As I was driving home from work on New Year's Eve in 2007 I smoked my last cigarette; I remember it well. The smell and taste of those last few drags can still easily be recalled from my memory. My decision to quit was fuelled by my concern that an increasing proportion of my pay check was flowing into the pockets of the tobacco giants and, of course, the fear of cancer. What never crossed my young mind, even as the last stump burned to the end, was the possibility that my favourite bad habit was damaging my fertility. I am not saying that my choice to spend my youth puffing away has left me infertile, I don't know whether anyone could tell me if that is true. However, a review of recent scientific literature performed in 2008, and another published in 2011, both concluded that cigarette smoking compromises every aspect of the reproductive system. Whilst the results are clearly not wonderful news for a smoking lady hoping to make a baby au naturel, they don't really tell you whether smoking will ruin your eye-wateringly expensive and hope-laden IVF cycle.
Yes, you guessed it, we are here again, taking another step forward in the research journey that is Operation Big Belly. And, as you may already know, we have so far investigated the possibility that food, alcohol and caffeine could reduce your chances of an IVF baby. Now that we are getting started I should remind you that the ground rules can be found here.
So, even though the clues seem to be screaming at us "Of course smoking is bloody terrible, you fools", let's ask the question anyway, we might be pleasantly surprised: will smoking screw up your chances of a successful IVF cycle? One health authority in Scotland is so sure that cigarettes are completely atrocious that it has banned couples who smoke from having IVF treatment on the NHS (see here). Now, what the Scottish choose to do might be extremely fascinating (if I were cynical I would say their decision was swayed a teeny weeny bit by the desire to spend less of their health budget on the not-so-election-busting infertile couples), but what can science tell us about smoking and IVF?
This time at least there is a respectable body of data to get yourself excited about. As far back in time as 1996, there was a healthy level of research interest in IVF and smoking. The first review of published studies that investigated the role of smoking in IVF success, found seven papers worth examining and revealed that, although there was variability between the studies, the conception rate was lower and the miscarriage rate higher in women who smoked.
A year later, a research group from Austria published the results of a meta-analysis that investigated the effects of smoking on IVF results. The data review comprised of eight studies, including the authors own, and analysed the outcomes of 2314 IVF treatments. The studies reviewed yielded conflicting results and with some indicating that smoking didn't impact the IVF success rate. However, when all the data were taken together, the meta-analysis revealed that non-smokers were significantly more likely to get pregnant during their first cycle than smokers, and that smokers require twice as many attempts to achieve pregnancy.
If you step forward just a few years more, this time to 2005, you will reach a pretty thorough review conducted by Hilary Klonoff-Cohen (we met her before here). This lovely lady has gone to the trouble of reviewing 22 articles, including the studies mentioned above, and the data, as with the previous reviews, was somewhat conflicting. She did not conduct a meta-analysis, so it is not possible to say if the studies which demonstrated no effect on IVF success rates for smokers would have remained significant when the body of evidence was examined as a whole. However, she did conclude that "despite the variations between the studies, there was compelling evidence that smoking had a negative influence on IVF outcome".
If you manage to pick yourself up from those revelations and roll forward a few years, you will find that you have landed at the feet of a second meta-analysis conducted in 2009. On this occasion, a collaboration from the UK (yay!) analysed data from 21 studies to investigate the impact of smoking on IVF outcomes. The investigators found that smokers had a lower chance of pregnancy, a higher risk of miscarriage and ectopic pregnancy, and a lower live birth rate. Non-smokers were found to be twice as likely to get pregnant and have a baby at the end of it all. Not only that but the analysis went deeper, smoking was shown to be bad for every step of the IVF process; smokers required greater stimulation, had fewer eggs, lower fertilisation rates, and a higher chance of implantation failure. The authors concluded their paper by stating "There is particularly overwhelming evidence for a decreased clinical pregnancy rate amongst smokers, in addition to the strong implication of a negative effect on live birth rate, miscarriage rate, ectopic pregnancy rate and fertilisation rate". Phew! They weren't messing about, were they?
I could find no more reviews or meta-analysis studies since the one performed in 2009, described above. However, there have been more experimental studies that have investigated the relationship between smoking and IVF success. Since 2005, I realise I have gone a little further back than the last meta-analysis, researches have discovered that smoking is associated with lower delivery rates and higher miscarriage rates, decreased uterine receptivity and increased numbers of multiples, a lower number of fertilised eggs and correspondingly lower pregnancy rates, reduced ovarian reserve and, once again, correspondingly lower pregnancy rates, poorer ovarian responses to stimulation and impaired embryo development.
Well, if that wasn't quite enough to put you off your cigarettes for good then maybe the final study will convince you. In 2011, a research group based in Israel discovered that, when women smoked, even if the doctor put great quality embryos back into the uterus, the pregnancy rate was lower for smokers than non-smokers. Oh dear, even an excellent embryo can't help you!
In the interest of fairness, I should point out that, since 2005, there had been one, yup just one, study that found no difference between smoking and non-smoking groups of women undergoing IVF treatment.
So there you have it. If you are planning to do IVF and you enjoy a smoke, you might want to think about enjoying it a little less often or, preferably, not indulging at all.
Writing this post has made me a little sad; I wish I could go back and plead with my younger self not to pick up that first cigarette. And, yes, there was an adolescent boy, who I was attempting to impress, connected to the decision to take my first puff. But I doubt that young lady would have listened to a word of it. Babies seemed so far away and she comes from one of the most fertile families on the planet: three brothers, three sisters and thirteen nieces and nephews. I know you shouldn't regret the past, and on many occasions smoking gave me real joy, but, as the great Cher once said, if I could turn back time.......