Amniotic fluid folate level in normal pregnancy.

Folic acid level was determined in 175 amniotic fluid samples obtained by diagnostic amniocentesis from normal Thai pregnant women aged from 18 to 37 years. The mean value + one standard deviation was found to be 3.01+1.88 ng/ml, ranged from 0.5 ng/ml to 7.9 ng/ml. There were no difference of folic acid in amniotic fluid samples in different groups of gestational ages from 33 to 40 weeks and 1 to 4 gravida. The amniotic fluid folic acid also showed no correlation with the birthweight of the fetus or the foam test. The mechanism of the transfer of folic acid from mother to fetus and the significance of folic acid in the amniotic fluid is discussed in this paper.

Assessment of optical density on amniotic fluid in predicting fetal lung maturity.

The optical density (OD) of 107 amniotic fluids obtained by the amniocentesis after centrifugation at 450 x g or 2000 x g were measured at wave lengths varying from 500 to 650 nm. The OD was found to be lower at the centrifugation at 2000 x g than that at 450 x g and showed a reverse relationship to the wave lengths. In comparison with the foam test, OD measurements predicted the maturity of the fetal lung with less degree of accuracy and gave a higher false negative prediction was still relatively high. It was there fore concluded that OD measurements can not be used to replace the foam test because of their high degree of false negative prediction.

Acetylcholinesterase activity in the amniotic fluid of normal Thai pregnant women.

Acetylcholinesterase (AChE) activity was determined for 112 amniotic fluid samples obtained by amniocentesis from normal Thai pregnant women at gestational ages of 34 to 40 weeks. The method for estimation was based on inhibition the of non-specific cholinesterase (ChE) with ethoprorpazine and the expression of residual AChE activity as a percentage of total cholinesterase activity. The mean values of AChE and total ChE activities were found to be 3.65ฑ1.97 U/1 (range 1.10-7.72 U/1) and 7.61ฑ 2.55 U/1 (range 3.31-14.34 U/1) respectively. These values were in the same order of magnitude as results reported earlier in normal pregnant women. There were no relationships between gestational ages and amniotic fluid AChE, ChE or total ChE activities. As the concentration of AChE in the amniotic fluid is the index of the secreted AChE from neurons, it therefore increases considerably in fetus with open neural tube defect (NTD). The results for this pregnant women study is a base-line data for normal Thai pregnant women which will be useful in detecting the NTD in the fetus.

Acetylcholinesterase activity in cord serum and human milk.

Acetycholinesterase (AChE) and pseudocholinesterase (ChE) were determined on 44 cord serum and 72 human milk samples. The mean values of AChE were found to be 87 U/1 (rang 66-176 U/1 (range 1.1-6.6 U/1) in the cord serum and human milk respectively. There were no significant difference between the mean values of AChE in the milk samples collected on day 3 to day 12 after delivery. There was a tendency for increased AChE in the milk in the multi-gravidas more than in the first gravida. As the function of AChE in the milk is not exactly known at the neonatal gut because such systems required for the degradation of various amino acids are still not fully developed in the newborn. As AChE could not be detected in the neonatal serum aged 5 days, this indicatied that the enzyme in the milk. Cord serum contained a significantly lower ChE level than that of adult serum. As this low level rose in the first day and reached a double value within 3 weeks after delivery, this could not be due to the intake of the relatively low ChE in the human milk.