The Vices: Caffeine, Alcohol and Tobacco - Expecting Better: Why the Conventional Pregnancy Wisdom is Wrong and What You Really Need to Know by Emily Oster
La donna in gravidanza che vuole informarsi sui rischi che corre è, all'apparenza, sommersa di info a portata di click...
... Finding information on the Internet about caffeine, alcohol and tobacco during pregnancy is easy. There are official recommendations from national organisations, there are recommendations from specific doctors and books and there are other people, on chat boards and blogs. There is no shortage of opinions, but there is a definite shortage of agreements...
Ma s'imbatte in info contraddittorie, anche quando si affida all'ufficialità...
... The fact that people on chat boards argue is a given (what else are these boards for?). What I found more surprising was that official recommendations disagreed with one another...
Alcol: c'è chi raccomanda l'astinenza e chi la moderazione...
... In the case of alcohol, although all the pregnancy organisations in the United States recommend a policy of abstinence, similar organisations in some other countries indicate that occasional drinking is fine...
L'esempio inglese...
... In the UK, the National Institute for Health and Clinical Excellence (NICE) advises healthcare professionals to tell their patients to avoid drinking in the first three months and if they do choose to drink, they should drink no more than one or two UK units of alcohol once or twice a week...
E con il caffè andiamo ancora peggio, la confusione è massima...
... Caffeine is similar – recommendations differ across countries, yes, but also across books and across obstetricians and GPs within the same country. My obstetrician said having less than 200 milligrams a day (about 475 millilitres of coffee) was fine. My sister-in-law’s obstetrician told her no more than 300 milligrams. My best friend’s said no caffeine. When we turn to books, the aptly named The Panic-Free Pregnancy takes the stance that caffeine in moderation (up to 300 milligrams) is fine. The Mayo Clinic Guide to a Healthy Pregnancy rules out caffeine in any dose... What to Expect When You’re Expecting goes with the 200-milligram rule but indicates that you should check with your obstetrician...
Se poi vuoi conoscere le evidenze su cui si basano i consigli dati, l'impresa si fa ardua e le info si diradano improvvisamente...
... I still would have wanted to know what evidence backed it up. But my desire for evidence was made even more extreme by the fact that people disagreed...
Perché tanta diversità? Sono i dati a differire o le interpretazioni?
Chi va a fondo scopre che anche la qualità delle ricerche disponibili varia...
... When I got into that, I saw why these recommendations differed so much and were so confusing: the quality of the medical research on this varies enormously...
La metodologia ottimale delle ricerche è il random trial. Di cosa parliamo?...
... At the end of the day we wanted to be able to say something like: “If we gave more people televisions, attitudes towards women would improve.” One great way to do this would be to randomly pick some people to get televisions. You could watch them over time and see if their attitudes changed more than the people to whom you didn’t give TVs. This method is called a randomised trial...
Ma spesso è impossibile seguirla...
But randomised trials are not always possible... …In the case of something like caffeine in pregnancy, the issues are ethical. Imagine an experiment in which some women are told to drink nine cups of coffee a day and some are told to drink none...
Cosicché si mettono delle toppe. A questo punto la qualità della toppa è tutto...
... in most of the studies of this question, the best they can do is use statistical analysis to adjust for basic differences across people – age and education, for example...
Ci ritroviamo con una marea di lavori apparentemente simili ma in realtà molto diversi...
... There are literally hundreds of studies published in the medical literature on caffeine and miscarriage (this is the big concern with coffee during pregnancy). And from the outside, from the basic description, they all look pretty similar – comparing women who drank coffee with those who did not. But when you get into the details, into the nuts and bolts, some of the papers are pretty good and some are terrible...
È qui che interviene l'esperto. Non il medico, non l'ostetrica... in casi del genere l'esperto è l'economista...
... So we have developed techniques, statistical methods, to try to learn as much as possible from non-randomised data...
Da un’indagine sommaria degli studi disponibili appare chiara una distorsione nel senso di un eccesso di prudenza…
… I pretty quickly realised that the official recommendations were extremely cautious, so I decided that sticking to them was safe until I figured it all out. I kept myself at two cups of coffee a day and I avoided alcohol. This was added incentive to do the research fast. Ultimately, I concluded that these recommendations were not just very cautious, they were too cautious. In moderation, pregnant women should feel comfortable with both alcohol and caffeine…
Alcol:
… For alcohol, this means up to one drink a day in the second and third trimesters and a couple of drinks a week in the first. In fact, for the most part studies fail to show negative effects on babies even at levels higher than this. By a drink here I mean a standard drink – 120 millilitres of wine, 30 millilitres of hard spirits, 350 millilitres of beer. No yard-long margaritas!…
Caffè…
… Caffeine is actually a little more complicated. I ultimately concluded that three to four 235-millilitre cups of coffee per day (more than many people drink, although actually not more than I drink) are fine…
Ma perché queste distorsioni? Due ragioni: 1) troppo peso a studi superficiali e 2) paternalismo…
… So why did my conclusions differ from theirs? At least two reasons. One is overinterpretation of flawed studies. But the bigger thing, I think, is the concern (which was expressed to me again and again by doctors) that if you tell people they can have a glass of wine, they’ll have three (or one giant “bowl-o-wine”)…
***
Entriamo più nel dettaglio parlando dell’uso di alcolici.
Quali sono i danni dell’alcol al feto?…
… Foetal alcohol spectrum disorders (FASD) refer to a range of mental and physical disabilities that can result from drinking during pregnancy. Physical symptoms include low birth weight, small head circumference and facial abnormalities (flattened cheekbones and small eye openings)… There is no question that very heavy drinking during pregnancy is bad for your baby…
Uno studio esemplare…
… In one Australian study, women who binged in the second or third trimester were 15 to 20 percentage points more likely to have children with language delays than women who didn’t drink.1 This is repeated again and again in other studies…
Non ci sono molti dati sull’ assunzione occasionale di alcol…
… However, this does not directly imply that light or occasional drinking is a problem. When I looked at the data, I found no credible evidence that low levels of drinking (a glass of wine or so a day) have any impact on your baby’s cognitive development…
Usa e Ue adottano standard differenti nelle raccomandazioni sull’alcol senza ottenere risultati differenti…
… Heavy drinking is frowned upon everywhere, but many places in Europe have recommendations suggesting that a few drinks a week are fine. An occasional glass of wine or beer is much more common there. Yet there is no evidence of more foetal alcohol syndrome in continental Europe; if anything, rates are higher in the United States….
Il senso comune ci dice: molto alcol, molti danni. Meno alcol, meno danni.
Non è proprio così, per capirlo bisogna ripassare i processi biologici di base…
… When you drink, alcohol enters your digestive system and is passed into your bloodstream. Your liver processes the alcohol into a chemical called acetaldehyde and then into acetate. The acetaldehyde is toxic to other cells and depending on how quickly you drink, it can remain in your bloodstream. You share your blood with your baby through the placenta; acetaldehyde, which remains in your bloodstream, is therefore shared with the foetus. Your baby actually can process some alcohol, but not as much as an adult (obviously). If too much acetaldehyde is passed to the baby, it can get into his tissues and impact development. The key is that problems arise only if significant amounts of alcohol get into the foetal tissues…
Il problema degli studi in queste materie: etica e selection bias…
… There are no randomised trials here; the ethics are just too complicated. This means the studies compared women who chose to drink different amounts of alcohol. All these studies have the problem that the kinds of women who drink are different from those who do not…
Ecco l’esempio di uno studio attendibile…
… Among the best studies of the behaviour issue is one published in 2010 in the British Journal of Obstetrics and Gynecology.4 There are a few things that make this a reliable study: it’s pretty large (3,000 women) and they collected information about maternal drinking during pregnancy (at 18 and 34 weeks). Asking people about their behaviour while they are doing it tends to be more reliable than asking them to remember later on. The study also followed the children of these women from birth through the age of 14; they looked at behaviour problems starting at age two…. it was run in Australia, where recommendations condone the occasional drink during pregnancy…
Esito: un uso moderato dell’alcol non nuoce al feto. Perlomeno per quel che riguarda i problemi comportamentali del bimbo…
… there is no evidence that more drinking leads to higher levels of behaviour problems. In fact, the statistics in the paper show that light drinkers (that’s two to six drinks per week) are actually significantly less likely to have children with behaviour problems than women who do not drink at all….
Un altro possibile danno dell’alcol al feto è la riduzione dell’ IQ.
Uno prototipo di studio attendibile nel merito…
… my favourite study on this issue comes out of Australia. It has a lot of the same high-quality features: large study, drinking information collected during pregnancy, long-term follow-up. And, of course, the fact that it was run in Australia. This study started in the early 1980s by asking about 7,200 pregnant women about their drinking during pregnancy. Roughly 5,000 of their children completed an achievement test at age 14…
Esito: nessun danno per assunzioni moderate…
… Just as in the study of behaviour, there is no evidence here to suggest that the children of light drinkers are worse off than those of women who drink nothing. In fact, their scores are higher on average… The researchers concluded there is no evidence of worse test performance, even among the children of mums who have a drink or more per day…
Altra ricerca di qualità…
… A very similar study in England interviewed women in early pregnancy about drinking patterns and then gave their children an IQ test at age eight.6 Same result: no impact of drinking on IQ…
Ma se stiamo sulla ricerca di qualità è difficile imbattersi in risultati differenti…
… I was surprised at how consistent the findings were. It’s simply very, very difficult to find good evidence that a small amount of alcohol has any negative impact whatsoever on long-term child behaviour or IQ….
Uno studio danese, stessi risultati…
… It was a large study, run in Denmark, showing no impact of drinking up to eight drinks a week on child’s IQ at age five.7 Articles written in the popular press acted like this was a huge surprise…
Ma perché allora tanta prudenza nelle raccomandazioni?
Ecco uno studio che giunge a risultati diversi dai precedenti…
… One that gets cited frequently was published in the journal Pediatrics in 2001.8 On the face, this study looks similar to the ones I discussed above. Women were interviewed about their drinking during pregnancy and were re-contacted for a child-behaviour assessment when the child was about six. The study is a bit smaller (only about 500 kids)… When the authors compared women who didn’t drink during pregnancy to those who had one drink or less per day, they found more evidence of aggressive behaviour (although not of other behaviour problems)…
Il difetto: si confrontano gruppi disomogenei…
… One of the very nice things about the previous studies – the ones I liked – was that the groups of women who drank different amounts were not that different in other ways. If this were not the case, we would be worried that the other differences among the women – not the drinking – were responsible for the behaviour problems…
In questo senso lo studio dei pediatri è altamente deficitario…
… This last paper failed on this count. In this study, cocaine use during pregnancy was reported by 18 percent of the women who didn’t drink at all and 45 percent of the women who had one drink per day. Presumably your first thought is, really?…
Possiamo buttare tutto nel cestino.
Un altro possibile problema per chi beve in gravidanza: aborti spontanei e parti prematuri.
Evidenza su aborti spontanei…
… In the case of premature birth, the answer is no. You can see this in studies in both Denmark and Italy (among other places). In the Italian study, women who drank up to one drink per day were actually less likely to have premature babies than those who did not drink at all…
Evidenza su parti prematuri…
… The evidence on miscarriage in the first trimester is a bit more mixed. A review article from 2007 summarised a number of studies. Several suggested there was no relationship between light drinking (in their case, up to one drink a day) and miscarriage. There were studies that suggested a link in particular subgroups (like among smokers), but the review dismissed these as largely unreliable. They concluded that there was no strong evidence for (or against) a relationship between light drinking and miscarriage…
Sembra che non esistano collegamenti, almeno quando si beve in modo moderato.
Ma ecco comparire uno studio con risultati originali…
… a new study released in early 2012 that analysed the behaviour of almost 100,000 Danish women and found that even light drinking (two or more drinks a week) was associated with an increased risk of miscarriage in the first trimester…
Difetto: non controlla con la nausea. La nausea è sintomo di gravidanza ottimale e, al contempo, neutralizza la voglia di bere. Bisogna tenerne conto. Questo studio non lo fa…
… This study wasn’t perfect; they were not able to control for nausea, which other studies have shown to be an important mitigating factor (women who are nauseous drink less and nausea is a good sign about a healthy pregnancy – more on this in the discussion of coffee)…
Cestino.
Lo stereotipo da sfatare:
… One phrase I kept coming across was “no amount of alcohol has been proven safe”…
Tutto in eccesso fa male, anche le banane. Ma noi non diciamo: “meglio non mangiarle affatto”…
… too much of many foods can be bad. If you have too many bananas (and I mean a LOT of bananas), the excess potassium can be a real problem. But no doctor is going around saying “No amount of bananas have been proven safe!”…
In poche parole: l’evidenza che assolve il bere moderato è la medesima che condanna il bere pesante. Non si puo’ accogliere l’una rigettando l’altra…
… what is all this evidence if not proof? It’s exactly this type of evidence that leads us to conclude that binge drinking is problematic….
