Your medical practitioner (doctor or midwife) should check your weight during every appointment, roughly every 4–5 weeks. This way, you'll be able to monitor your weight and its changes throughout the entire pregnancy. Regular check-ups let you act quickly if you're gaining more or less than the recommended weight gain range. 
If you wish to monitor your weight even further, you can easily weigh yourself every day. Make sure to do this at the same time of the day, before having your meal. Consult your medical practitioner if you gain more than 0.5 kg (1.1 lb) per week or if you're suddenly losing or gaining a lot of weight, especially later in pregnancy.
Remember — gaining too much or too little weight in pregnancy can both increase the risk of serious complications! Read more