Extremely high levels of alkaline phosphatase and pregnancy outcome: case series and review of the literature

Objectives To evaluate the association between extremely elevated alkaline phosphatase (ALKP) levels (above 1000 U/L) and adverse perinatal outcome. Methods A retrospective case series of all parturients with extremely elevated ALKP levels taken throughout pregnancy at a single university-affiliated medical center (2010-2018). Demographics and medical data were retrieved. Following literature review, previously reported similar cases were added to the cohort. We report perinatal outcome of our cohort as well as literature review. Results During study period 11 parturients with high ALKP were identified. Ten more cases were retrieved from PubMed search. Overall, median ALKP levels were 1880 (range 1052-4488 U/L). Reasons for evaluation were mostly nonspecific symptoms (pruritus, headache, abdominal pain) or routine obstetrical evaluation. In 10/12 (83%) cases, elevated ALKP levels were of placental origin; the rest had osteal origin. Median gestational age at delivery was 38 (range 35-41); four (19%) women had preterm delivery. Six patients (29%) had gestational diabetes mellitus and six (29%) had hypertensive disorders. Histopathology of the placenta was available in eight cases: three normal histology (38%) and five with different non-specific pathologies. Conclusions We report the largest case series of extremely elevated levels of ALKP in pregnancy thus far. Our data suggest association with adverse perinatal outcome.

Keywords: adverse prenatal outcome; alkaline phosphatase; gestational diabetes; pregnancy-induced hypertension; preterm labor.