Oxytocin response, withdrawal, and reinforcement of defense mechanism of the human uterus at midpregnancy

Urinary Excretion of Oestriol and Pregnanediol During Bougie-Induced Abortion in Mid-Pregnancy

“…Opinion varies concerning its effect on placental function. Bengtsson & Csapo (1962) state that the uterus starts vigorous contractions when it is freed from the restraining influence of placental progesterone, and Bengtsson & Stormby (1962) noted extensive damage^of the placenta delivered by this method. Other investigators, however, have found placental damage from saline to be slight (Christie et al 1966), with no significant change in urinary output of pregnanediol during this treatment (Klopper et al 1966).…”

“…In recent years, attention has been focused on the induction of labour by intra-amniotic injection of hypertonic saline at mid-pregnancy. Some investigators think that this method damages the placenta and that the resulting withdrawal of the restraining effect of progesterone precipitates uterine contractions (Bengtsson & Csapo, 1962;Bengtsson & Stormby, 1962). Others failed to find evidence supporting this hypothesis (Klopper, Turnbull & Anderson, 1966;Christie, Anderson, Turnbull & Beck, 1966).…”

The luteo-placental shift, the guardian of pre-natal life

“…1). However, when intra-uterine pressure was recorded transabdominally in patients more than 14 weeks pregnant (Bengtsson & Csapo, 1962), it was found that a response to oxytocin could always be obtained, though massive doses (128 mU/min) were required in the second trimester to induce 18 mmHg pressure (Fig. 1).…”

Hormones and Metabolism in Pregnancy

“…It will probably ibe necessary to do combined studies of blood hormonal values (e.g. oestrogens and aldosterone) and total water and electrolyte values in normal and abnormal pregnancies in order to determine whether there is a primary water or sodium retention in pre- Intra-amniotic injection of saline causes abortion or labour and ,it has been claimed (Bengtsson and Csapo, '1962) that the injection damages the placenta to such an extent that its production of hormones is greatly reduced. The "progesterone iblock" is thus removed from the myometrium, and labour begins.…”

“…of ,mercury, twice as high as that in full-term labour. Bengtsson and Csapo (1962) believe that such high ,pressures resulted from the complete withdrawal of the "progesterone block". Anderson, Turnbull and Murray (1966) have demonstrated, however, that relationship between myometrial tension and amniotic fluid pressure during a contraction depends on the size of the uterus; the smaller the uterus, the higher the pressure resulting from the same myometrial tension.…”