[PA] Job Offer, Relocating & Pregnant

My family and I are trying to relocate before I give birth. We are moving due to my past with postpartum depression and it's closer to family so we'll have more help with a toddler. With this, comes finding a new job. I got a job offer today for my literal dream job to start advancing my career I've been wanting in Pittsburgh. How should I go about possibly telling them I'm pregnant? It's been a process trying to figure out when I can even start because I need my husband to have a job as well and he's heard nothing. The start date they offered was Feb 2. I need to take maternity leave in May/end of April. During the interview process I mentioned several times needing the flexibility in case relocating has its glitches and the start date needs to be adjusted. The start date depends on when my husband finds a job too. The issue is if he cant find one before April/May there will be another delay due to maternity leave. The job offers 12 weeks of short term disability. The location is in Pittsburgh PA which i know is an at will stare. Any advice would be super helpful.