A 26-years old primipara experienced a laparotomy with thrombectomy because of pelvic vein thrombophlebitis and cavathrombosis 18 days after ambulant water-birth. The pelvic vein thrombophlebitis is a potentially life-threatening complication in puerperium and to our knowledge, this is the first case reported after water-birth. Even after ambulant childbirth those rather rare complications are able to appear. To think of such events makes professional help possible in time.