The Relationship Between Cesarean Delivery and Gestational Age Among US Singleton Births

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The increasing trend of delivering at earlier gestational ages has raised concerns of the impact on maternal and infant health. The delicate balance of the risks and benefits associated with continuing a pregnancy versus delivering early remains challenging. Among singleton live births in the United States, the proportion of preterm births increased from 9.7% to 10.7% between 1996 and 2004. The increase in singleton preterm births occurred primarily among those delivered by cesarean section, with the largest percentage increase in late preterm births. For all maternal racial/ethnic groups, singleton cesarean section rates increased for each gestational age group. Singleton cesarean section rates for non-Hispanic black women increased at a faster pace among all preterm gestational age groups compared with non-Hispanic white and Hispanic women. Further research is needed to understand the underlying reasons for the increase in cesarean section deliveries resulting in preterm birth.

Section snippets

Trends in cesarean delivery

The total cesarean section rate rose sharply in the 1970s and 1980s, accounting for only 5% of live births in 1970 and nearly 25% of all deliveries in 1988 [13], [14]. Medically indicated cesarean delivery can avert complications and adverse outcomes for the pregnant woman and fetus. However, compared with vaginal delivery cesarean section is associated with increased maternal morbidity, hospital readmission, longer hospital stays, and higher health care costs [15], [16], [17], [18], [19], [20]

Trends in preterm birth

The total preterm birth rate has increased more than 30% over the past two decades, from 9.4% of live births in 1981 to 12.7% in 2005. Between 1993 and 1996, the preterm birth rate was unchanged at 11%. In 1997, as the cesarean section rates began to increase again, the preterm birth rate increased to 11.4% and rose steadily, except for a small decrease from 11.8% to 11.6% between 1999 and 2000. Preterm birth rates differed by maternal race/ethnicity, and in 2005, non-Hispanic black infants

Changing patterns of singleton gestational age and delivery method

Analyses of the 1996 and 2004 US natality files were conducted to shed more light on the trends in cesarean section and the timing of delivery. All analyses were limited to singleton live births. Records were excluded if method of delivery, gestational age, or birth weight was unknown; if gestational age was less than 23 weeks or greater than 44 weeks; or if birth weight was less than 500 g.

Method of delivery was classified as vaginal or cesarean section. Vaginal deliveries included VBAC

Indications for cesarean deliveries associated with preterm birth

The frequency of early cesarean delivery is increasing for medical/obstetric indications and when warranted for logistic reasons, such as risk of rapid labor or distance from a hospital [8], [9], [10]. 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

Weighing the risks

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 [8], [9], [67]. Preterm-related obstetric intervention is undertaken for maternal indications and suspected fetal compromise. It has been posited that the risk tolerance and threshold for obstetric intervention has decreased with advances in neonatal and obstetric care resulting in increased preterm

Future research

Given our findings that the increase in the preterm birth rate occurred primarily among cesarean sections, it is imperative to conduct well-designed adequately powered studies that focus on the underlying reasons for the escalation in preterm birth and cesarean section rates. Additionally, estimates of the proportion of cesarean section deliveries that are not medically or obstetrically indicated need to be determined. Such clinical investigations require access to accurately reported data on

Summary

The increasing trend of delivering at earlier gestational ages has raised concerns of the impact on maternal and infant health. The delicate balance of the risks and benefits associated with continuing a pregnancy versus delivering early remains challenging. Among singleton live births in the United States, the proportion of preterm births increased from 9.7% to 10.7% between 1996 and 2004. The increase in singleton preterm births occurred primarily among those delivered by cesarean section,

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    The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the respective agencies.

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