Am 17 weeks pregnant having severe constipation, is miralax (polyethylene glycol) safe to use during pregnancy?

I prescribe it. There are many options for constipation in pregnancy. First involves making sure you are taking enough water and fiber in your diet. Metamucil or fibercon can be used in addition to natural sources of fiber. Colace twice daily often helps as well. But for those patients who don't see improvement on that regimen, either a dulcolax suppository or MiraLAX (polyethylene glycol) is the next thing i typically suggest.