Cervical Incompetence and Cerclage - 6 - Evaluation and Decisions in Midtrimester
However, let me start again with a situation that I consider to be relatively ‘straightforward’ – the patient who presents at 18-22 weeks with little or no cervical length and membranes bulging near, at, or even through the external cervical os. This patient is going to usually deliver imminently and I have selected the range of gestational ages because the baby is previable at this point (although 22 weeks is getting very close to that as a possibility) and the importance of this will become more apparent in a moment.
One does not have a lot of time to make decisions under these circumstances, but the patient needs to be adequately evaluated before a recommendation for therapy can be suggested. The main focus of the evaluation is to try to establish whether or not overt intrauterine infection (chorioamnionitis) is driving the process – and that is sometimes not as easy as one might think – because if it clearly is, then the only therapeutic choice is delivery. When a patient in this situation hits the door, the first steps we take after obtaining vital signs (blood pressure, pulse, temperature) include: a complete blood count with differential; blood type and screen; a catheterized urine analysis and culture; cervical cultures for gonorrhea and Chlamydia (if these can be obtained safely – otherwise they may be deferred); a vaginal slide to look for evidence of bacterial vaginosis; and vaginal fluid to screen for ruptured membranes; an ultrasound to assess fetal size, evidence of anomalies, and Doppler flow studies if indicated; and, oftentimes blood chemistries to include electrolytes and liver function tests.
The patient is then connected to a uterine contraction monitor if that is possible, although one must realize that most patients will have contractions or some degree of uterine irritability once the cervix has gotten to this stage and I have found this to be only a relative contraindication to treatment. If cervical change has been documented by ultrasound, I usually do NOT perform a digital exam on the cervix – saving any further evaluation in that regard until the patient is in the operating room if it appears a cerclage will be attempted.
Although I do not routinely perform an amniocentesis on all patients in this situation, there are many providers who do and so do I in selected cases. When amniocentesis is done, the primary purpose, again, is to look for evidence of overt intrauterine infection (when this is not clearly apparent by physical examination or laboratory studies) as might be reflected by the presence of white blood cells, low amniotic fluid glucose levels, and positive amniotic fluid cultures. We do not routinely screen for inflammatory cytokines in the amniotic fluid at this time.
The next step is to put the pieces of the situation together, have a frank discussion with the patient and her family, and provide options for management. If the patient has a fever (not related to a urinary tract infection), and/or high white blood count and differential suggestive of acute infection, and/or a tender uterus with painful contractions and pain between contractions, and/or a purulent cervicovaginal discharge, the presumptive diagnosis is chorioamnionitis and the only safe option is to allow delivery – indeed, delivery is inevitable regardless of what we might do to intervene. The baby is previable and the mother’s life and future fertility may be at risk. I usually begin broad spectrum antibiotic coverage and, if necessary, recommend augmenting the labor process with oxytocin or misoprostol.
If overt infection is not clearly present, then the patient has basically two options – undergo ‘conservative management’ and wait to see what happens or undergo cerclage. I make several points during the counseling session: if delivery appears imminent and remote from fetal viability, she is told this bluntly (or if some cervical length remains and we honestly cannot predict when delivery might occur, she is also told this); if a cerclage is placed, it may precipitate delivery; if infection develops, regardless of the decision to perform cerclage or not, the "ballgame is over" and delivery will be necessary. While the patient is making her decision, I usually will begin indomethacin 50-100 mg initial dose followed by 25-50 mg every 6 hours and an antibiotic cocktail of a cephalosporin (or ‘penicillin’), azithromycin, and metronidazole administered intravenously. Most patients will opt for cerclage under these circumstances simply because they feel like “what have I got to lose” if the chances for the baby are otherwise hopeless.
The decisions are a little tougher when the baby is in the range of potential viability, especially from 23 weeks on. As in most neonatal intensive care units with high volume services, our neonatal survival rate between 23 and 24 weeks is in the range of 30-50% and it goes up dramatically from that point on, although at the earlier gestational ages, there is also a very high risk of long-term morbidity and mortality secondary to complications of prematurity. Patients at these gestational ages are evaluated and begun on the same treatment regimen I have detailed above with the addition of corticosteroids to accelerate fetal lung maturation. Usually we provide consultation with one of the neonataologists as well.
Under these circumstances, if the membranes are above or at the external cervical os, I still offer cerclage as an option – although the risks are clearly delineated that we could precipitate a delivery as a result of the procedure itself at a time in pregnancy when even days can have a significant impact on potential outcome for the baby. If the membranes have completely prolapsed into the vagina, the success of the procedure is so low with the risk of rupturing membranes during the procedure and the risk of subsequent infection following the procedure so high, that I will usually advise only conservative management with bedrest, antibiotics, corticosteroids, and tocolytic therapy in the hospital until delivery.
Although many years ago, before the dramatic advances in neonatal intensive care, I would perform cerclages if appropriate up to 30 weeks gestation, it is difficult to justify that now – indeed, I have to think long and hard before even offering it as a possibility once a pregnancy has reached 26 weeks. In our next post, I will detail the technique I have used for cerclage placement in these situations for the better part of 20 years…