PP122. Lack of correlation between placental weight and circulating soluble fms-like tyrosine kinase-1 and placental growth factor suggests trophoblastic activity as a major contributor to the serum pool

Introduction Serum levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) are altered in preeclampsia and fetal growth restriction. Whether the alterations result from mere variation in trophoblastic mass or trophoblastic activity in these diseases is still elusive. Objectives Using placental weight as a surrogate for trophoblastic mass, we explored the relationship between placental weight at delivery and serum levels of sFlt-1 and PlGF at various gestational ages in normotensive pregnant Thai women. Methods One hundred and forty two serum samples from healthy, normotensive, singleton Thai pregnant women were prospectively collected from 6 gestational age intervals; 10–14, 15–19, 20–24, 25–29, 30–34, and 35–40 weeks’. Analysis for the levels of sFlt-1 and PlGF was made from fresh specimens, using a commercially available automated system. Placental weight at delivery was followed in participants who remained unaffected with preeclampsia or fetal growth restriction until the time of delivery. Results Statistical analyses were achieved from 140 participants. Quartiles for these markers were calculated for each gestational age interval. Serum sFlt-1 levels continuously increased through the pregnancy. Serum PlGF levels reached its peak levels at menstrual period of 25–29 weeks’, and then declined. Serum sFlt-1/PlGF ratios were consistently lower than that of the European population throughout the pregnancy. No significant correlation is found between placental weight at delivery, and serum levels of either sFlt-1 or PlGF at any gestational age interval. Conclusion Ethnic variation of serum angiogenic markers is shown in this study. Lack of correlation between placental weight and serum angiogenic markers in normotensive individuals suggest that trophoblastic activity, and not number of the trophoblast, contribute to the alterations in circulating pool. This may facilitate a better understanding for its potential clinical applications of these biomarkers for other placental related diseases.