This is a great phrasing! Maybe that's part of why it bugs me so much - I know I tend to have less-than-common reactions to things like this, but for once everybody seems to be agreeing with me that this was just Not Quite Right in terms of threat and symbolism.

I mean, honestly, in Natasha's situation, I personally would be more afraid of NOT being sterilised/openly told that fertility was out of the question; otherwise the idea of being a broodmare for the people who control me would be a very obvious interpretation! And I can think of few more horrifying ideas than that one - imagine having to assume that your one-day daughter would be held as a guarantee of your behaviour... not to mention she'd be put into the same murderous training and abuse that you've undergone.