Association between small-for-gestational-age at birth and placental abruption in normotensive pregnancies: a retrospective cohort study.

BACKGROUND

Hypertensive disorders in pregnancy (HDP) are well-established risk factors for placental abruption (PA). Impaired fetal growth is another candidate, yet its association with abruption in the absence of hypertension remains unverified. We used small-for-gestational-age (SGA) at birth as a pragmatic proxy to investigate whether it is independently associated with PA in normotensive pregnancies.

METHODS

A retrospective cohort study was conducted at a tertiary hospital in South China. The study population consisted of women with singleton deliveries between January 1, 2019, and December 31, 2024. Fetal growth was categorized using sex-specific percentiles of birthweight for gestational age. Birthweight < 10th percentile reflects SGA at birth. Severe SGA refers to < the 3rd percentile (P3), and those > P10 was the reference group.

RESULTS

A review of 36,544 singleton deliveries identified 654 cases of PA, of which 521 (80%) occurred in normotensive pregnancies (n = 32,269). SGA at birth was significantly associated with a higher odds of PA (2.2% vs. 1.5%, adjusted OR 1.6, 95% CI 1.21–2.16). Other associated factors for abruption included age ≥ 35 years, nulliparity, anemia, and preterm gestation. Subgroup analyses based on these factors showed that the < P3 cohort had significantly greater risk of abruption than the> P10 cohort. The corresponding relative risks (RRs) were 2.3, 1.7, 1.7, and 2.3 in the ≥ 35 years, nulliparity, anemia, and term gestation, respectively. In the comparison of the P3-P10 and the > P10 cohorts, the RRs were both 1.8 in the ≥ 35 years and term gestation. The risk between < P3 and P3–P10 was not significant in any subgroup.

CONCLUSIONS

These findings suggest that SGA at birth is independently associated with an elevated risk of PA in normotensive pregnancies, potentially explained by a shared pathophysiology of ischemic placental disease. Increased vigilance is warranted, particularly in SGA pregnancies complicated by advanced maternal age and term gestation.