BACKGROUND. There is little published work on the risk of stillbirth across pregnancy for small-for-gestational-age (SGA) and large-forgestational
(LGA) pregnancies in low-resource settings.
OBJECTIVES. To compare stillbirth risk across pregnancy between SGA and appropriate-for-gestational-age (AGA) pregnancies in Western
Cape Province, South Africa (SA).
METHODS. A retrospective audit of perinatal mortality data using data from the SA Perinatal Problem Identification Program was conducted.
All audited stillbirths with information on size for gestational age (N=677) in the Western Cape between October 2013 and August 2015
were included in the study. The Western Cape has antenatal care (ANC) appointments at booking and at 20, 26, 32, 34, 36, 38 and 41 (if
required) weeks’ gestation. A fetuses-at-risk approach was adopted to examine stillbirth risk (28 - 42 weeks’ gestation, ≥1 000 g) across
gestation by size for gestational age (SGA <10th centile Theron growth curves, LGA >90th centile). Stillbirth risk was compared between
SGA/LGA and AGA pregnancies.
RESULTS. SGA pregnancies were at an increased risk of stillbirth compared with AGA pregnancies between 30 and 40 weeks’ gestation, with
the relative risk (RR) ranging from 3.5 (95% confidence interval (CI) 1.6 - 7.6) at 30 weeks’ gestation to 15.3 (95% CI 8.8 - 26.4) at 33 weeks’
gestation (p<0.001). The risk for LGA babies increased by at least 3.5-fold in the later stages of pregnancy (from 37 weeks) (p<0.001). At
38 weeks, the greatest increased risk was seen for LGA pregnancies (RR 6.6, 95% CI 3.1 - 14.2; p<0.001).
CONCLUSIONS. There is an increased risk of stillbirth for SGA pregnancies, specifically between 33 and 40 weeks’ gestation, despite fortnightly
ANC visits during this time. LGA pregnancies are at an increased risk of stillbirth after 37 weeks’ gestation. This high-risk period highlights
potential issues with the detection of fetuses at risk of stillbirth even when ANC is frequent.