Objective: To determine changes in plasma C-type natriuretic peptide (CNP), a paracrine product of the vascular endothelium, in pregnancies with vascular disorders, and relate these to time of presentation and severity.
Design: Retrospective nested cases and controls.
Setting: Community study, Auckland New Zealand.
Population: Screening for Pregnancy Endpoints (SCOPE) data and bio-bank of maternal plasma.
Methods: Maternal plasma amino terminal proCNP (NTproCNP) was measured by radioimmunoassay in early (14-16 weeks of gestation, and again at 19-21 weeks of gestation) and late (34-36 weeks of gestation) pregnancy in three groups of women (20 per group): pre-eclampsia (pre-eclampsia); gestational hypertension (GHT) with small for gestational age (SGA); and uncomplicated pregnancy.
Main outcome measures: Change in NTproCNP and associations with concurrent blood pressure, time of case presentation, severity, and infant birthweight.
Results: Plasma NTproCNP in early pregnancy in women with vascular disorders did not differ from those found in controls. In late pregnancy, levels in pre-eclampsia (28.8 ± 2.3 pM) and in GHT with SGA (28.6 ± 4.8 pM) were significantly increased (P = 0.01 and 0.027, respectively) compared with controls (21.3 ± 1 pM). In pre-eclampsia, levels were significantly higher (P < 0.03) at 14-16 weeks of gestation in women diagnosed prior to 34 weeks of gestation. Combining all three groups, associations of NTproCNP with concurrent diastolic and mean arterial pressure were found at 34-36 weeks of gestation (r = 0.46). No significant associations were identified with birthweight.
Conclusions: CNP secretion during gestation is responsive to vascular stress. Plasma NTproCNP measurements may have clinical application in late pregnancy in defining the different phenotypes associated with pre-eclampsia.
Keywords: Fetal growth restriction; NTproCNP; hypertension; pre-eclampsia; pregnancy; small for gestational age.
© 2015 Royal College of Obstetricians and Gynaecologists.