Hello, Sun.
I quit being domesticated some time back. However, on cleaning the ceiling, it mostly depends on why you are cleaning it and what kind of material the ceiling is.
If you are trying to remove pet smells and smoking odors from the house, then, using a cleaning solution of white vinegar and plain water, and with a damp sponge, wipe the ceilings, walls, and woodwork. Dry the area you are washing as quickly as possible as painted sheetrock, painted plasterboard, and wood will soak up and swell from excess water -which you don't want.
White vinegar and water solution is also good for cleaning crayon, spaghetti stains, and such off the walls and ceilings.
If you are trying to clean up spiderwebs, dust curtains and that other grungy gunk that seems to appear out of nowhere sometimes, then use a dusting spray like Endust on the end of a broom and sweep the ceiling and walls.
Otherwise, vacuum the ceiling and if it still needs sprucing up, paint it.
P.S. Since you are pregnant, then stay away from cleaning chemicals and paint. And, stay off ladders and chairs and such to get up high enough to wash the ceiling. Get a man to do that stuff - it is one of the things they are good for.