Arizona is advancing the front line of the war on women. Every week, or so it seems, there are increasingly dystopian bills floated around the state House and Senate. Senate Bill 1359, which hopes to protect doctors from wrongful birth suits, the narrowly defeated no-sex-please-we’re-from-Arizona bill, which would allow employers to ask if their employees getting contraception are using it for “medical” or “sexual” reasons, and finally, as Mother Jones is reporting, House BIll 2036 which would be an anti-abortion bill to out-do everyone. Except, Mother Jones has a very important fact wrong (click here for the link to the Mother Jones Article).

The Mother Jones article claims the bill would impose the most restrictive gestational age limit, but Mother Jones is wrong because the proposed Arizona limit in the bill is 20 weeks, currently the gestational age limit in six states. (The current Arizona law allows abortion up to viability). Bill 2036 spells out how gestational age is calculated, from the last menstrual period, and that is apparently where Mother Jones got confused. See the excerpt below:

Not to go all middle-school health on you, but that’s not exactly the same as the actual date the egg and the sperm hooked up. Figuring out that exact point one became pregnant can be tricky. Most women ovulate about 14 or 15 days after their period starts, and women can usually get pregnant from sexual intercourse that occured [sic] anywhere between five days before ovulation and a day after it. Arizona’s law would start the clock at a woman’s last period—which means, in practice, that the law prohibits abortion later than 18 weeks after a woman actually becomes pregnant.

No, it doesn’t mean that the law prohibits abortion at 18 weeks. It means 20 weeks. Pregnancy has ALWAYS been calculated from the 1rst day of the last menstrual period. Always, always, always. When we do an ultrasound, we still use that convention. Perhaps it seems odd to non-obstetrical folks, however, since the last day of the period can be inaccurate (do you use flow? spotting? one spot of blood?), as can date of ejaculation (what if you have sex 3 days in a row?), and date of ovulation (how would you know that?), and the fact that fertilization takes 24-48 hours, the 1rst date of the last menstrual period is the only accurate date. Every other state law uses the last menstrual period (as does every obstetrical textbook) because that is the way we calculate gestational age.

There are many things wrong with the bill and to focus on an erroneous gestational age detracts from the real issues. The 20 week bills being introduced around the country are a response to the erroneous claims that a fetus feels pain at 20 weeks. Basing legislation on anything but facts is wrong.

In addition, 20 weeks is overly restrictive as many fetal anomalies are not diagnosed correctly until around the 20 week mark, leaving a mad scramble to get services in state or worse, have to pay to fly out of state. It happens more than you think.).

The bill also mandates an ultrasound, not a transvaginal probe (although mandating any ultrasound is wrong). It should be a medical decision. Mandating that a doctor ask if  the patient wants see the image is also in the bill, but I disagree with the reporter on why that is an issue. The bill only says the doctor has to offer, and studies tell us that the majority of women want to see the image when asked. My issue with that part of the bill is simply the intrusion of the state into the practice of medicine.

And finally, at the end of the bill this statement appears:

The legislature finds that abortion can cause serious both short-term and long-term physical and psychological complications for women…

Which is wrong. The complication rate with an abortion is lower than with a pregnancy that goes to term and there is no credible evidence based medicine that supports any psychological harm from a legal, safe abortion (worthy of a post in itself at a later date).

So there are many reason to take issue with House Bill 2036 from Arizona, but an 18 week gestational age limit is not one of them. Let’s make sure we focus on the facts.

Join the Conversation


  1. Thank you. Some of the gestational age stuff in that piece sounded wrong to me, but I’m no expert, so I appreciate an explanation from someone who knows what she’s talking about.

    I would really love to read an evidence-based post from you on the psychological issues surrounding abortion (or lack thereof). Last time I asked my resident medical expert to research it for me, the science was saying that women who choose to abort did not suffer mental health issues more than women who didn’t. I also understand that the number of women who regret their abortions is pretty small, contra all those anti billboards I see by the side of the highway. Unfortunately, I see this kind of “abortion is awful and painful but it should be legal” rhetoric from pro-choicers all the time. It would be nice to have the evidence available to link to.

  2. Thanks for tackling this issue and for the clarity of reason. The gestational age issue is so very important to understand. Years ago, a dear friend was subjected to the mad scramble you describe. It was just heart-wrenching for her, and the politically determined timeframe hanging over her head was an added burden during a time of grief and despair. The additional costs she incurred trying to jump through all those hoops became a terrible financial burden which required loans, payments and postponing another child while the bills were paid. A politically forced, artificial decision date magnified every aspect of her tragedy.

  3. I know that the convention is to date pregnancy from the last menstrual period, but in my experience doctors don’t tend to rely on women’s report of their LMP, but rather routinely perform early dating ultrasounds. Does it make sense to stick with this convention when there are more accurate ways of dating the pregnancy?

    1. Ultrasound incorporates the 2 weeks convention. So, when you have an ultrasound 4 weeks after you think you have conceived you will be 6 weeks pregnant. So wether you are calculating due date by the last menstrual period or by ultrasound it always uses the additional 2 weeks prior to conception. No doctor ever uses conception date and neither does any law. To imply otherwise is incorrect.

      1. Off topic, but does that mean most HCPs will not consider BBT charts? I am newly pregnant and know very well (by BBT, CM and one incident of unprotected sex) that I conceived around day 22. I don’t want to be pressured into a due date that is a full week earlier than it should be. Do I need to give an adjusted LMP?

      2. @KYLIE I am no ob/gyn but based on my experience, they do consider BBT charts but, just like the ultrasound scan, incorporates the 2 weeks convention. The day you ovulate/conceive would put you at 2 weeks pregnant.

        I have an odd menstrual cycle that spans anywhere between 35-42 days long. I thought I was infertile with a cycle like that, so a pregnancy did take me by surprise. Anyway, I only ovulated 3 weeks into my ‘pregnancy’. My ob/gyn uses the ‘corrected’ gestational age (#weeks from LMP – 1 week) when evaluating the little bean’s progress. She didn’t do so when I had my first ultrasound many weeks ago and, for a moment, scared the both of us into thinking that I had miscarried.

        Hope that helps, although I’d be interested to read a response from Dr. Gunter.

  4. This botched story has been perpetuated by Alternet, Tim Wise, RHReality Check and the ARHP. So frustrating, because our side prides itself on being more scientifically accurate.

  5. Dr. Jen…if you wonder how a woman would know when she ovulated…you need more education. Its actually not that hard to know when you ovulated…and in my own case, I can tell down to a 20 minute window when I ovulate because I feel intense cramping when I ovulate. Try reading “Taking Charge of Your Fertility” by Toni Weschler to learn more about how women can read their body signals to predict and detect ovulation.

    1. The ovaries do not have cortical representation, which makes is challenging to pinpoint the source of pain or cramping as ovarian pain. Much the same way as a heart attack is often felt as vague pain in the neck or the arm. So, the vague cramping that may or may not be experienced during ovulation could easily be dismissed as originating from another visceral source such as the bowel or the bladder. Furthermore, the nerves that innervate the ovaries cross the midline on their way up the dorsal column to the brain, which makes localization of the cramping to one side or the other difficult. Unless you are getting an ultrasound at the exact time you think you are ovulating it is possible, given the neuroanatomy of the ovaries, uterus, and bladder that you could be feeling something else.

      While some women can use cervical mucous changes to know if they are ovulating, this would not give you a 20 minute window. So, if you have your ovulation pinned down to a 20 minute window (and without and ultrasound at the exact moment to confirm that is what you are indeed feeling) then you are more viscerally aware than most.

      1. Thanks, Doc. I was going to ask you about “mittelschmerz” and here you are with the explanation I needed.

        Thanks also for pointing out the 18 v. 20 error, which I was all set to repeat in my blog. You’re right, these bills stink enough without us adding drama that isn’t there.

  6. Thanks for explaining this so clearly Dr. Jen. The link you provided to the Guttmacher Institute information is also really helpful to those who are trying to compare these nefarious laws across states.

  7. Having recently undergone an abortion (I live in the uk) I always find your blog to be insightful about how lucky I was to receive free, discreet and effective treatment. My councillor at the clinic told me that there was no proven link between women that have abortions and psychological or other mental health and well being issues, and that most women find that treatment leaves them feeling relieved and only guilt initially. Going from my LMP, the nurse found me to be 5 weeks, but after an ultrasound scan it was actually 6 weeks and five days (7 weeks by the time I had treatment), and it was the information from
    the scan which she put down on my chart. It seems a shame that there is such a battle with abortion laws in various states in the US, when it is so easy (and mostly free) to get treatment in Britain even if using a private clinic (charity run) like I did.

  8. Pingback: Georgia HB 954
  9. In addition to the misunderstanding regarding the gestational age convention, apparently nobody reporting on this understands much about reading legislation that’s amending existing laws; or either knows or cares how to compare the bill to the current law….the definition of “gestational age” in Arizona’s laws relating to abortion isn’t even new to the statute. I didn’t bother going back to see when it was originally drafted, but it’s in the current version. New or added language is in blue; language being removed is redlined; everything that’s in black is what ISN’T changing. Do people think the legislators are just playing with colored text to make their bills pretty?

    1. Oh, also I just linked to this post because you stated what I was trying to explain to people yesterday far more succinctly than I could! I was practically reduced to sputtering “It’s in EVERY book about pregnancy, EVERY website on fetal development, even the really shmoopy ones, if you LOOK at any statistical data on abortion regarding at what point in the pregnancy they’re performed it SAYS weeks of pregnancy dated from LMP….” Thank you!

  10. If you really are an OBGYN I’m shocked you’ve never heard of the existence of women with irregular periods or that you’d ever consider performing a procedure that’s dependent on an assessment of fetal age more accurate than ±two weeks without doing more than asking a patient about the date of her last period.

    Shame on you.

    1. Dear God, what is with you people?

      Ultrasounds are not required for pregnancy dating if the LMP agrees with the size of the uterus, however in the US is is almost always convention to get one.

      If the periods are irregular, then an ultrasound is obtained. Ultrasound, as I spelled out, uses the LMP convention so gives a date as if the periods were regular.

      Shame on you for being so rude. You could have asked if you needed clarification nicely. If you are nasty again I’ll flag you as spam.

      1. I’ve tried to stay as far away from this as I can. But I can’t. Sadly. I can’t.
        Correct me if I’m wrong, and I *could* be wrong, as I said, I’ve tried to stay away from this.

        But if the true goal was the medical necessity of the US .. then it would not matter if the woman was shown the ultra sound right?
        What is making the news here, the blips and blings that I’ve over heard as I’ve had my head buried in papers and textbooks and trying to avoid allowing my blood pressure to rise to rates that are sure to cause my head to explode into the stratosphere if I actually listened or read too much of it ..
        What is making the news here, the blips and blings that I’ve over heard as I’ve had my head buried in papers and textbooks and trying to avoid allowing my blood pressure to rise to rates that are sure to cause my head to explode into the stratesphere if I actually listened or read too much of it ..
        but what is being asked/required/requested .. trying to be made into law .. is that a woman not only must HAVE the ultra sound but VIEW the ultra sound ( be traumatized ..,er so that she can witness the life she is wanting to extinguish,,, yeah, that’s the right language right? etc etc etc).
        But if this was this was honestly a medical procedure .. then in fact, wouldn’t it be allowed for it to be done, screen away from the woman so that the technition or doctor saw what was needed? Isn’t this yet another scare tactic by those who want to oppress the oppressable with just one more weapon instead of looking for real ways these woman could find support and be supported, regardless of the decisions they choose?

        (Peggikaye from Twitter)

      2. Ultrasounds do not affect the decision to have an abortion. They should not be legislated. Whether it happens or now should be medical necessity. Like every other procedure and test in the US.

  11. This Colleague wrote “Basing legislation on anything but facts is wrong.”.
    I would ask my Colleague a few questions, based strictly on scientific facts:

    1) Did we not learn at Medical School that the life of the New individual begins at Fertilization?
    Is it not a biological fact (unanimously accepted by ALL scientists, including us MDs) that from implantation onwards the human embryo is an individual of the human species?

    2) Is it not a fact that the human embryo is NOT JUST A BLOOD of tissue developing into a Human, but rather a Human being undergoing development?

    3) When an abortion stops a Pregnancy…Is it not true that such action also KILLS an innocent individual?

    So…you see how wrong Abortion Laws are…because Legislation …”Basing legislation on anything but facts is wrong.”

    I am a Pediatrician with two PhDs in Developmental Biology…Please answer these basic questions based ON FACTS (not opinions)

      1. Dr. Gunter: What part of “answer these basic questions based ON FACTS” did you not understand? Namecalling is insipid and unprofessional.

      2. @Bonnie Reinders, i disagree. The guy is a troll. The random capitalization helps give it away, but the crux of it is his (or possibly her) use of extremely tired old cliché arguments which have been answered endlessly here and elsewhere, and demanding that Doc Gunter respond yet again, and that she accept his (or her) “facts” as if they were facts, such as defining the moment of implantation as the moment of individual personhood or citizenship or whatever else it is he (or she) is trying to establish in Q. #1.

        Gunter is being a professional. A professional doctor, and a professional web columnist, who has the right and duty to call trolls, trolls. Her time is precious and feeding trolls with detailed, factual answers only encourages them and exhausts everyone else.

  12. I’m cross-posting and editing slightly from other comments I made on another site.

    Many fertilized eggs (zygotes) don’t implant, and we don’t have funerals, issue birth and death certificates, etc. In fact, the first week or so after fertilization the cell divides 100s of times, and yet in 50-80% of cases it doesn’t implant. Yet they are living cells. Should a woman be keeping all of her sanitary napkins so they can be tested for the presence of fertilized eggs? What about those that need IVF – what do we do about those frozen embryos? Do we force a woman to have every one created to be used?

    Then the other issue is with “is all human life valuable?” Again, if a mother were in peril of dying because of the pregnancy, who do we choose? Should the mother be forced to die because of the embryo? So which life do we usually choose there?

    I do not like the thought of abortion, especially when I look at my own kids and what a beautiful thing it is to be a parent. But I also live in the real world and understand the world is not so black and white.

  13. Thanks, Dr Jenn for showing the evidence!

    Are our legislators trying to outdo the medical profession in coming up with a better way to determine an accurate age of the fetus than LMP so they can have fewer abortions taking 2 weeks off the fetal age? These legislators are the cause of driving up the costs of health care.

  14. Thanks for posting this and helping to explain the correct information about gestational age, so people can get past this silliness and start talking about the parts of the law that matter. Why aren’t more doctors stepping up to clarify this? Having so many pro-choice bloggers and journalists spouting off ridiculous accusations about Arizona re-defining pregnancy can only hurt the pro-choice movement. It makes it appear as though the Arizona law-makers have done their research, while the pro-choice opponents aren’t even willing to check wikipedia.

  15. Thank you SO much for writing this. I’ve been so frustrated – scouring everything i could trying to find justification behind the 18/20 week claim. Your article expresses EVERYTHING I have been feeling, and I’m so glad that you as a doctor have written something to clarify the hysteria. Thank you, thank you, THANK YOU!!

  16. THANK YOU so much for writing this! The misplaced outrage (from people on our side!) on this ‘redefinition’ has been driving me crazy! I’ve tried to explain to friends that this is nothing new, and your post is exactly what I was looking for.

  17. I favor restricting legislative voting (both federal and state) on matters involving female conception rights
    to soley female legislators. As a male, should I have an internal growth of any kind in my body, I would demand that the decision on what to do about it would be mine alone! We need more women in politics like Texas State Senator Wendy Davis who created an explosion of women in the gallery while filibustering one more attempt to strip every
    woman in Texas of the inherent right to control her own body.

  18. I myself experienced a miscarriage at around 10 weeks on 24th, November, 2012. This is despite an ultrasound test at 8 weeks that showed a normal and health fetus. I bled for around 2 weeks following the miscarriage. I received my normal menstrual period on 27th, December, 2012; approximately 20 days after I stopped bleeding due to miscarriage. I went for a pregnancy test after the period and it was negative. In January, we started trying for the first time to get pregnant and yes, after five weeks I tested positive. I could not be able to express my joy at getting pregnant again after a miscarriage that fast and easy.

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