I think it depends on the OBs. Some find it important, others don't. It can be quite helpful in later pregnancy to detect pre-eclampsia. Other than that the weight gain is often nothing significant. Some gain a few kilos, others 20 or more (I am sure I'll gain 20 kg). It might be useful for yourself a) for future pregnancies, b) for losing the weight afterwards again. Other than that I think it's really a personal preference.

Snowy
(who so far has gained a shocking 8 kg)