Tumors in or near the uterus may be obstacles to delivery or they may through malignancy endanger the woman's life. The commonest tumors complicating pregnancy are fibroids, cancers, and ovarian tumors, especially cysts and dermoids, but tumors of other kinds are not frequently met. Schauta, in 111,112 pregnant women, found fibroids in 86, one in 1292 cases; Pinard, in 13,915, found 84, one in 165 cases; Pozzi, in 12,050, had 83, one in 133 cases; in St. Petersburg, in 13,076 deliveries, there were only 4, one in 3269 cases; and in the Charité in Berlin, 6 in 19,052 births, one in 3175 cases. The ovarian cyst in pregnancy is rarer than the fibroid--5 in 17,832 births, one in 3566 cases, in the Berlin Frauenklinik. Cancer of the cervix also seldom appears--once in about 2000 cases. Other very rare conditions, related to these, are polyps of the cervix, enlarged and prolapsed kidneys, extrauterine pregnancy combined with intrauterine, echinococcus cysts, parametric abscesses, cancers of the rectum, rectal strictures, tumors of the bladder, stones in the bladder, tumors of the pelvic bones or cartilages, and tumors of the vagina or vulva. Fibroids, called also fibromyomata, fibromata, and myomata, in the uterine muscle or adnexa commonly enlarge during pregnancy, and if they are big enough and low in the pelvis may block the parturient canal. These tumors may suppurate, grow gangrenous, or take on red degeneration; they may cause abortion, peritoneal adhesions, pain, or hemorrhage; simulate threatened abortion; bring on retroflexion of the uterus, placenta praevia, abnormal presentations, sometimes weak pains or pains so strong as to rupture the uterus, and they may check contraction after delivery so as to start hemorrhage. They may so kink the uterus as to incarcerate the placenta and cause sepsis. The percentage of degeneration in fibroids taken generally is 22, according to William Mayo.[113] [113] _Jour. Amer. Med. Assoc._, March 24, 1917. Myomata often obscure the diagnosis in pregnancy. The tumor may be mistaken for a twin child, or vice versa. A large symmetrical interstitial myoma may be mistaken for pregnancy, or vice versa. Sometimes, even after the belly has been opened, it is difficult to be sure whether the condition is pregnancy or a tumor. As eminent a surgeon as Deaver says this diagnosis cannot always be made by any one no matter what his experience.