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How might care in VBAC labors differ?
VBAC labors shouldn’t be handled any differently from labors with an unscarred uterus with one possible exception. The most reliable symptom that the scar has opened and is causing problems is a sudden drop in the baby’s heart rate. For this reason, Dr. Bruce Flamm, preeminent VBAC researcher, recommends continuous electronic fetal monitoring (EFM). Others have argued that symptomatic scar separations happen no more often than other unpredictable obstetric emergencies (7). If women generally have not been shown to benefit, we should be cautious about subjecting women with prior cesareans to EFM’s disadvantages. Here are some unjustified ways that doctors may manage VBAC labors:
Refusal to allow an epidural: At one time doctors thought an epidural might mask the pain of the scar separating, but pain has been shown not to be a reliable symptom, and experts have long since agreed that epidurals should be permitted (13). That being said, epidurals pose one problem peculiar to VBACs. Some babies will experience an episode of slowed heart rate, and a drop in the fetal heart rate is the most reliable symptom of the scar giving way (15).
Routine IV: IVs cause pain, decrease mobility and can cause fluid overload. Fluid overload can lead to a host of physiologic problems, some minor, some major, in babies and mothers (15). If you feel uncomfortable refusing an IV, compromise on a heparin lock. With a heparin lock, the IV catheter is inserted, but it is only connected to a short piece of tubing that is taped to your hand or arm. It frees you from the IV pole, but an IV can be plugged in at any time.
No oral intake: You should at least be allowed to drink clear liquids. Hunger and especially thirst increase discomfort. Dehydration and starvation can diminish contraction strength and may make the baby’s blood more acidic, a symptom of fetal distress (15).
Intrauterine pressure monitor: The theory is that the scar giving way will decrease uterine contraction pressures. However, an analysis of 76 cases of symptomatic scar separation found that in no case did monitoring contraction pressures internally diagnose the problem (31). Another study simulated scar breakdown in twenty women by recording uterine pressures in laboring women before and after incising the uterus during cesarean section (5). The monitoring device failed to show pressure changes in any of the women. Internal contraction monitoring increases the risk of infection, and in rare cases, the catheter can injure the placenta, pierce the uterus, or become entangled with the umbilical cord.
Manual exploration of the uterus after the birth: There seems to be little value in identifying symptomless scar windows because they don’t seem to pose a risk in subsequent pregnancies. On the downside, the internal examination is extremely painful. The procedure also could increase the risk of infection or convert a small, harmless gap into a problem. In the sole reported case of maternal death due to bleeding from a scar that gave way, the uterus had been explored after the birth, but the rupture was missed (6).