Generally speaking, kapag umiiyak po sya. Kaya very challenging and frustrating kasi di mo sure among the numerous possible reasons why they're crying-- gutom, diaper, burp, mainit/ malamig, antok or may sakit.
Also having fever, diarrhea, hindi nagdedede, etc. are also symptoms of something more serious. Yung primary caretaker ni baby ang best rin na makapagsasabi if something is not right/ normal sa kanila.