Nope, very true.
When I said younger, I wasn't talking about 18-20. So yes, back in the day, it was not custom for chicks to have kids in their younger teens. Again, hence why there are grandmas in their early to mid 40's being more common.
Speaking of back in the day, it was considered shameful for a teenager to get knocked up and she was sent away to live with an extended family member.