Effects of pre-eclampsia and fetal growth restriction on C-type natriuretic peptide.

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.