When Does Pregnancy Begin?

It should be a simple, easy answer, shouldn’t it? But it’s not. It’s complicated by tradition as well as politics.

Some time ago, I was arguing on an abortion blog, and some guy said something about, “You pro-lifers say that pregnancy begins much earlier than doctors do!” Well, he’s sort of right but mostly wrong.

Many people, myself included, are strongly pro-life, and count life to begin at conception — which is when embryology textbooks also say is the beginning of human development. Before the mid-1960s, conception was generally considered to be the start of pregnancy, but with the politics of abortion looming large (not to mention birth control pills), the medical community changed the term, saying that since we didn’t really know for sure when conception took place, pregnancy shouldn’t be considered to have begun until the fertilized egg actually implants in the lining of the uterus. This allowed doctors to prescribe drugs and hormones which would interfere with implantation, but not to break laws against abortion. It also allowed pro-life doctors and pharmacists in good conscience to prescribe and dispense hormones which might allow ovulation, but have as a “back-up mechanism” keeping the blastocyst from implanting. Many people (such as myself) are uncomfortable with this, and would consider it to be abortifacient. Technically, it’s not, because it’s not considered to be an abortion until the blastocyst has implanted and develops into an embryo.

So, that was the guy’s point — that we put the start of pregnancy back at conception, which is up to a week before implantation, which is when ACOG declares pregnancy to officially begin.

But it’s not as simple as that. Because in dating a pregnancy, and saying that your due date is at 40 weeks, with term being anywhere from 37-42 weeks, they’re not dating that from implantation, nor even conception. Rather, pregnancy officially starts on the first day of your last menstrual period (LMP), which is usually about 2 weeks before ovulation. So, on one hand, your pregnancy is considered to have started two weeks before even the most ardent pro-lifers will say that pregnancy begins, and about three weeks before implantation, which is when “pregnancy” is defined as starting, for purposes of labeling something an abortifacient.

Why? A German obstetrician back in the 1800s decided that since women’s menstrual cycles occur monthly like lunar cycles, on a 28-day cycle (average), then pregnancy should take ten “lunar cycles”, or ten periods of four weeks, or 40 weeks. But there are two problems with this — first, 40 weeks from conception would make the average or typical pregnancy last to what we currently call 42 weeks. While many women would naturally go this long (and most without a problem), most women would have given birth by this time. The second problem is, that ovulation is not necessarily a memorable or noticeable event, but menstruation certainly is. So, presto change-o, pushing the start of pregnancy back to two weeks before conception, or the start of a menstrual period, solves both problems. While keeping intact the precious, preconceived notion [pun not intended] and dogmatic assertion of a German doctor. Above all else, unsubstantiated claims must be kept intact, despite actual evidence to the contrary, as long as a doctor came up with it!

Yes, I’m being sarcastic. 😉

This makes things a little difficult, sometimes, when thinking about stuff that happens in the early days of pregnancy — some books, websites, etc., will date the pregnancy as starting at conception, while others will date it starting at LMP. So, whenever I hear something about embryo development, and things like “the heart starts beating at 5 weeks,” I wonder, is that 5 weeks from conception, or 3 weeks from conception? After you get out of the first trimester, it gets easier, because it’s pretty standard to switch to “gestational age” (i.e., from LMP) in full. I remember one book I read when I first was pregnant that was a pregnancy picture book, and they did this — in the first trimester, the pictures were all dated from conception; but in the second trimester, the pictures were dated from LMP. I wouldn’t have noticed, except they drew attention to it; I suppose as a way to avoid having the first two weeks worth of pictures being blank? I always kinda wondered, where did those two weeks go? 🙂

Also, as an aside, I know at least one woman whose pregnancy officially started when she was still a virgin, thanks to pregnancy starting on her LMP, a week or two before her wedding, and she got pregnant on or soon after her honeymoon. It’s things like that that make my “OCD meter” go haywire! If we’re going to put things in nice, neat little packages, let’s make sure they fit, okay?


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13 Responses

  1. Kathy, If your egg is fertilized but never implants in your uterine wall, and you have your next period as normal, were you ever pregnant? Also, is the beginning of the pregnancy the same thing as the beginning of life?

    • That’s exactly the controversy, and it depends on your point of view.

      If pregnancy begins at conception, then, yes, you were technically pregnant. I explored the idea a bit more in this contemplative post I wrote some time ago, when I was a few days late, and I wondered if I may have been pregnant and was having a very early miscarriage — so early that it appeared to just be a late period.

      Sometimes I think about Abraham Lincoln’s joke: “If you call a tail a leg, how many legs does a dog have? Four — calling a tail a leg doesn’t *make* it one!” So, the change in definition of the beginning of pregnancy does not change the physical reality, one way or the other — it’s just a term we have made up to try to categorize and classify and structure and make things fit into nice, neat little boxes — sort of like the various stages of human development — there are different terms for all different stages, from the single-celled fertilized egg, to a multi-cellular pre-implantation structure, to when the blastocyst implants, and then becomes an embryo, and then a fetus, and then a newborn, infant, toddler, etc. It’s all the same entity, just at different stages of development. Just as English has dozens of different words and phrases that can be employed to mean “off-white” (beige, eggshell, cream, etc.), which all look practically the same to most people, and different people might look at one shade of off-white and use different terms to mean the same thing. Right now, pregnancy is standardized to mean one thing; but had history taken a different turn, it may have meant something a bit different. [For instance, at least one woman I know got pregnant on her honeymoon or very soon thereafter, so for gestational dating purposes, her pregnancy “officially” started before her wedding, when she was still a virgin. Which reminds me, I need to update the post to include this little story, to show how weird the whole “dating from LMP” can be.]

      So, technically, because of the standardized definition of ACOG, in answer to your question, no, you were officially not ever pregnant. Although a new life did begin and end inside you. But the reality is (and I look at this a bit more in the post I linked to), thanks to early pregnancy tests, it is possible to get a positive pregnancy test, and still start an apparently normal period right on time (or perhaps just a day or two late), because you were actually pregnant (by anyone’s definition), but it just didn’t “stick,” for whatever reason. You can also read in the comments a post by Michelle, a midwife, who says in part, “If the high [basal body] temperatures persist for 16-19 days [after ovulation], you can absolutely conclude that pregnancy has occurred…. As a rule, a “luteal phase” that lasts 18 days, causing 18 days of sustained, high basal temperature, indicates pregnancy.”

      In answer to your second question, since pregnancy officially begins at implantation (for purposes of defining what an abortion is, and saying that chemical birth control is not ever abortifacient; not for purposes of dating a pregnancy, which is pretty standard at starting about two weeks prior to conception), then, no, the beginning of pregnancy would not be the same thing as the beginning of life — a new life begins when a sperm fertilizes an egg, the nuclei fuse and create a genetically new and unique creature. Then, since it already is alive (being the union of a living sperm and living egg), it manifests that life by growing and dividing, and continuing along the path that every human takes, unless something interferes with it. A dead thing doesn’t grow. Since a fertilized egg obviously does, that is “proof of life.”

  2. I used to work for Planned Parenthood, and one of my pet peeves about the pamphlets handed out by the anti-abortion demonstrators was that they were always mislabeled. A picture of a 8 week embryo (by gestational age) would be labeled “10 weeks” (by LMP)–of course the average layperson doesn’t know the difference. I always felt like the anti-abortion movement should be confident enough to stand on the truth as they see it, without manipulation of their audience.

  3. lesbonurse, I wonder if you ever considered that maybe they were not trying to mislead people, but were assuming that their audience was counting from LMP, too? If I’m talking to regular laypeople who, as you said, don’t know the difference between the two, isn’t it reasonable to give the age by LMP? If a laywoman is pregnant, she knows she is 10 weeks pregnant. She might know that her baby is 8 weeks old, she might not. Even if she *knows* that, there’s a good chance that she doesn’t think about it like that — she just thinks that she is 10 weeks along. And there’s a good chance that if you show her a picture of a baby labeled “10 weeks,” she’ll understand that it’s a baby the same age as hers, not think it’s a baby two weeks older. At least, that’s what *I* would think, being a layperson myself.

    Also, even if they were purposefully giving the age by LMP in an attempt to manipulate their audience, they’re doing a crappy job. Going by LMP as opposed to gestational age makes a baby seem OLDER. Which makes it seem like it took LONGER to get to that point of development than it really did. The whole point of those pictures is to say, “Look how amazingly formed and advanced this baby is even at such a young age!” If anything, if you were pro-life and wanted to manipulate your audience with photos like that, you’d do it by giving the gestational age when people expected you to count from the LMP, making the baby appear younger than he really is.

    Kathy, I was aware that the official “start” of pregnancy had not always been implantation, but I never thought about the fact that pregnancy is counted starting from LMP. It’s all so very arbitrary!

    Honestly, I don’t think our arbitrary definition of when pregnancy starts should have much of anything to do with whether abortion or birth control is ok. For one thing, obviously we all feel free to move that starting point around based on our own needs, and even use different definitions in different contexts. For another, I tend to think that “pregnancy” is more about me, and the changes in my body as a *result* of that new little life that has already formed inside me. When we put the focus on when “pregnancy” starts, we lose focus of when that life starts. It doesn’t matter when *my* period was, when the baby attached itself to *my*uterus, or whether a test could detect hCG in *my* urine. What matters is when that *life* first comes into being. Everything else is just secondary.

    • I love the last sentence, really makes the point well. If the pregnancy is about the BABY, obviously it begins when the baby’s life begins, regardless of what is up with mom’s body. If pregnancy is about the mom, then when it begins is completely subjective and doesn’t have much, if anything, to do with the baby.

  4. Agree with you wholeheartedly. Also, there was some episode of Oprah in which abortionists admitted to life beginning at conception. You might be able to find it searching her website.

  5. I recall when I had an early miscarriage at 5 weeks, the nurse called to say the numbers were dropping and “no baby is there anyway.” Uh, okay, to a regular person who is having a miscarriage after a 16 week IUFD, I lost it. I asked if the genetic material was different than mine? The nurse replied, “yes.” I then said, “it’s a baby then.” My OB clarified when I told her and she said, “it was still your child.”

  6. My husband and I are both big time pro-lifers who study the debate and science behind it extensively. Since doctor’s change their mind (once any doctor would tell you life began at conception, then it was implantation (solely due to pressure from drug companies and the pro-abortion front), now many doctors will say life doesn’t begin until ‘viability’ or until birth, or until first breath) we always go with the science of it. According to the rules of biology (and STILL listed in even the most anti-life biology books) life begins at conception when a unique DNA code is created and the new human meets all the criteria of life (growth, excretion of waste(also called production), reaction/defense, and consumption). Regardless of what anyone with a political agenda says, the biological scientific fact is that human life begins at conception. As for the ‘early miscarriage’ question, if you read a pregnancy book printed before the ACOG changed their position on conception vs implantation, most will say that many pregnancies end in miscarriages before the mother even knows she is pregnant. Books from the time make the point that not all pregnancies are viable and these early miscarriages are the bodies way of ending a non-viable pregnancy. (One of the requirements of life is reaction/protection. Between conception and implantation the new baby secretes a hormone so that the mother’s body won’t attack it as a foreign object. It was assumed, although no way to prove, that many of these early miscarriages were babies who failed to secrete these hormones.) In all of the pro-abortionist’s political clout clouding the issue many simple facts about pregnancy that used to be well know and accepted is being left out of the current books and medical information because people are more concerned with stepping on the toes of a political giant (planned parenthood comes first to mind) than providing woman with full information about their pregnancy and new baby (even worse current medical research is being burried, ignored, or hidden from woman because it underminds the abortion agenda). I know its a ‘cliche’ but “If its not a baby, you’re not pregnant” and, as a follow up, if its not alive why do you have to “terminate” it? As an aside, I dislike the whole gestational age vs LMP age. It makes no sense to count the pregnancy from before it begins, and it confuses woman (even ones within the medical community) when books/pictures/etc are refering to babies as ‘X weeks’ and doesn’t specifically say ‘gestational age’ or ‘LMP age’. And it doesn’t just get confused in early pregnancy, if you try to find info on very early premature births, they are also listed (sometimes without mention to it, sometimes making the point) sometimes by gestational age an sometimes by date of mother’s last period. I think a lot of that also has to do with pressure from the abortion camp. If they are pushing woman into abortion by saying their baby isn’t really ‘alive’ until its viable which is usually considered 24 weeks, a preemie who lives before that date underminds them. Saying a baby survived at 21 weeks is bad enough, actually admitting that baby was 19 weeks gestation age is a lot worse! That’s before a woman might even feel movement, and, while its certianly rare, babies born at that age have survived! (If anyone wants it, I have done research and have specific dates/places of birth and names of some 19 week old gestational age survivors)

    • Jessica, thank you for this reply. I would like to have the information you have, of the 19 week babies who have survived. I know of Amilia Taylor from Florida, but she’s considered to be 21w6d gestational age. According to this policy statement, “gestational age” is defined as the time from the woman’s LMP (last menstrual period) — so it starts about two weeks before she ovulates. But the statement is in response to frequent misuse, ill-defined uses, or undefined uses of the various terms, so it’s an attempt at standardization. They use the term “conceptual age” to mean from the time of conception (which they leave fuzzy as to whether it is actual conception or just implantation), but say it is “inaccurate and should not be used.”

      So, unless I am mistaken, Amilia Taylor, born at 21w6d gestation was actually 19 weeks from conception (fertilization, the joining of egg and sperm).

      As the old-timers would say — “what a pretty kettle of fish this is!” The more I try to explain, the more muddled it seems to become! 🙂 Like I said — it sets off my OCD. 😉

      • Okay, sorry, my bad, I used ‘gestational age’ when I meant to use ‘fetal age’! info: Kenja King born in Orlando Fl, Nov 11 1985 at 19 week fetal age and James Gill who was in the 1989 Guiness Book of World Records as the youngest surviving preemie at 145 days early. (couldn’t find out if the GBoWR was using a 280 day gestational pregnancy, which would put baby just over 19 weeks or if they were using a 266 day fetal age pregnancy, which would make James Gill born just over 17 weeks) Two surviving infants born at 18 weeks fetal age are mentioned in the book “Abortion Questions and Answers” Authored by JC Willke MD. A website authored by him lists some specifics about other early babies here: http://www.lifeissues.org/connector/2007/Apr07_YoungestPreemie.htm
        this was the best info I could find during a recent debate with a family member. It was interesting to me, and I hope to find that book one of these days. Hope it helps. And, I agree, sounds like Amilia Taylor was also a 19 week fetal age birth.

  7. Kathy, thanks for your detailed and thoughtful answer. These issues are very confusing. I always assumed that pregnancy is counted from LMP because that’s the last date we know for sure that you were not pregnant, so as to standardize the counting, because we can’t really be completely sure when exactly you got pregnant. It seems to me, though, that life and pregnancy can begin and end at different times. For example, if you go through IVF, conception (and therefore by your definition, life) occurs way before pregnancy, no? If you have a miscarriage, it may be days or weeks before your body expels the fetus. You’re still pregnant, even though the life has ended. Or if you have an IUFD later in pregnancy, you are still pregnant even though your child has died. I’m not sure what are the moral/ethical implications of all this, but these are clearly examples of life and pregnancy not lining up exactly.

    • Nora,

      That’s right — I would assume everyone would agree that a woman was still pregnant, even though her baby had died, before she had a miscarriage or stillbirth. And I don’t know anyone who would think that a woman who had several embryos in storage at a fertility clinic was pregnant, when not one of them was inside her!

      To make matters even less clear, just as there is a “range of normal” for things like length of menstrual cycle, or at what age a girl first starts her period, or when a woman goes through menopause, or when a baby is due (term ranges from 37 to 42 weeks of gestation, or 35-40 weeks post-fertilization), so there is a “range of normal” for when an egg is fertilized (at some point within 24 hours, because that is as long as it lives, unfertilized), and also for how long it takes for the fertilized egg to implant — up to six days. [Sometimes I wonder if these things alter how long an individual pregnancy would naturally last.] But two women could have the same LMP, but ovulate on different days; and even if they ovulated on the same day, one could conceive 20 hours earlier than the other; and one of the blastocysts could implant even a few days earlier than the other — all with the same LMP!

      But, without invasive procedures (I’m envisioning a tiny scope or perhaps a vaginal ultrasound) keeping an eye on everything 24/7, there is no way of knowing exactly when these things occur, aside from IVF procedures.

      LMP is a good effort at standardization… as long as the woman is regular, and does not have months or even years without a period, prior to pregnancy. I know of several women who have gotten pregnant before ever getting their periods back from being pregnant a prior time. Imagine the looks they must get, when their “LMP” is 12 or 15 months ago, although their current pregnancy would be dated 5-10 weeks, or whatever! So, sometimes, it can be pretty useless. 🙂

      Yes, moral and ethical implications aside — life and gestation pregnancy frequently do not “line up exactly”! That’s a good way of putting it.

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