That probably reflects the fact that Europeans tend to drink far more than Americans anyway. Over here a pregnant woman is far less likely to drink than a not pregnant woman. (Page 12 of linked PDF)

http://www.ons.gov.uk/ons/rel/ghs/opinions-and-lifestyle-sur...

http://www.hscic.gov.uk/catalogue/PUB14184/alc-eng-2014-rep....

(I'm on mobile at the moment so I'm having trouble finding rates for dependant drinkers who don't cut down while pregnant. That first link suggest 2% of pregnant women don't cut down or even drink more, but that doesn't tell me how much they used to drink - someone drinking one glass once a month moving to one glass once a fortnight has doubled their consumption but probably isn't doing any harm)

It's known and accepted in the UK you can't drink/smoke when pregnant. It's social taboo. I've never seen it in the UK.

"never seen it" is not the same as "it doesn't happen".

Smoking during pregnancy has been on the decline for years, and 2014 was the lowest it's been.

http://www.hscic.gov.uk/article/4788/Prevalence-of-mothers-s...

> Today's report shows the prevalence of women who classed themselves as smokers whilst pregnant fell to 12.0 per cent (75,910 out of 632,960 maternities)3 from 12.7 per cent (83,490 out of 658,110 maternities) in the previous year4, and this continues the steady decline from 2006-07 when this was 15.1 per cent.5

Lowest on record, but still 12% is pretty high. I suspect the reason, as you say, is the taboo. A pregnant woman who smokes faces a lot of judgement, so she's probably going to smoke at home.

"It's social taboo. I've never seen it in the UK."

It goes on but not so much in public though.