Observations on the origin of amniotic fluid enzymes

Amniotic fluid concentrations of secreted pregnancy-associated endometrial alpha 1- and alpha 2-globulins (alpha 1- and alpha 2-PEG)

The levels of pregnancy-associated endometrial alpha 1- and alpha 2-globulins (alpha 1- and alpha 2-PEG), the two major proteins synthesized and secreted by the endometrium in vitro, have been assayed in 210 amniotic fluid specimens obtained at termination of pregnancy or by amniocentesis, or at delivery. alpha 1-PEG was undetectable until week 10 and thereafter rose to peak levels between weeks 20 and 24. Levels fell 15-fold by week 35 but substantial amounts were still present at parturition. alpha 2-PEG was present at highest levels during early pregnancy, at weeks 6-15, but thereafter levels rapidly fell until during weeks 31-42 alpha 2-PEG was detectable in only 3 of 25 specimens. During weeks 15-20, when alpha 2-PEG levels fell and alpha 1-PEG levels rose, a high correlation was observed between the week of gestation and the log of the ratios of the concentration of these proteins. These observations provide the opportunity to assess the role of endometrial and decidual dysfunction in the aetiology of pregnancy disorders.

Alkaline phosphatase activity in amniotic fluid in pregnancies with fetal disorders

Alkaline phosphatase (ALP) activity was determined in 255 amniotic fluid samples collected by amniocentesis between 15 and 39 weeks of gestation. The samples were originally used for chromosomal analysis and/or alpha-fetoprotein measurements. The mean ALP activity in early amniotic fluid from pregnancies with fetal trisomy 18 and 21 syndromes was half of that found in the controls. Highly elevated ALP activity (over 10 times the median level) was found in 14 samples. Two of these pregnancies had normal outcome. Three samples were from pregnancies with intrauterine fetal death. Fetal disorders, including abdominal wall defect (four cases), Meckel's syndrome (two), hydrops fetalis syndrome (two) and genital anomaly (one), were observed in nine cases. Moderately elevated ALP activity (over three times the median) was found in 10 cases, including five pregnancies with a preterm labour shortly after the sample collection. The results indicate that elevated ALP activity in the third trimester amniotic fluid is often associated with fetal disorders.