Tuesday, 12 April 2011

Scaring women - easy, profitable, and fun

According to the Telegraph:
"Researchers say there might be no safe limit for the amount of alcohol a pregnant woman can drink without endangering her unborn child

"However, now researchers in Ireland have found evidence that women who drink up to five units a week, equivalent to two 175ml glasses of red wine, could be putting their children at risk of fetal alcohol syndrome.

"The study found three cases of fetal alcohol syndrome "one each in the low, moderate and high consumption groups". The fact there was one in the low alcohol consumption group led the researchers to question the theory that light drinking had no effect on a baby's health."

Well this is the paper, in BMC Pregnancy and Childbirth, the abstract sums it up pretty well:
"A cohort study of 61,241 women who booked for antenatal care and delivered in a large urban maternity hospital between 2000 and 2007. Self-reported alcohol consumption at the booking visit was categorised as low (0-5 units per week), moderate (6-20 units per week) and high (> 20 units per week).

"Of the 81% of women who reported alcohol consumption during the peri-conceptional period, 71% reported low intake, 9.9% moderate intake and 0.2% high intake.

"High consumption was associated with very preterm birth (< 32 weeks gestation) even after controlling for socio-demographic factors adjusted OR 3.15 (95% CI 1.26-7.88). Only three cases of Fetal Alcohol Syndrome were recorded (0.05 per 1000 total births), one each in the low, moderate and high consumption groups."
If we assume all births were single babies (since most will be, and the twins and higher number births will not affect the numbers much) that's rates of foetal alcohol syndrome (FAS) of .0023%, .016%, and .82% in the low, moderate, and high risk groups respectively. That gives a relative risk of FAS in the high alcohol consumption group of over 300x the low consumption group.

Interestingly the overall FAS rate in the study is 1/10th of the usual estimated rate, probably because this was only those infants detected in the baby check in hospital. So, in conclusion, there were only 3 cases of FAS in this study which is both very low, and also too small to really draw too many conclusions. Any claim about low alcohol consumption causing FAS is basically a case report of one child that occurred with a rate of .0023%.

Importantly, we have to remember that FAS is believed to be due to heavy drinking throughout pregnancy, and the study did not record this, only alcohol consumption early in pregnancy. If the mother of the FAS child in the low alcohol group was under-reporting her alcohol consumption or went on to drink more heavily throughout pregnancy we have no evidence for a risk of FAS in low alcohol consumption in this study.

So did the authors really cause such an unnecessary scare by claiming that low alcohol consumption causes FAS as the Telegraph reports? Well here they are in the paper:
"This suggests that the mothers of the first two infants [the low and moderate alcohol consumption cases of FAS] may have under-reported their alcohol intake at the time of booking as FAS is unlikely to occur at lower levels of alcohol intake" [my emphasis]
Apparently not. So just another PR/journalist manufactured scare because worrying women about pregnancy, childbirth, and child rearing is easy, profitable, and fun.


Neuroskeptic said...

This also assumes that the "low alcohol" case of "FAS" was actually that, not a) a woman lying about her drinking or b) something unrelated, maybe a genetic disorder, that causes FAS-like effects.

Allo V Psycho said...

I'd be curious to read any associated Press Release before blaming the reporters alone. Yes, they shouldn't recycle PRs but I've seen some which are highly misleading, and where the drafters must share some of the blame.

pj said...

That's what I meant by 'PR/journalism', the journal in particular, or the authors' institution may have played up the story.