Andrew Lansley and Nadine Dorries, perhaps unsurprisingly, don't read this blog...

During the second reading debate of the Human Fertilisation and Embryology bill, there was an interesting exchange between Andrew Lansley (the shadow health secretary) and Nadine Dorries MP, on the recent research into survival rates of extremely premature infants.

Lansley talks about the Trent study, that showed no increase in survival rates for infants born before 24 weeks:

The authors also report that no babies born at 22 weeks survived. Like other studies, they suggest that this might represent the limit of viability. I cannot say whether they are right, but I note that, of 150 babies born alive at 22 weeks over the whole period of the study in Trent, only 24 were admitted to intensive care. In the latest period, 2000-05, only nine were admitted to intensive care. From my point of view—I am not a scientist, but I can read statistics—in order to draw any conclusion from such a small number of cases, one would need to assess why those babies were being born so prematurely. Were they failing to thrive? Were they twins or other multiple births? Were they suffering from a genetic defect?

Abortions at 22 weeks would be of a foetus that was otherwise healthy, unless they were carried out on the specific ground of a prospective abnormality or handicap of the child concerned. So while such a baby would require intensive care, and doubtless very large numbers might not survive, I do not regard that study as providing conclusive evidence that a baby cannot be sustained at 22 weeks.

I would personally be loth to move from the principle of linking the time limit for abortion to the viability of the foetus. That is where it was established in 1967; it has moved over time. It is arguable, but I would argue personally that the evidence would support a further reduction—in my view, to 22 weeks—in order to ensure a prospective legal framework that could accommodate improving medical science.

To which Dorries has this to say:

I am sure that my hon. Friend is aware of other studies—for example, in University College hospital, London, and in other countries—showing that if poorly babies who are born prematurely receive immediate good neonatal care from a specialist dedicated team of staff, the outcomes are very much better. University College hospital figures are much better than those emerging from the Trent study. One conclusion from the Trent study is that anyone going into premature labour should go to University College hospital and not to the Trent region.

This is exactly what you can't conclude from a comparison of the Trent and University College studies. It's difficult to compare the studies, because the Trent study includes all infants 'alive at the onset of labour', while the UCLH study included only infants that were born alive. Another issue with the UCLH study is that the numbers of infants admitted to the neonatal intensive care unit varies wildly between the different time periods of the study. This may be because the number of subjects is so small, leading to a large amount of statistical noise. Or it may be because those time periods are not directly comparable, perhaps due to differing policies on which infants should go to the neonatal intensive care unit through time.

And Lansley replies:

My hon. Friend may have gathered from what I said that I am effectively arguing that in circumstances where neonatal intensive care was provided to all such babies born at 22 weeks and where the foetus was otherwise healthy—or rather the baby was healthy at that stage—the prospects for survival at 22 weeks may well be far greater than suggested by the negative view expressed in the study from Nottingham and Leicester. It is not for me to say any more than that, but I think that it provides a basis for reducing the limit—albeit, in my view, by just two weeks.

In fact, the Trent study (Nottingham and Leicester) is more likely to give an accurate idea of the prospects for survival, because it is a multi-centre study (including 16 hospitals in the Trent health region) while the University College study concentrates on a single hospital. So the Trent study is less likely to be confounded by selection bias, and includes a much larger number of subjects, leading to statistically more robust results. It's difficult to see how Lansley can come to the conclusion that the study 'provides a basis for reducing the limit', given that it shows there has been no change in survival rates before 24 weeks since the early 1990s. Happily, the lead author of the Trent study, Prof. David Field of Leicester University, has pointed this out.

There may be other reasons for seeking a reduction in the limit for abortions, but the Trent study is not one of them. To suggest otherwise is simply to misrepresent the research.

Nadine Dorries makes an attempt to look at the evidence. She fails. [updated]

Nadine Dorries seems to have realised that simply dismissing as 'desperate tosh' a study in the British Medical Journal won't cut the mustard. The study looked at survival rates of premature babies in the Trent region of the UK, concluding that survival rates for births before 24 weeks had not increased since 1994-9. This undermines the argument that those survival rates are increasing, and the time limit for abortion should be brought down to 20 weeks from the current 24 weeks. Dorries has now at least attempted to address the evidence, on the 20 weeks campaign website. This is a marked improvement, but I think her effort still falls somewhat short.

First, some nonsense. Dorries writes:

"We were somewhat surprised to see that the article was not in this week's paper edition of the BMJ which many doctors did not receive until Saturday. Why then rush to get it onto the web and into the public domain? The BMJ editorial said that upper time limits were to be debated in the House of Commons 'this year'. What it didn't say is that they are actually to be debated and voted on in just ten days, on 20 May. So the rush to get this into the public domain was to influence that debate".

If you can't use the latest research to 'influence debate', then what is it for? Apart from that, it is perfectly normal for research articles to appear on journal websites some time before they appear in print. That is precisely so that articles can reach the public domain once they are ready for publication, without having to wait on production schedules.

What of the science, indeed. Dorries says that "the Trent study looks at results from 16 hospitals and has been running for years. It is not new and other studies have been published based on more recent data". She also claims that the results from Trent "have always been poor and well below those seen in top neonatal centres worldwide". As evidence for this, she cites a study from the University College London Hospital (UCLH). This study is a single centre cohort study comparing survival rates in the years 1981-85, 1986-90, 1991-95, and 1996-2000. [The first thing to note here is that the Trent study uses data up to 2005. So it is actually using much more recent data than the UCLH study.] The UCLH study found that "There was a progressive increase in survival at all gestational ages over the 20-year period".

This seems to be a classic case of how you have to be careful with research. The first thing to note is that the number of babies in the UCLH study is small. The total number of babies in the study was 12 for those born at 22 weeks gestation, and 56 for those born at 23 weeks gestation, over 20 years. This compares with 261 born at 22 weeks and 370 at 23 weeks, over 10 years, for the Trent study. The Trent study is likely to give more robust numbers. Dorries, on the other hand, writes that the UCLH study "showed no survivors at 22 or 23 weeks in 1981-85 but 71% (5/7) and 47% (8/17) respectively in 1996-2000". Note the tiny sample size this statement is based on. In the UCLH study, the authors don't give percentage survival rates for births at 22 weeks, because the sample sizes are simply too small to draw any conclusions. There is something odd about the admission figures here too. For births at 22 weeks gestation, there was 1 admission in 1981-85, 3 in 1986-90, 1 in 1991-95, and 7 in 1996-2000. The comparable figures for births at 23 weeks are 7, 23, 9 and 17. There are very large variations here that suggest that the different time periods may not be directly comparable.

Perhaps the most serious problem with comparing the Trent and UCLH studies, though, is that they don't appear to be measuring the same things. In the Trent study, the authors write "We included in the study infants alive at the onset of labour". In contrast, the UCLH authors write "All infants born between 22 and 25⁺⁶ weeks of gestation between 1981 and 2000, who were admitted to the tertiary neonatal intensive care unit of UCLH (UK), within 1 week of birth, were enrolled into our study. In addition, the UCLH labour records for the years 1991–2000 were scrutinised to identify all infants who were born alive between 22 and 25⁺⁶ weeks of gestation, but who died in the delivery room". Hence the Trent study includes still-births as deaths, but the UCLH study does not. According to the Trent study, of births at 22 weeks, 43% were stillborn in 1994-99, and 40% in 2000-5. Of births at 23 weeks, 28% were stillborn in 1994-99, and 20% in 2000-5. For the UCLH study we don't know what these rates are. The Ministry of Truth blog has noted an anomaly in that the UCLH study reports a massively lower proportion of deaths in the delivery room compared to the Trent study. So there is at least a possibility that the UCLH survival rates are inflated in comparison to the Trent study by selection bias: perhaps more infants are being admitted to neonatal intensive care in Trent than in UCLH.

It's also worth noting that the Trent study covered a whole area (the Trent health region in the UK), while the UCLH study covered a single hospital. As the authors of the UCLH study write, "Large population-based studies [such as the Trent study] have the advantage of avoiding problems of selection bias and enable the accumulation of large numbers to reduce statistical errors. However, they inevitably represent the outcome from a very heterogeneous range of perinatal facilities...It is therefore inevitable that these units encompassed a wide range of staffing, resources and expertise in the care of extremely preterm infants. In addition, it seems likely that the maternity units encompassed a range of management policies (both obstetric and paediatric) towards infants born at the limits of viability, ranging from ‘proactive’ to ‘noninterventionist’. Hence, it is not surprising that average survival figures obtained from large population based studies will be different from those observed from single centre cohorts". As the editorial in the BMJ that accompanies the Trent studies says, "Single centre studies are confounded by selection bias and tend to overestimate the likelihood of survival". In other words, to compare the Trent and UCLH studies in the way Dorries is trying to do, and draw the conclusion that survival rates in the Trent health region are 'poor', is not a sensible thing to do.

So Dorries has looked at the evidence, which is better than dismissing it as 'tosh'. However, she seems to be drawing erroneous conclusions from an inappropriate comparison of two different studies. By coincidence, this inappropriate comparison supports Dorrie's agenda. How convenient.

Yes, but what about the evidence? Nadine Dorries and the BMJ

This morning my Grauniad was carrying a story about new research, published in the BMJ, that suggests survival rates for premature babies born before 24 weeks are very low and have not improved, despite advances in medical care.

Now, I haven't actually read the whole study, but I've glanced at the abstract. It's a cohort study that looks at births of babies between 20 and 26 weeks in the Trent health region in the UK over two time periods: 1994-9 and 2000-5. The study found that although there was a significant increase in the number of surviving babies in 2000-5, this was attributable to an increase in survival rates for babies born at 24 and 25 weeks. There was no significant increase in survival rates for babies born before 24 weeks.

This is an important finding because the House of Commons will soon debate whether to lower the lower the legal cut-off point for most abortions from 24 weeks to 20 weeks. One of the arguments has been that advances in medical science mean that more and more babies born before 24 weeks are surviving. The research shows that this appears not to be the case.

What to do if you're on the side of the debate that wants a reduction to 20 weeks? If you're Nadine Dorries MP, you go in for some textbook fallacious reasoning, relying in particular on ad hominem and argument from incredulity.

No improvement in neo-natal care in twelve years? Really? So where has all the money that has been pumped into neo-natal services gone then? A baby born at 23 weeks today stands no better a chance of living than it did in 1996? This report is the most desperate piece of tosh produced by the pro-choice lobby and it smells of one thing, desperation.

Well, the evidence seems to suggest that a baby born at 23 weeks today really does stand no better chance of living than it did in 1996. It's no good just saying you don't believe it; you need to explain why that interpretation of the evidence is incorrect. Dorries also describes the British Medical Journal as the "trade magazine" of the British Medical Association. Because the BMA funds a pro-choice group, research published in the BMJ can be dismissed as emanating from the "pro-abortion lobby". In fact, the BMJ is a peer-reviewed medical journal, publishing "original scientific studies, review and educational articles, and papers commenting on the clinical, scientific, social, political, and economic factors affecting health." It is something more than a trade magazine, and for Dorries to describe it as such is disingenuous to say the least.

As I say, I have not read the whole paper. For all I know, there may be some problems with it. But Dorries is simply not contributing to a useful debate by dismissing the study out of hand. The paper gives us the evidence, and it is up to us, as a society, to decide what to do about it. We can't do that by falling back on fallacious reasoning that supports our pre-conceptions.

Update: Dorries continues to mis-represent the BMJ paper, writing that "For the BMA to argue that the survival rates of neo nates born 12 years ago should endorse the 24 week limit today, is, as I said yesterday, an act of desperation, but one that suits me and the media opportunities such a biased piece of 'research' provides." First of all, it is not the BMA that is doing the arguing. The research was conducted by a team working in the Department of Health Sciences at the University of Leicester. Second, the paper compares data from 1994-9 to data from 2000-5. Where Dorries gets '12 years ago' from is anyone's guess. Again, it is no good simply stating that the work is 'biased'. You need to explain why it is biased. I'm fairly sure that Dorries can't do this.