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. 2013 Oct;209(4):375.e1-7.
doi: 10.1016/j.ajog.2013.05.045. Epub 2013 May 23.

The risk of stillbirth and infant death by each additional week of expectant management stratified by maternal age

Jessica M Page  1 , Jonathan M Snowden, Yvonne W Cheng, Amy E Doss, Melissa G Rosenstein, Aaron B Caughey
Affiliations

The risk of stillbirth and infant death by each additional week of expectant management stratified by maternal age

Jessica M Page et al. Am J Obstet Gynecol. 2013 Oct.

Abstract

Objective: The objective of the study was to examine fetal/infant mortality by gestational age at term stratified by maternal age.

Study design: A retrospective cohort study was conducted using 2005 US national birth certificate data. For each week of term gestation, the risk of mortality associated with delivery was compared with composite mortality risk of expectant management. The expectant management measure included stillbirth and infant death. This expectant management risk was calculated to estimate the composite mortality risk with remaining pregnant an additional week by combining the risk of stillbirth during the additional week of pregnancy and infant death risk following delivery at the next week. Maternal age was stratified by 35 years or more compared with women younger than 35 years as well as subgroup analyses of younger than 20, 20-34, 35-39, or 40 years old or older.

Results: The fetal/infant mortality risk of expectant management is greater than the risk of infant death at 39 weeks' gestation in women 35 years old or older (15.2 vs 10.9 of 10,000, P < .05). In women younger than 35 years old, the risk of expectant management also exceeded that of infant death at 39 weeks (21.3 vs 18.8 of 10,000, P < .05). For women younger than 35 years old, the overall expectant management risk is influenced by higher infant death risk and does not rise significantly until 41 weeks compared with women 35 years old or older in which it increased at 40 weeks.

Conclusion: Risk varies by maternal age, and delivery at 39 weeks minimizes fetal/infant mortality for both groups, although the magnitude of the risk reduction is greater in older women.

Keywords: expectant management; fetal/infant mortality; infant death; maternal age; stillbirth.

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Conflict of interest statement

The authors report no conflict of interest.

Figures

FIGURE 1
FIGURE 1. Stillbirth, infant death, and expectant management risk calculations
Equation 1 shows our stillbirth risk calculation, taking into account a half-week correction to estimate the number of deliveries that have already occurred during a given week. Equation 2 demonstrates our infant death risk calculation, which includes the number of infant deaths in the numerator divided by the number of total live births during the week in question. Equation 3 describes our risk estimate for an additional week of expectant management, which combines the risk of stillbirth during the week a patient remains pregnant plus the risk of infant death following delivery at the next week. Page. Term fetal/infant mortality risk stratified by maternal age. Am J Obstet Gynecol 2013.
FIGURE 2
FIGURE 2. Composite risk of expectant management at term vs with delivery for women stratified by maternal age 35 years
The risk of infant death and composite fetal/infant mortality risk are shown by gestational age for women younger than 35 years as well as 35 years or older. Page. Term fetal/infant mortality risk stratified by maternal age. Am J Obstet Gynecol 2013.
FIGURE 3
FIGURE 3. Composite risk of expectant management at term compared with delivery for women stratified by maternal age
Four charts are shown to display the composite fetal/infant mortality risk and infant death risk in each maternal age subgroup analysis. Page. Term fetal/infant mortality risk stratified by maternal age. Am J Obstet Gynecol 2013.
See this image and copyright information in PMC

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