the uterus contracts ,the contractions are followed by a stimulus the patient may describe these as menstrual cramps ,blood may gush or ooze depending on the stage the cervix remains closed.it is said to be threatening .abortion becomes inevitable when the uterine contractions strengthen ,vaginal bleeding increases and the cervix becomes soft and the cervical os progressively dilates .the expulsion contents follow ,should the foetus ,membranes and placenta be completely expelled ,the abortion is said to be complete .incomplete abortion is when some of the products of conception are retained .