The Term Breech Trial in 2000 changed the way we deliver babies. Ever since Dr. Hannah published that pivotal study, obstetricians have increasingly favored delivering breech (butt first) babies by c-section instead of vaginal delivery. By term, which is 37 weeks of pregnancy and later, only about 3 to 4% of infants are breech. However, earlier in pregnancy, many more infants haven’t had a chance to flip over to head first yet. At 26 weeks, a quarter of infants are breech, and at 32 weeks, 15% are still breech. What happens if a baby is born preterm? More of these infants are in the breech position, but we don’t have a pivotal randomized trial like the Term Breech Trial to guide us.
This month in the Green Journal, a group of researchers led by Dr. Bergenhenegouwen from the Netherlands address this very question. They weren’t able to randomize women to the type of delivery, but they were able to use data from the Netherlands Perinatal Registry, which includes data from 96% of births in the Netherlands. They studied all the preterm, singleton (no twins), breech deliveries from 2000 to 2011.
There were 8,356 preterm breech deliveries in the Netherlands from 2000 to 2011. Of all the preterm deliveries, 16% were breech. 1,935 of the pregnant mothers planned a cesarean delivery. Because the Dutch guidelines favored vaginal delivery, the majority of women planned a vaginal delivery- 6,421. Despite the best-laid plans, there is no guarantee of a vaginal delivery, and a lot of these women ended up with an emergency c-section- 2,995. Interestingly, the authors excluded a lot of women, including those with hypertension, diabetes, and preeclampsia. They also excluded fetuses with congenital abnormalities and a diagnosis of small for gestational age. Excluding these patients helps to focus the findings of the study on the mode of delivery, but it also makes the results less generalizable to the general population of women who have preterm births.
The authors wanted to know if there was a difference in the baby’s outcomes if the mother and OB team planned for a c-section or a vaginal delivery (since the planning is the only part we can control). The major outcome was death of the infant in labor or within 28 days after delivery. They also looked at complications like low Apgar scores at birth, bruising of the head, and nerve injuries, as well as serious complications like asphyxia, bleeding in the brain, brain injury, and seizures. Interestingly, if there was not enough data available in a chart review, the authors excluded the infant death from analysis. This could lead to a bias towards fewer deaths than actually occurred.
The authors found that death did not differ between the groups, except for between 28 and 31 weeks of gestation. Given that the result did not prove true for all gestational ages, this may be a false finding. However, when comparing mortality + complications for the two groups, vaginal deliveries fared worse than planned c-sections. Vaginal deliveries resulted in a 10.4% rate of death or complications and c-sections resulted in a rate of 8.7%. This was true for all gestational ages except the oldest infants- born at 32 to 36 weeks. When the authors looked only at mortality and serious complications, again the difference disappeared for all babies, except those babies born at 28 to 31 weeks. However, the planned c-section group did tend to have fewer serious complications (just not statistically significantly different). For instance, for all preterm breech deliveries, 4.1% of planned vaginal deliveries resulted in death or a serious complication and 3.2% of planned c-sections did.
The authors also looked at all the outcomes and the actual mode of delivery: planned c-section, planned vaginal delivery, and emergency c-section. They found that an emergency c-section did not reduce risk of complications and death when compared with a vaginal delivery.
Clearly, the gestational age was important. So, the authors looked at mortality over time. After 32 weeks, the chances of mortality were similar for every type of delivery.
The authors conclude that cesarean sections are associated with reduced infant deaths and complications. I would add that further research is needed, especially for gestational ages greater than 32 weeks, where the current research doesn’t show such a clear cut benefit.