They didn't say during pregnancy. Cows only produce milk after giving birth to a calf, so they're regularly inseminated.
I think a lot of people don't realize we're hijacking their reproductive systems, instead assuming cows constantly produce milk.
One could argue there's more suffering in a glass of milk than a steak, which makes ethical vegetarianism flawed despite its good intentions.
> One could argue there's more suffering in a glass of milk than a steak
What I find quite bizarre that in India (where I am from) milk is considered ethically vegetarian whereas unfertilized chicken eggs are not.
But the weirdest experience I have ever had was at the main Google cafeteria. One gentleman with a steak on his fresh plate was quizzing the attendant at length to be sure that the mashed potato was vegan. After many months of thinking I found a plausible reason.