When there is a threatened delivery in the periviable period, one of the decisions that have to be made is about the mode of delivery. In my opinion (IMHO, I think those young'uns say) we should consider the different parts of the decision-making to be linked but separate. A decision to give antenatal steroids, for example, does not mandate a cesarean delivery or intensive care of the baby. A decision to not perform a cesarean does not mean that fetal heart rate monitoring should not be performed, or that a live-born baby might not have active resuscitation.
One might decide, for example, that a mother will receive betamethasone, with a goal of improving the chances of a good outcome, and we might then decide to plan on providing active intensive care for the baby, but then the decision may be that the risks and benefits, for this particular mother, of performing a cesarean are not consistent with her goals and values; in which case a cesarean for fetal indications will not be performed. We might still want to monitor the fetal heart rate, as knowledge of the heart rate during the last minutes prior to delivery could help in resuscitation decisions; if the fetus has been bradycardic for a prolonged period prior to delivery, and is then born asystolic, a decision to not attempt resuscitation could be quite reasonable, compared to a fetus with good heart rate patterns just before delivery.
One part of this decision-making matrix that has been somewhat lacking is good data about maternal complication rates in this time period. What are the risks to the mother of a classical cesarean, a lower segment cesarean, or a vaginal delivery before 26 weeks? What are the risks for this pregnancy, and for the next pregnancy?
Several recent articles, one still on-line only, help to clarify the risks (although the relative benefits of each mode of delivery need RCTs for reliable scientific data, which may well never be done).
These articles are all therefore observational studies, which describe the frequency of various maternal outcomes after preterm delivery.
The first article answers a question for which I last did a literature search a couple of years ago, at that time I wasn't able to find any good data, : "what is the risk of a classical, or an extremely preterm lower transverse, cesarean on uterine rupture in future pregnancies?" This risk is often stated by obstetricians to be a major part of their reluctance to perform a cesarean in the periviable period, and although the risks are clearly greater than for a vaginal delivery I was never sure what was the magnitude of that risk. In this publication the authors state that they also could find no good data, so my lit review was not inadequate, there just was no data. Their study, in contrast, gives very clear information about those risks.
The authors used linked databases from Washington state to determine the risks of uterine rupture in a subsequent pregnancy after a cesarean delivery performed at 20-26 weeks gestation, and compared the risks to a cesarean performed at term.
Overall, the risks of future uterine rupture after a periviable cesarean were about 1.8% (2.4% if you restrict the analysis to classical scars) compared to 0.4% after a cesarean at term. The results are also presented as an Odds Ratio (which is 4.9, 95% CI 1.7-13.1); unfortunately few physicians understand what an Odds Ratio is (but when the risks are small there isn't much difference between the Odds Ratio and the Relative Risk). I think for individual mothers making a decision, that the absolute risks are more useful numbers; also a comparison to cesarean deliveries performed at term is an interesting and useful comparison to put the risks in context, but doesn't help in decision-making much as that isn't the option that would be on the table.
There is also a comparison of other maternal morbidities in the current (or "index") pregnancy; periviable cesarean deliveries are a little more morbid (14% of mothers have one or more of transfusion, bleeding, coagulopathy, chorioamnionitis, sepsis, maternal infection or hysterectomy as recorded in the hospital discharge diagnoses, which means that bleeding is not strictly defined) than term cesareans, which I was a bit surprised to see were also pretty morbid (10% had the same complications) but the difference was consistent with a chance finding.
Mothers who have a periviable cesarean are different in many ways from mothers having a term cesarean, so how much of the increase in maternal morbidity is due to the classical incision (almost all of the term cesareans are lower segment transverse incisions) and how much to their other demographic and clinical differences? Also important, does having a cesarean delivery at periviable gestation have other effects on subsequent pregnancies, other than the risk of uterine rupture?
The same group (Lannon S, et al. Mode of delivery at periviable gestational ages: impact on subsequent reproductive outcomes. Journal of perinatal medicine 2013. p. 691.)
has looked at the risks for a subsequent pregnancy, and compared a vaginal birth in the periviable period to a cesarean delivery. Overall having a delivery in the periviable period led to the same outcomes in a subsequent pregnancy regardless of mode of delivery, the gestational age at birth of the subsequent pregnancy were almost identical; the only individual outcome which was affected was uterine rupture. There were some very small differences, which were statistically significant because of the large numbers of pregnancies being evaluated, for example after a periviable vaginal delivery the median gestational age of the subsequent pregnancy was 38 weeks, and after a cesarean it was 37 weeks. the authors interpret this difference as the wish to perform cesarean in the subsequent pregnancy prior to labour to avoid uterine rupture if possible.
The next study compared the maternal outcomes of classical cesarean to low transverse cesarean on maternal morbidity (for the index pregnancy only). Kawakita T, et al. Maternal Outcomes associated with early preterm cesarean delivery. Am J Obstet Gynecol. 2016. They looked at hospital records of mothers who delivered between 23 and 32 weeks gestation, and then looked at the stratum under 28 weeks. They showed that in the higher gestational age stratum (28 to 32 weeks) that classical cesareans had more morbidity, in particular more transfusion and more need for ICU admission. But in the lower GA group the risks were the same for both types of cesarean incision, for example about 10% needed a blood transfusion in each group.
Another paper from the NIH MFM network examined deliveries between 23 weeks and 34 weeks. Reddy UM, et al. Serious maternal complications after early preterm delivery (24-33 weeks' gestation). Am J Obstet Gynecol. 2015;213(4):538 e1-9. Deliveries at 23 to 27 weeks gestation were more morbid, with 7% having hemorrhage, compared to 3% for the group at 31 to 33 weeks, in this study hemorrhage was clearly defined, as it was part of the prospective data collection, as blood loss ≥1500 mL, blood transfusion, or hysterectomy for hemorrhage.
The absolute risks associated with an extremely preterm cesarean delivery are not noted in this publication, but the adjusted relative risk of a cesarean delivery at 23 to 27 weeks compared to a vaginal delivery is presented. The combined relative risk of hemorrhage, postpartum infection, and ICU admission is 3.22 for a classical cesarean delivery and it is 2.8 for a low segment delivery, both compared to vaginal delivery at the same gestational age.
I can't tell you based on these data what are the absolute risks, but I guess-timate from these data (about half of the deliveries were vaginal) that about 6% of mothers delivering vaginally between 23 and 27 weeks will have a serious complication, (hemorrhage infection or ICU) and about 18% of mothers who had a cesarean in this time interval. That is a bit higher than Kawakita if I have estimated the absolute risks correctly, but not too much different, and of course definitions and data finding are different.
Another study from the Canadian Perinatal Network (Crane J, et al. Maternal and Perinatal Outcomes of Pregnancies Delivered at 23 Weeks’ Gestation. JOGC 2015;37(3):214-24.) included only deliveries at 23 weeks, serious maternal outcomes were common (about 40% of mothers had at least one serious outcome), but the large majority of them were chorioamnionitis, about 38%; after that the next most common was blood transfusion which was required in about 4% of women. About 10% of the 230-ish mothers had a cesarean, and the authors don't compare the maternal outcomes between Cesarean and vaginal deliveries, but most of the data are from the vaginal deliveries.
To summarize, having babies is dangerous. Having a baby by cesarean section at term has risks, including a frequent need for transfusion. The overall risks of having a cesarean delivery in the periviable period for the current pregnancy are somewhat greater than at term, but the magnitude of the increase is probably less than 5%, most of those risks are short-term and treatable, with the most common being the need for a transfusion. A vaginal delivery in the periviable period has fewer risks for the mother Uterine rupture in the next pregnancy, if there is one, occurs less than 3% of the time.
I want to emphasize here that uterine rupture is a big deal. I am not trying to minimize it, and we should find a way to explain to mothers the importance of uterine rupture in future pregnancies, but we should do that without exaggerating its incidence (perhaps a visual decision aid?), and ensuring that mothers understand the major impact of a uterine rupture, and that the risk of rupture persists even when the obstetrician tries to take steps to avoid it. Of course that is a risk which is important for a woman who will have a future pregnancy, and may be of little importance for a woman who has decided against that option.
I think that it is good for the neonatal team to have an understanding of the risks to the mother, so that we can be reasonable and well-informed as we participate in decision-making; but clearly the final decision about route of delivery should be made between the mother and her obstetrician.