Hard and uneven breast implants after pregnancy. Is the hard one likely due to contracture?

This does sound like a capsular contracture.  Sometimes aggressive massage can do the trick, but usually this requires surgical intervention to correct. You will need to talk to your surgeon about the timing of correction.

From your description it sounds as though you may have developed a capsular contracture. After your breasts of resume there normal physiology after pregnancy you can visit your plastic surgeon for therapeutic options.

Congrats on your family addition. You did not say just when the breast became "hard". If it was rather gradual, I think yout guess is correct and it is capsular contracture. If it was sudden, you have to think of direct trauma to the one breast and perhaps the accumulation of fluid around the implant (seroma), which can distended the tissues and make that breast feel tight and firm. You might want to check on that by having a sonogram, but get in to see your plastic surgeon for an exam and recommendations on how to proceed. Meanwhile, you might want to wear some good support, and perhaps limit the use of that arm until your surgeon can advise.