ABNORMALITIES IN MECHANISM.

The most frequent and important are (1) backward rotation of the occiput and (2) excessive rotation of the breech. Backward rotation of the occiput is very exceptional, and the mechanism now differs as the head remains flexed or becomes extended. When flexed, the chin, face, forehead, anterior fontanelle slip out under symphysis in the order named, and the head is delivered. When extended, the chin catches upon the symphysis, the head is extremely extended and is born by the occipital protuberance, small fontanelle, cranial vault and face slipping over the perineum. The following rules for managing these cases should be remembered: If flexed, the body of the child should be carried downward. If extended, the body should be carried upward over the mother's abdomen. Excessive rotation of the breech occurs as the result of prolapse of posterior extremity, and is of no great practical importance.

SHOULDER.

Transverse position of the child in utero resolves itself into a shoulder presentation as the result of uterine contraction when labor begins. Shoulder presentations are classified according to the position of the back and head. When the head is to the right the back can be in front or behind. The same is true when the head is to the left. The back is directed anteriorly twice as often as posteriorly, and the head more than twice as often is found toward the left.

Diagnosis.-Abdominal palpation reveals the foetus in a transverse position. The heart-sounds are more distinct at a point corresponding to the interscapular region of the child, and sometimes cannot be heard. Digital examination shows the characteristics of the shoulder, viz., axilla, clavicle, spine of scapula, acromion process, head of the humerus, ribs.

Causes.-1. Abnormalities in the shape and position of the uterus, as pendulous abdomen; uterus bicornis; kyphotic spine; uterine fibroid and other abdominal tumors; multiple pregnancy (in twin pregnancies the shoulder presents once in 22 cases).

2. Conditions preven engagement of cephalic or pelvic

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extremity, as deformity of the pelvis ; abnormally large child; monstrosities; placenta prævia.

3. Abnormal mobility of the fœtus, as occurs in hydramnion, after foetal death, or in premature birth.

Mechanism.-Strictly speaking, there is no mechanism of shoulder presentations. The course of these cases is impaction of the shoulder, ascension of contraction ring, destruction of the foetus by prolonged pressure, and death of the mother by rupture of the uterus or exhaustion. As a matter of fact, however, nature can in exceptional cases effect delivery in one of three methods :

1. Spontaneous version. The transverse position converted into a longitudinal by uterine contraction.

2. Spontaneous evolution. The breech slips past the shoulder and is delivered.

3. Body doubled up (corpore reduplicato).
Treatment.-Version.

MECHANISM OF THE THIRD STAGE OF LABOR.

Theories of Separation:

(a) Placental area diminished.

(b) Placenta pushed off.

(c) Separated by retro-placental clot.

The first probably correct.

Theories of Expulsion:

(a) Edgewise (Matthew Duncan).

(b) Like inverted umbrella (Schultze). The last probably correct.

ABNORMALITIES.

(a) Retention.-Occurs frequently. Hemorrhage is slight. The placenta is situated in the dilated lower uterine segment and upper portion of the vagina.

Treatment. Proper application of Credé's method of expression. Sometimes atmospheric pressure determines its retention; a finger then may be hooked over one edge to pull it down.

(b) Adhesion.-Occurs once in 312 cases, and is usually partially detached.

Diagnosis. -Credé method of expression fails and there is alarming hemorrhage.

Treatment.-Pass the hand along the cord to the fundus and complete the separation with the finger-tips, using them as a paper-cutter; pinch through any dense spots of adhesion, close the fingers about the placenta, stimulate the fundus by friction through the abdominal wall, and allow uterine contractions to expel the hand and contained placenta.

Prognosis. Many die from hemorrhage; seven per cent, from sepsis. Most exceptionally the placenta can be retained in utero for months without doing harm. Among the rarest anomalies in regard to the placenta during labor are hernia of the placenta through the muscular coat of the uterus during labor, and prolapse of the normally situated placenta. The latter is most likely to happen with twins, after rupture of the uterus, or in premature labor, but it has been observed at term, without injury to the uterus, and in a single pregnancy. There is not necessarily profuse hemorrhage nor other disadvantage to the woman, but the foetus dies unless it is extracted at once.

Obstetric Operations.

Induction of Premature Labor and Abortion.

ABORTION.

When performed before viability of child (180th day).

Indications.-When the patient is a subject of disease originating in or aggravated by pregnancy and life endangered thereby, viz.:

1. Pathological Vomiting.-Only after all known remedies and rectal alimentation fail.

2. Grave Albuminuria.-As when cedema, headache, casts, failing vision, etc., threaten eclampsia.

3. Death of the Embryo or Foetus.

4. Certain Intrauterine Diseases.-As acute hydramnios and cystic degeneration of the chorion villi.