Generally a queen will give birth about 65 days from the first day of mating although this can vary by a few days. Before 61 days kittens will usually be too premature to survive even if they are born alive. So from 61 days onwards you should keep a close eye on the queen by day and, if possible, night. Although rather antisocial, a lot of queens do give birth at night! Some queens get milk two or three days before giving birth which can be a very helpful indicator.
Many queens will require, or at least appreciate, some help with the delivery especially if they are maidens or expecting a large litter: Burmese are renowned for large litters but four to six is the norm. Unlike humans they haven’t been to classes or read books and giving birth can be a confusing or even frightening time for some of them. Even old hands may be pleased to have help.
The first stage of labour usually involves quickened breathing often accompanied by rhythmic purring. This stage may last for many hours. It is wise at this point to confine the queen to a quiet, warm room (minimum of 72F or 22C) with her kittening box, which need be nothing more than a large cardboard box. Queens should continue to have access to water and a litter tray but some refuse food whilst others will eat heartily. As labour progresses there will some vaginal discharge.
The second stage of labour begins when the queen starts to have contractions. Initially there may be long intervals between contractions but these gaps shorten until just before delivery when they occur about every 30 seconds.