The American College of Obstetricians and Gynecologists and the Society for Maternal–Fetal Medicine have long discouraged nonindicated delivery before 39 weeks of gestation. The reason for this longstanding principle is that the neonatal risks of late-preterm (34 0/7–36 6/7 weeks of gestation) and early-term (37 0/7–38 6/7 weeks of gestation) births are well established. However, there are a number of maternal, fetal, and placental complications in which either a late-preterm or early-term delivery is warranted. The timing of delivery in such cases must balance the maternal and newborn risks of late-preterm and early-term delivery with the risks of further continuation of pregnancy. Recently, the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the Society for Maternal–Fetal Medicine convened a workshop to address this issue by summarizing the available evidence and making recommendations (1). The evidence regarding timing of indicated delivery for most conditions is limited; therefore, these recommendations are based largely on expert consensus and relevant observational studies, and management should be individualized.
There are several important principles to consider in the timing of delivery. First, the decision making regarding timing of delivery is complex and must take into account relative maternal and newborn risks, practice environment, and patient preferences. Second, late-preterm or early-term deliveries may be warranted for either maternal or newborn benefit or both. In some cases, health care providers will need to weigh competing risks and benefits for mother and newborn; therefore, decisions regarding timing of delivery must be individualized. Additionally, recommendations such as these are dependent on accurate determination of gestational age.
Amniocentesis for the determination of fetal lung maturity in well-dated pregnancies generally should not be used to guide the timing of delivery. The reasons for this are multiple and interrelated. First, if there is a clear indication for a late-preterm or early-term delivery for either maternal or newborn benefit then delivery should occur regardless of such maturity testing. Conversely, if delivery could be safely delayed in the context of an immature lung profile result then no clear indication for a late-preterm or early-term delivery actually exists. Second, mature amniotic fluid indices are not necessarily reflective of maturity in organ systems other than the lungs.
Table 1 presents recommendations for the timing of delivery for a number of specific conditions. This list is not meant to be all-inclusive, but rather a compilation of indications commonly encountered in clinical practice. “General timing” describes the concept of whether a condition is appropriately managed with either a late-preterm or early-term delivery. “Suggested specific timing” refers to a more defined timing of delivery within the broader categories of late-preterm or early-term delivery. These are recommendations only and will need to be individualized and re-evaluated as new evidence becomes available.
1. Spong CY, Mercer BM, D’Alton M, Kilpatrick S, Blackwell S, Saade G. Timing of indicated late-preterm and early-term birth. Obstet Gynecol 2011;118:323–33.