My wife is 37weeks pregnant she had sonography 1days ago. doctor says all is good but they found some large cyst near bladder.iam worried please help?

Fetal abdominal cyst: I presume you are talking about your baby, not your wife's bladder. If you are expecting a little girl, an ovarian cyst is a likely explanation of little concern (although it could twist/rupture causing acute neonatal abdominal pain). If it is a boy, more serious anomalies could be at work, such as sacrococcygeal teratoma, cloacal malformation or imperforate anus. Seek maternal-fetal medicine care.