Pediatrics is generally amongst the more rapid journals in getting out responses. They always get me my rejections back to me in a hurry. 🙄 That typically means 4-6 weeks from submission. However, as with every journal, a tardy reviewer or holidays, or a conflict in views between reviewers can extend the time. As a reasonable guide, if you haven't heard in about 8 weeks, you should "nicely" query the editor as to what the delay is.