Proton magnetic resonance spectroscopy of human amniotic fluids sampled at 17-18 weeks of pregnancy in cases of decreased digestive enzyme activities and detected cystic fibrosis.

Low digestive enzyme activities in human amniotic fluid can be observed in normal and disease-affected pregnancies: cystic fibrosis, trisomy 21, intestinal atresia. Amniotic fluids were analyzed by proton nuclear magnetic resonance (NMR) spectroscopy in order to specify prenatally the etiology of low digestive enzyme activities observed at 17-18 weeks of amenorrhea. A total of 114 amniotic fluid samples were collected at 17-18 weeks of amenorrhea. Karyotyping and assays of digestive enzyme activities were performed in all cases. Samples were divided into six groups according to enzyme activities and pathology. Proton spectra were retrospectively recorded. Many compounds, such as amino acids and carboxylic acids, were detected by NMR. The same resonance intensities (normalized to creatinine) were observed in the six groups. Nevertheless, an unidentified resonance at 1.05 ppm was detected in seven out of 13 cases of cystic fibrosis affected fetuses. The NMR spectra demonstrated the stability of the amniotic fluid composition at 17-18 weeks of amenorrhea, even when the fetus was affected by a disease such as trisomy 21 or intestinal atresia. The resonance associated with most cases of cystic fibrosis should be further investigated.