Pattern of serum total alkaline phosphatase activity in different stages of normal third trimester pregnancy in Zaria, Northern Nigeria

Background: There are reports from many parts of the world on the increased activity of serum total alkaline phosphatase (TALP) in pregnant women, especially during the last half of pregnancy. There is no such documented finding in this environment. There is the need to determine the serum TALP activity in different stages of normal 3 rd trimester pregnancy in Zaria to allow for proper interpretation of this analyte at this stage of pregnancy. Subjects and Methods: A cross sectional descriptive study carried out among 100 healthy pregnant women in their 3 rd trimester. They were randomly selected from the antenatal clinic of Ahmadu Bello University Teaching Hospital, Zaria. Serum TALP activity was measured using the 4-Nitrophenylphosphate (4-NPP) method. Socio-demographic and obstetrics characteristics were obtained using an administered questionnaire. Microsoft Excel (Microsoft office, 2003) was used for data analysis. Distributions of ALP activities were found to be skewed; hence, non-parametric analyses using percentiles were used in measuring the variation. A P-value of equal to or less than 0.05 (P ≤ 0.05) was considered as statistically significant. Results: The serum TALP activity in normal 3 rd trimester pregnancy was found to be higher when compared to the normal population, with a gradual increase with advancing gestational age. Subjects in the gestational age group of 28 to 30 weeks had a serum TALP activity of 46-138 IU/L, with a continuous increase of up to 213 IU/L at 39 weeks of gestation. A sudden drop in activity was observed at the gestational age of 40 weeks and above. The overall serum TALP activity in normal 3 rd trimester pregnancy was found to be 41-206 IU/L. Conclusion: A higher serum TALP activity for normal 3 rd trimester pregnancy was confirmed for this environment, as has been found elsewhere. There is the need to interpret serum TALP activity in pregnancy with caution.