Under the spouse visa your Mrs is entitled to free nhs treatment and like you say when pregnant free prescriptions and dental treatment. She will also be entitled to free dental treatment up until your babies first birthday (my wife made the most of this and went to her dentist more times in that year than I've been in a lifetime She will be issued with a exemption card (like a little credit card) which she can take to any appointments and I think they put an expiry date of 1 year from your babies due date
No doubt you will be getting the "bounty" packs at various stages of her pregnancy, again no problems. From what I can remember (out boy is 1.5yo now) the packs contain things like discount vouchers for shops like mothercare, boots etc. you also get things like samples of washing powder, baby wipes, baby towels, stuff like that.
Also looking ahead a little, when the baby is born your wife can't claim child benefit but you as the father can claim. That's what I did.
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