however that would happen) takes place is not having a miscarriage. The reason I said at implantation is because during IVF, when they transfer the embryo, fertilization has already taken place — but unless the embryo implants itself in the uterus, you don’t get pregnant, the cycle is not a success. You get your period when you would expect it (perhaps a few days late from progesterone shots, but not because of a “pregnancy”.)

On the other hand, I don’t want to discount those who feel emotional pain over the loss of failed cycle. I mean, during IVF, for example, while the embryo not implanting isn’t considered a “miscarriage”, it still is a very painful things to go through. Especially when you consider the potential for pregnancy was *so* close…

~ Rachel

March 19, 2009 at 3:21 pm
(2) Mariah says:

Well, I think it’s at implantation too. If you think about it, you’ve never heard of a pregnant bird, right? That’s because she holds the sperm in her for however long, uses it to fertilize a developed egg, and then lays it. Later, the baby hatches from the egg and never was the mother considered pregnant. For humans, the developed egg is fertilized in the fallopian tube. About two weeks later, it *hatches* and then attaches itself to the uterine lining. That’s implantation, that’s when humans are considered pregnant (unless you’re a doctor and you count it from the first day of your last period), and that’s one of the things that separates our reproductive system from most egg-laying reproductive systems.

My point is that we’re not pregnant until the fertilized egg hatches, implants itself, and begins to get nutrients from our bodies.

March 22, 2009 at 5:50 pm
(3) angel says:

I agree 100% with the two lady!! bcuz if you look at it anything could happen in the process of implantation and until the eggs safely attach itself to the uterine wall we are not sure whether we are pregnant or not!IMPLANTATION is the First Step to being Pregnant!!!PLEASE understand i’m not trying to offend anyone. just think about it,doesn’t it make alot of sense!!!

April 10, 2010 at 6:09 pm
(4) Melinda says:

I have to say at conception. That is when the genetic material comes together to make a seperate being, as defined by DNA. Whether or not you know your pregant is irrelevant to being pregant. I knew a woman who was 4 months along before she missed a period and suspected she might be pregant. A miscarrige can happen at any point in the pregnancy. That an embryo doesn’t implant doesn’t mean it didn’t exist.

Leave a Comment

Line and paragraph breaks are automatic. Some HTML allowed: <a href="" title="">, <b>, <i>, <strike>

©2014 About.com. All rights reserved.

We comply with the HONcode standard
for trustworthy health
information: verify here.