This is probably due to the hormone-induced dilatation of small blood vessels during pregnancy. So long as you have no other symptoms, I do not think this is anything to worry about. Other eye problems should be taken more seriously during pregnancy. Sudden visual disturbances – blurred vision, flashing lights, dark spots – may be related to a dangerous rise in blood pressure. Always report these symptoms urgently to your midwife or GP, even if your blood pressure has hitherto been normal.