Cell division in placentas of appropriate and small-for-gestational-age infants. A flow cytometry study.

Background: The purpose of this study was to examine if placentas of small- for-gestational-age (SGA) and non-SGA infants differ with respect to proliferative cell activity.

Method: Cell cycle distribution was studied in placentas from 181 SGA (birthweight < 10th percentile) and 528 non-SGA births by flow cytometry measurements of relative DNA content.

Results: The fraction of cells in various cell cycle phases (G1-, S- and G2-phases) did not differ with gestational age from 30 to 43 weeks in either of the groups. The placentas of the SGA infants had a significantly lower mean (+/-1 SEM) growth fraction than placentas of non-SGA infants (S-phase 5.2 +/- 0.2 vs 5.5 +/- 0.1, p = 0.05, and G2-fraction 5.4 +/- 0.2 vs 6.3 +/- 0.1, p < 0.001), but the overlaps of the distributions were large. Thus sensitivity, specificity and predictive values of low fractions did not differ substantially-from a purely random prediction of SGA.

Conclusions: Cell division in the placenta is maintained until and beyond term. Placentas of SGA infants have on average, lower proliferative activity than placentas of non-SGA infants, but the difference is too small to be of predictive value in identifying intrauterine growth retardation.