Isolated markedly elevated maternal alkaline phosphatase in the third trimester: a potential marker of placental dysfunction and low birth weight

ABSTRACT

Background. Alkaline phosphatase (ALP) levels physiologically increase in pregnancy, primarily due to placental production. However, abnormally elevated ALP levels may be correlated with placental dysfunction and adverse birth outcomes.

Case Presentation. We report the case of a 36-year-old nulliparous woman with no significant medical history, who presented with isolated elevated ALP levels from 30 weeks of gestation, reaching a peak of 3173 U/L at 37 weeks. Other hepatic parameters and bile acids remained within normal ranges throughout pregnancy. Serial foetal growth assessments revealed a progressive reduction of percentile, with estimated foetal weight at the 12th percentile near term. Labor was induced at 39 weeks and 2 days due to foetal growth restriction. A female neonate weighing 2680 g (approximately 10th percentile) was delivered vaginally. Histopathological analysis of the placenta revealed third-trimester villous maturity with signs of hypoxic-ischemic damage and extensive intervillous fibrin deposits.

Conclusions. This case supports the hypothesis that isolated markedly elevated ALP levels in late pregnancy may be a marker of subclinical placental dysfunction and foetal growth restriction. In the absence of cholestasis or hepatic pathology, elevated ALP should prompt close foetal monitoring and placental evaluation.