The easy answer is even though it's an artificial induction with artificial oxytocin you would think "it's the same hormone, why not?" but it goes Much deeper than that. First of all, I will explain what happens in a pit induction as opposed to natural labor and then explain the risks involved.

When a woman goes into labor on her own, it is her baby who initiates labor. Thus when baby is "ready" contractions start and they will strengthen, become longer and closer together as time goes on. If baby is finding it difficult labor will slow or even stop as in posterior presentations and long prodomal labors. Baby is using the contractions to help turn and get in a good position. With each contraction the long Muscle bands running vertically (picture mom sitting upright on a birth ball) pull the cervix open as the strong mass of muscles at the top of the uterus push down. The horizontal muscles tighten, but just a bit to make sure baby Is aligned properly and help guide baby down.

As labor progresses the mass Of muscle at the fundus gets thicker because it is pulling the cervix up and away from the birth canal and the baby is moving lower. Thus when transition hits and baby moves two or three stations quickly after the cervix is dilated, a lull in the contractions happens because the uterus has to "catch up" to the baby. When second stage hits, all the uterine muscles push and guide the baby through. Third stage the umbilical cord stops pulsating as the uterus clamps down because the muscles cross each other and as they contract they cut off the blood supply to the uterus and it sloughs off the uterine wall to be expelled.

OK now let's look at pit induction. A baby not yet ready for labor is slowly starting to feel contractions. That is OK because baby is used to uterine contractions throughout the pregnancy. They become stronger and baby is still fine, as he is guided down and uses his head to dilate the cervix.

But what he notices is that it isn't only the longer muscles that are contracting, but also the horizontal ones, so he is not just pushed down, but squeezed hard from all sides. In artificial induction's the entire muscle contracts evenly, instead of just the fundal muscles pulling the cervix open. It is more difficult for baby because he isn't guided down as easily as would be in an uninduced birth. Contractions often are longer with less of a break between so baby has less time to recuperate between, and If he is posterior or asynclitic, it would be difficult to rotate or turn Into a good angle, which is very common because baby isn't ready for birth yet.

Regardless of this, induced births, once established, often go quicker because the uterus is working much harder than it would normally. The cervix will often dilate quicker and labor will be shorter. This can really distress a baby, especially if he has to mold quickly... and if he is posterior a LOT of molding will occur in order for his head to fit. OK,
You have the picture... let's look at the risks.

"Dr. Caldeyro-Barcia concluded (after a collaborative study in twelve Latin American medical centers) that in oxytocic-induced labors, even with proper precautions--such as the lowest effective dosage given and proper monitoring of mothers--almost seventy-five percent of the mothers' uterine contractions
were shown through fetal heart monitor tracings to result in a reduction of oxygen to the baby's brain." (Immaculate Deception, 1975)

"The mother should never be left alone while the oxytocin infusion is running. Uterine contractions must be evaluated continually and oxytocin shut off immediately if contractions exceed one minute in duration or if The fetal heart decelerates significantly the frequency, intensity, and duration of contractions, and uterine tone between contractions must note exceed those of normal spontaneous labor. Oxytocin is a powerful drug, and it has killed or
Maimed mothers through rupture of the uterus and even more babies through Hypoxia from markedly hypertonic uterine contractions." (Williams Obstetrics)

"The Golan study concerned ninety-one cases of uterine rupture during a five-year period. Of these, 61 occurred in normal uteri while 32 were Found in patients who had undergone a previous section. There were nine Maternal deaths, and all occurred in the group of mothers who had not had Previous cesarean surgery. The fetal mortality was also much worse for the women without previous cesareans. The fetal mortality for the previous Cesarean group [who experienced uterine rupture] was twenty-two percent, while it Was more than triple, or seventy-four percent, in the unscarred group [who experienced rupture]. The ruptured uteri in the normal, unscarred group were, for the most part, associated with oxytocin administered during labor." (Joy of Natural Childbirth, 1994)

Both the American and Canadian OB/Gyn Organizations state that artificial induction or augmentation should not be used for VBAC or "trial of labor" patients because of the risks of uterine rupture.