Wednesday, May 28, 2008

Late prematurity rising as a result of C-sections

Tomorrow's headline today:

C- Sections a Critical Factor in Preterm Birth Increase is the title of a press release sent out by the March of Dimes today. It will undoubtedly been the subject of articles and commentary over the next fews days. It will not be surprising if lay people misunderstand the implications of the study. The press release makes it sound like prematurity, particularly late prematurity (34-36 weeks), has been rising because of C-sections that are accidentally performed too early. That's not at all what has been happening. Late prematurity has been rising as babies are delivered earlier to prevent stillbirth from underlying medical problems, and the stillbirth rate has fallen markedly in response.

The study is published in the June issue of Clinics in Perinatology. The entire issue is devoted to the epidemiology of C-sections and neonatal outcomes of C-sections. Almost all the articles in the issue are excellent, judicious and non-ideological. The article in question is The Relationship Between Cesarean Delivery and Gestational Age Among US Singleton Births by Bettegowda, et. al. The authors describe the scope of the problem:
The frequency of early cesarean delivery is increasing for medical/obstetric indications ... For many of these cases, this reflects optimal management, such as when attempting to prevent or manage fetal distress, maternal bleeding, infections, or severe preeclampsia. Given the state of available information, several important questions should be posed. First, can the increased proportion of medically complicated pregnancies explain most of the increases in cesarean section rates? Alternatively, are interventions (including cesarean sections) occurring earlier in gestation and substantially contributing to increases in preterm birth rates? Finally, if cesarean sections without medical or obstetric indications are being performed before term, can they be prevented?..
The authors review the current literature:
Ananth and colleagues also reported that more than 30% of singleton preterm births were medically indicated. In a separate study, maternal and fetal conditions requiring medical interventions that resulted in iatrogenic preterm birth were evaluated. Conditions associated with ischemic placental disease, such as preeclampsia, fetal distress, small for gestational age, and placental abruption, were implicated in more than half of medically indicated preterm births. Although this study was based on birth certificate data, other clinical studies have supported the observation that one of these four conditions was present in the majority of preterm births that required medical intervention...
Late prematurity carries risks and should not be chosen lightly. However, many babies delivered prematurely would otherwise be at substantial risk of stillbirth. As the authors point out:
The overall increase in the preterm birth rate and the concurrent increase in medically indicated preterm births have been accompanied by a decrease in stillbirth and perinatal mortality rates. Preterm-related obstetric intervention is undertaken for maternal indications and suspected fetal compromise...

Many high-risk pregnancies have benefited from obstetric intervention at 34 to 36 weeks, as suggested by declines in rates of fetal demise during the same gestational period. As such, the increase in medically indicated preterm birth might be positively viewed in light of the reduction of stillbirths and neonatal mortality... Taken together, obstetric interventions at preterm gestation to reduce risks for the mother and fetus need to be optimally balanced with risks associated with preterm birth...
Indeed, the most recent US statistics on fetal mortality show a drop of 29% in late stillbirths. So when you read the headlines tomorrow, keep in mind that the increase is late prematurity is not accidental; it is deliberate. It is an attempt to lower the stillbirth rate, and it is successfully doing so.


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