الفهرس 
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Abstract
In spite of past reports that vaginal examinations or instrumentation during pregnancy did not contribute to abortion, clinical experience in certain circumstances strongly suggests the opposite. Tindall (1987) reported that in women prone to abortion, any mechanical stimulation to genital tract such as occurs during coitus or during routine vaginal examination may be enough to precipitate expulsive uterine contractions.
Early reports postulated that stimulation of the female reproductive tract caus oxytocin to be released from the posterior pituitary with a consequent increase in the uterine niyometrial electrical activity. Ferguson (1941) provided early support for this hypothesis with the finding that the distention of the cervix causes enhanced contractions of the uterus after a latent period long enough to imply a hormonal mechanism. Deberckere and Peeters (1960) and Deberckere et al., (1961) have also shown that vaginal distention provides the same changes in milk duct pressure as the intravenous injection of 50 mu of oxytocin in lactating ewes as well as in lactating cows.
In addition, Chard and Gibbens (1983) reported that the procedure of amniotomy in women for induction of labor was associated with a spurt release of oxytocin. They also concluded that the main stimulus to this release was vaginal distention and the same mechanism probably accounts for the increase in maternal oxytocin during the expulsive phase of labor which increases the power of uterine contractility.
The most convincing support for the view that vaginal manipulation increases secretion of oxytocin has come from observations of milk ejection responses in lactating animals and little studies seem to have been done in non lactating, non pregnant animals. The first study on the effects of vaginal distention on the level of oxytocin in plasma in non lactating normally cycling animals was done by Roberts and Share (1969). The results of their study showed that vaginal distention is effective in increasing the concentration of oxytocin in the plasma not only of lactating but also of normally cycling ewes. However, distention of the vagina of the pregnant ewe, results in a transient decrease in the concentration of oxytocin in the plasma.