Waiting on my birth mother

I found my birth mother and sent her a letter. I included pictures of myself  hoping to spark her interest, I guess it didn't work. It's hard for me to understand how a person can carry a baby for 9 months, give birth to them, see them as an infant and then have no thoughts of them every. I need to have hope that one day she will send a letter or email or maybe, just maybe call. It's stressful waiting.