Cases We report 2 cases of isolated elevated alkaline phosphatase (ALP) in pregnancy. Two healthy primigravida who are in their twenties presented with generally feeling unwell at approximately 36-37 weeks gestations. Examination were normal. Elevated serum ALP concentration was detected (3378 - 4570 U/litre). Other laboratory tests and imaging were normal. She was followed up for one week with daily fetal monitoring using cardiotocography. Serum ALP electrophoresis showed elevated placental isozyme 1 ALP and placental isozyme 2. Deliveries were induced at 38 weeks gestations and healthy infants were delivered. The histology of the placenta was unremarkable. Serum ALP level returned to normal at 7 weeks post-partum.

Discussion ALP is an enzyme produced by liver, bones, kidneys, small intestine and placenta. In a pregnant patient, elevation of ALP may be related to HELLP syndrome, intrahepatic cholestasis, malignancy, liver or bone diseases. However, a placental origin of ALP must be explored.

ALP is physiologically produced by placenta at the brush border membranes of the syncytiotrophoblast. It appears in maternal serum in the second trimester and increases during the third trimester. Some cases of unusual elevation of placental ALP have been described. A genetic abnormality has been suspected in one case and a link with a risk of pre-term delivery has been discussed.

When a raised serum ALP concentration is present during pregnancy, differential diagnosis of other conditions must be excluded. Monitoring of fetal and maternal conditions, histopathological examination of the placenta, and postnatal follow-up of declining ALP concentrations must be performed.