[Nitrogen and oxygen levels in placenta - a predictor for retinopathy of prematurity]

To study the distribution of chemical elements in the placenta of pregnant women at 24-35 and 39-40 weeks of gestation, and to assess the possibility of using data on the levels of principle chemicals for predicting clinical manifestation of retinopathy of prematurity (ROP).

The study examined 375 placenta tissue fragments of pregnant women for levels of the following chemical elements: carbon (C), nitrogen (N), oxygen (O), calcium (Ca), chlorine (Cl), potassium (K), sodium (Na) and phosphorus (P). Subjects were divided into 3 groups: 1st group consisted of 41 pregnant females (205 fragments of placenta tissue) at weeks 24-35 of gestation, whose children would not develop ROP; 2nd group included 14 mothers (70 fragments of placenta tissue) at weeks 39-40 of gestation; 3rd group - 20 pregnant (100 fragments of placenta tissue) at weeks 24-35 of gestation, whose children would be diagnosed with ROP. Examination of the eye fundi of children from ROP risk group was done by digital retinoscopy and indirect binocular ophthalmoscopy. Chemical composition of placenta was studied using energy-dispersive x-ray microanalysis based on scanning electron microscopy.

Descriptive statistical values of chemical elements were obtained for the three study groups. Statistically significant percentile differences were detected in the levels of C, N and O in the samples (p<2.2·10-16). Differences in the levels of N, O, K, and Na in the placenta of pregnant women of the three study groups were determined.

Comparative chemical analysis of the placentas of pregnant women at different gestation periods showed higher levels of N, K, Na, and lower levels of O in the group of mothers whose children would be diagnosed with ROP. Normalized nitrogen content in the placenta of women whose children would develop ROP was 12.9%. Thus, nitrogen content may serve as a pre-clinical marker of retinopathy of prematurity.