Fetal foot length at delivery as a tool for determining gestation length in non-macerated stillbirths

Abstract

Objective: To assess whether fetal foot length at autopsy could reliably indicate gestation duration at stillbirth and the effects of maceration on this method.

Methods: The present cross-sectional secondary analysis was part of the Safe Passage Study; all Safe Passage Study participants who experienced a stillbirth at Tygerberg Academic Hospital, Cape Town, South Africa, between August 1, 2007, and January 31, 2015, were eligible to participate. After providing written informed consent for autopsy, the duration of gestation calculated using early ultrasonography and fetal foot length were compared.

Results: There were 69 fetal autopsies included in the present study; placental histology was available for 65. Generally, the gestation length calculated from the first ultrasonography scan correlated well with that calculated from the fetal foot length (Spearman correlation=0.85). However, significant differences were found in the gestation lengths calculated when the fetus was macerated (P<0.001), or when umbilical cord pathology (P<0.001) or maternal vascular malperfusion (P<0.001) was the cause of fetal death.

Conclusion: Foot length at stillbirth was a good indicator of gestation length; however, it was a weaker indicator if fetal maceration had occurred.

Keywords: Fetal growth; Foot length; Gestational age; Macerated stillbirth; Maternal vascular malperfusion; Umbilical cord pathology.

Figure 1

Correlation between the lengths of gestation at delivery calculated from ultrasonography data and using fetal foot length. Spearman correlation 0.85; P<0.001. Intra-class correlation for agreement 0.836 (95% CI 0.556–0.924); intra-class correlation for consistency 0.885 (95% CI 0.820–0.927). The solid line denotes the regression line and the broken line denotes the y=x line. Abbreviation: CI, confidence interval.

Figure 2

Effect of maceration on the difference in gestation length calculated using either ultrasonography data or fetal foot length. Significant differences in the calculated gestation were recorded if there was mild (19 days) or severe maceration (34 days); current effect F(2, 66) 17.154; P<0.001. Whiskers denote 95% confidence intervals and duplicated letters above whiskers indicate an absence of a significant difference.

Figure 3

Effect of different causes of stillbirth on the difference in gestation length calculated using either ultrasonography data or fetal foot length. Significant differences were recorded for UP (P<0.001), Cord (P<0.001), and other (P=0.026) causes of fetal death. Whiskers denote 95% confidence intervals and duplicated letters above whiskers indicate an absence of a significant difference. Abbreviations: UP, maternal vascular malperfusion; Cord, cord pathology; I, infection; AB, placental abruption; Cong ab, congenital anomalies.