Newsflash! Gans and Leigh: Still no evidence that women are harming their babies for cash.

Back in November 2007, tigtog and I discussed at length the paper on the baby bonus introduction by Andrew Leigh and Joshua Gans, “Born (Again) on the First of July: Another Experiment in Birth Timing”[1]. The paper has now been revised for international publication, this time with mortality data.

Their thesis back in 2007 was there was an introduction effect “delaying” births around the time of the baby bonus introduction, and their data does show a clear change in pattern.


The introduction effect has the potential to create potential issues with hospital resource management, an issue Gans and Leigh should have stuck to. However, they boldly branched out into saying that the “delays” were leading to “high birthweight” babies, and that this could only lead to adverse health outcomes. No alternative hypothesis was considered, and their assumptions weren’t elucidated or examined.

Gans and Leigh hypothesisedbaldly stated in their 2007 paper:

Although our study cannot speak directly to the health effects of delaying births, it seems likely that decisions to delay births for non-medical reasons can only have adverse health consequences for babies and parents. While babies born pre-term and/or underweight are less likely to be healthy, the same is also true of babies born too late and/or overweight.

Health consequences for “parents”? For a start, what are the likely health implications for fathers and non-bio parents? OK, so they’re using “parents” as a proxy for “mothers”. Where do they present data on consequences for mothers? Nowhere. The hands are flapping as fast as they can.

On to the babies. The more sensible and obstetrically-experienced among us rapidly realised that what was more likely to be happening was that “routine” inductions and C sections, typically done around 38-39 weeks, were probably being rescheduled to a time closer to when the birthdate would have naturally lain had the interventions not been performed.

Most of these procedures are done for no urgent medical reason (the weekend effects shows that very clearly) – twins or breech presentation, “social” reasons, repeat C sections, presumed or fabricated macrosomia, and so on. For most of these situations, not only is there no medical reason to intervene so very early and/or no compelling medical reason to do a C section at all. In fact, in the absence of very urgent indications like impending eclampsia, there is often no reason to interfere to change the birthdate at all. Oh, apart from so that obstetricians can start their inductions first thing, run a money-spinning C section list in the morning, then catch or excise the induced babies in the afternoon, instead of attending births when they happen spontaneously and inconveniently.

I think the concocted obstetric workforce shortage could be playing a role here. Perhaps if there were wider recognition of the fact that obstetricians don’t need to be involved at all in most births, obstetricians would be less likely to get away with their “Oh, if we don’t schedule it now, I might not be available at all, because I’m so terribly busy” act?

On the birthweight issue: if you start holding off a little on unnecessarily early deliveries, it follows that the overall average birthweight will rise slightly, and more babies will slip into the >4000 g range (>8.8 pounds). That weight range is now considered a disaster waiting to happen by those who like to panic and slice, but many many completely normal health full-term babies fall into it, and most of them can be birthed normally without complications. In fact, one study found that the biggest determinant of birth outcome was not whether the infant was actually high birthweight, but whether the obstetrician predicted it was going to be. More on why projected “fetal macrosomia” is an overplayed hand in the birth-intervention game is here.

There ensued cross-blog discussions (at Hoyden (and here), at Leigh’s place, and at Gans’s place) on the underlying mechanisms and likely health implications, in which Leigh steadfastedly refused to examine his faulty assumptions – the assumptions that obstetric interventions were only done for pressing and clear medical reasons, and that any “delays” in the current pattern of births and deliveries was likely to lead to “overweight” babies and adverse health consequences. The press latched on to the idea of unhealthily fat babies – there’s a current moral panic buzzword for you! – and ran with it, repeatedly. (The Age, the West,, ABC, ABC)

Now there is what looks to be a revised and expanded version of the First of July paper available [via the Social Science Statistics Blog at Harvard]:

“Born on the First of July: An (Un)natural Experiment in Birth Timing” [2]

This newest paper doesn’t seem to be obviously dated at that link, but from what I can deduce, it is the version in press at the Journal of Public Economics. [Note that it is not the original version of the Leigh and Gans July 2006 first-draft discussion paper [3], though they have the same title.]

In the 2007 version that we were debating, the hand-waving section on birthweight contained only one piece of medical background, a bit of fairly tangential Swedish medical data, a study finding a correlation – NOT a causative relationship – between very high birthweight and low Apgar scores, and post-term and low Apgars. [Apgar scores are a crude measure of neonatal well-being shortly after birth, and correlate somewhat with outcomes.] It contained no mortality or morbidity data from Australia, and more importantly, no other medical data, and no consideration of the background or implications of the one piece of data they did include.

Note that in the Swedish study, the Apgar slump with post-term birth did not occur until 42 weeks and after. When interventions for non-urgent reasons are typically scheduled at a presumed 38-39 weeks, the births can be as early as 37 weeks (or even earlier), as medical dating cannot be more accurate than that – and births at 38 weeks and before are also associated with a sharp rise in infant mortality in the Swedish data and elsewhere. The optimal birth timing in the Swedish data was at 39, 40, and 41 weeks. When routine C sections and inductions are held off for a week or even two, they are very unlikely to be “delayed” beyond 41 weeks, so the babies born with “shifted” birthdates around the baby bonus time were, in fact, very likely to have been born in the safest timing zone, as far as the Swedish study is concerned – very possibly even more likely than at other times.

On to the current paper and the punchline, if you’ve lasted with me this far. Gans and Leigh have confirmed that the shift in birthdates was driven by changes in induced and scheduled C section births:

“The largest drop in births in June occurred in vaginal induced births, and the largest rise in July occurred in Caesarean sections.”


They now have perinatal mortality data for the periods immediately before and after the baby bonus cut-off, the period during which births were so “dangerously delayed”. The result? Despite there being a 3% increase (*gasp!*) in “high birth weight” neonates, mortality was unchanged. This is a giant fizzog.

So women weren’t rampantly and recklessly harming their babies for money after all?

No-one appears surprised.


[1] Joshua S. Gans and Andrew Leigh. 2007. “Born (Again) on the First of July: Another Experiment in Birth Timing” The Selected Works of Joshua S Gans
Available at:

[2] Joshua S. Gans and Andrew Leigh, “Born on the First of July: An (Un)natural Experiment in Birth Timing*”
In press, Journal of Public Economics

[3] Gans, J.S. and A. Leigh (2006a), “Born on the First of July: An (Un)natural Experiment in 
Birth Timing,” ANU-CEPR Discussion Paper, No.529, Canberra. ” Available from

Categories: economics, gender & feminism

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21 replies

  1. I’m so glad you picked up on the follow up, Lauredhel; the initial back-and-forth where Leigh (?) tried to argue based on one study where breech births demonstrated a better outcome for caesarian sections has been annoying me for months. It’s good to have closure.

  2. L – thanks for this post.
    The conclusions from Gans and Leigh on the copy I have says:

    There are two important implications of the analysis here. First, these results suggest that when policymakers are announcing a new policy, they should think not only about the behavioral distortions of the policy over the long-run, but also of the possibility that the introduction of the policy may itself cause distortions in the short-run. Such effects are likely to be largest when a sharp policy discontinuity is announced in advance.
    The event studied here provides a clean example of the potential magnitudes involved.
    Second, we have identified a very significant disruption to normal operating procedures for maternity hospitals and staff in Australia. This disruption appeared to impact both planned and unplanned birth procedures. Although we do not find evidence of a rise in infant mortality, the overall health effects of this are not known. However, with more data, this event provides an opportunity for health researchers and economists to study the impact of a large disruption in a well-developed, modern medical system.

    I don’t have many problems from these conclusions although the media, and some of the authors, responses to earlier drafts especially on the issue of health outcomes were problematic.
    I’m not sure why it is gobsmacking for some people, especuially governments, to learn that financial, or other, incentives /disincentives can influence behaviour. Or that patients and medicos are influenced by these incentives – the weekend effect as noted by the authors, is only but one example.

  3. FXH: I’ve said it before, and I’ve said it in this post, but I’ll say it again: I have no problem with these economists examining the (potential/actual) influence of the introduction effect on hospital staffing and resource management.
    What I have a problem with is their comment that the brief holding off of some scheduled deliveries “can only have adverse health consequences for babies and parents”, the uninformed and frankly ridiculous attempt at the medical analysis (and defence of same), and Leigh’s steadfast refusal to engage with substantive critique from people who know far more about the issue than he does.
    It’s been nearly a year and still the medical section in the revised paper doesn’t take into account the critique and the large number of references we have offered them. All it does is add the mortality data, and wistfully hope that more data might prove them to be right after all.
    Leigh also steadfastedly refused to revise his bald statements and mark them as tentative hypotheses: he wanted to present his flawed “common sense” assumptions as fact.
    I think having economists with this attitude in positions of power is a dangerous thing. Admitting what you don’t know is a crucial skill.

  4. Just think…babies being born when they themselves decide they’re ready isn’t harmful. And that mothers might have the best interests of their babies at heart. All so radical!

  5. L – I wasn’t directing the comment at you. I only talking about the conclusion above.
    I have now read their “medical” section and I think it was foolish of them to venture into the territory unless they had at least some crude data suggesting worse outcomes. Still economists seem to have no fear about making pronouncements in areas where they are not experienced and haven’t even got a real idea of the current debates and state of play.
    Given the time and effort it takes to complete a Cochrane review on a small relatively contained area I’m not sure why they even tried to look at mortality outcomes.

  6. Still economists seem to have no fear about making pronouncements in areas where they are not experienced and haven’t even got a real idea of the current debates and state of play.

    Totally this. Nodnodnod.

    Given the time and effort it takes to complete a Cochrane review on a small relatively contained area I’m not sure why they even tried to look at mortality outcomes.

    I think it is quite reasonable to gather mortality data around events like this, so long as the gatherers are doing so with an open mind and with full awareness of the limitations of the data – and, as you say, with a background in research in the field, or perhaps as a collaboration. If there had been a real spike _or dip_ around that time, it would not be conclusive, but it might be a useful area to highlight for further investigation.
    I’d be interested to know whether there were any discernable changes in short-term NICU admissions around the introduction effect. Near-term babies (born very slightly too early), for example, often have brief admissions to NICU, and this would be likely to be a much more sensitive measure of health effects.
    But overall, and I think I need to take a few steps back here – the root of the problem that I see is the pervasive and fixed misapprehension (and Gans and Leigh aren’t anywhere near alone here!) that all obstetric intervention must be good obstetric intervention. They weren’t looking for any changes in mortality, they were looking for an increase. This attitude carries a risk of cherry-picking and distortion of the data.

  7. Thank you for this. And I’m with you, Sister Suffragette. Heaven forbid that babies be born when the body decides they’re ready. Nope!
    Father Doctor knows best!

  8. So I am a little confused, Lauredhel. You are criticising us now for doing what academics do all of the time and revising their paper to qualify statements and eliminate things that were written that were confusing and could easily be taken out of context?
    That said, our position, as it has always been, is that we can’t tell whether there were adverse consequences or not from successive governments reckless behaviour on toying with health practices. We err on the side of not putting poor incentives in place. But you have a right to agree with them that they face no risks in doing that. But recognise this: you have no systematic evidence of that either.

  9. Joshua,
    I’m an academic. What I do, is revise my work, have other peple read it, or even submit it for peer review, before I put it out in the world.
    It makes for fewer publications but also fewer horrifying cringes at seeing my mistakes take on a life of their own.

  10. And so do I. Guess what, different academics have different opinions about what might cause issues.

  11. Joshua:

    ”That said, our position, as it has always been, is that we can’t tell whether there were adverse consequences or not from successive governments reckless behaviour on toying with health practices.”

    I’m having trouble reconciling this with this:

    ”it seems likely that decisions to delay births for non-medical reasons can only have adverse health consequences for babies and parents”.

    There is no “out of context” here; I’m not confused. Your statement was very clear. Please stop trying to characterise informed critique of the history of this part of the paper and Leigh’s defences of it as “confusion” – it does not flatter you.
    I have not, in fact, criticised your team for revising the paper. I am glad that finally you seem to have realised that adverse health effects are not the only possible outcome of the introduction effect. A deeper, more informed analysis of the interplay birthweight and birth outcomes would be nice, in place of the current superficial and misleading remarks in the paper (but that would take a lot of medical research from your team, and I realise that it is obviously not your field.) A recognition from Leigh that his dismissive handwaving was borne purely of misinformation and stubborn embarrassment would be nice, but I’m not holding my breath on that. Perhaps a formal withdrawal of the previous paper, or a published erratum, may be useful.
    Question: Was the hypothesis that holding off on birth interventions may have health _benefits_ ever seriously considered by your team? Why or why not?
    Since we’re talking about evidence base, you have presented no evidence that the government’s action can be accurately characterised as “recklessly toying with health practices”. So far, all you’ve done is show the introduction effect to be medically benign. A few women whose birth interventions were not urgent had them a few days later than they might otherwise have had them – what exactly is “reckless” about that?

  12. And so do I. Guess what, different academics have different opinions about what might cause issues.

    Here’s the thing, Joshua: If you did consult an “obstetric expert”, you only consulted someone who is part of the problem. I’m coming at this not from the point of view of backing a Health Minister or an economist, I’m coming at it from a woman-centric point of view, a feminist point of view.
    You seem to think that I care who’s going to win in your economist-health minister pissing competition. I don’t, except inasmuch as it might impact on women. You’re all part of the SAME problem, the same patriarchal system in which a bunch of people in power argue over women’s bodies while all the while completely failing to include or listen to those women.
    Any possible carelessness you might perceive in this issue pales into complete insignificance at the recklessness with which women are treated within the obstetric-industrial complex every single day of the year.
    If you’ve read any of my previous posts on birthing, you’d understand where I’m coming from on this. If you haven’t, you’re likely to stay in contention for this week’s Missing The Point award.

  13. Joshua, I’m just reading this Slate article you referred me to – apparently as some sort of support for your baby bonus paper?
    This is about an incentive programme for Russian women to give birth on a single particular public holiday, an incentive announced 39 weeks before that day was to fall. I’m a bit lost on its relevance to the Australian baby bonus introduction effect.

  14. Well all we have done throughout 7 papers now is raise concerns that decisions on planned birth timing are being driven by non-health outcomes. Near as I can tell that is a line you have been pushing but, for reasons that remain inexplicable to me, you seem intent on placing us on the opposing side of that debate. (I am pretty sure that you don’t think having fewer babies on April 1 or weekends or when the Annual Obstetrics conference is on is a sign of a well-functioning system). So give that a Missing the Point award or whatever. It’s your blog.
    The Government rejected our call for an inquiry into this stuff and the Professional Associations have been dismissive. So our views and analysis will remain in the papers. Attack them or use them as you see fit.
    Also, please don’t go calling out Andrew to respond. He is working for the government and can’t talk publicly about anything (as his blog has clearly stated for sometime). So such calls are unfair.

  15. Joshua, what about the possibility that we so totally accept the idea that non-health outcomes/incentives are motivating many health decisions, including planned birth interventions, that this idea is simply not the focus of our disagreement?
    What interests me in the data is that in the case of birth incentives, it’s quite possible that a financial incentive for the patient to delay birth interventions is acting against the trivially obvious pre-existing financial incentives for the obstetrics industry to advance birth interventions, and that incentives that delay birth interventions may actually be a good thing for those infants whose births are now delayed to closer to the natural due date (no matter how much such blips disrupt hospital administrative aspects).
    I would really like to see the data used to perhaps prod some adequate investigation into obstetrical overservicing, but as long as your papers only mention possible negative consequences of delaying birth interventions that simply won’t happen.

  16. As first hand experience is an experience like no other, I am intimately aware of the predatory and rapine obstetric practices currently employed by the hospital system in Australia. Practice and consent guidelines are openly, knowingly breached. One less baby in ICU, and one less woman used and discarded due to these delays, was an unintended added value, a bonus to the bonus. Any study that brings out, even as a sideline discussion, the real issue, that of knowingly harmful and unnecessary actions committed against pregnant women, unborn babies, and nervous, overawed partners, is welcome.

  17. Wow Lauredhel. Thanks. Just… thanks. What a post. *lost for words for once*

  18. Why thankyou, Emma.
    PS… little gnomes have been nominating your posts for the Carnival. If you haven’t done so before yourself, are you planning to submit next month? Spread the word!

  19. Hi Lauredhel, one of those little nominating gnomes was me! but not all of them 🙂 I’m thrilled that Blue Milk included the Orgasmic Birth plug, spreading the word about it has been hampered by our inability to use the public media because it is not classified.
    Your post above inspired me to start getting a media pack together regardless. You seem to know a great deal about unnecessary birth intervention in Australia. Do you have any knowledge specific to Victoria? I only have anecdotes, morbidity reports and a dated study to go on and it all seems fairly unconvincing at the moment :-


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