Restriction of placental vasculature in a non-human primate: a unique model to study placental plasticity.

The limits of placental plasticity, i.e., the ability of the placenta to adapt and alter its growth trajectory in response to altered fetal requirements, are not known. We report fetal and placental hemodynamic adaptations in a novel non-human primate model in which the fetal inter-placental bridging vessels were surgically ligated. Doppler ultrasound studies showed that the rhesus placenta compensates for an approximate 40% reduction in functional capacity by increased growth and maintenance of umbilical volume blood flow. This unique experimental animal model has applications for mechanistic studies of placental plasticity and the impact on fetal development.

Changes in maternal heart dimensions and plasma atrial natriuretic peptide levels in the early puerperium of normal and pre-eclamptic pregnancies.

OBJECTIVE: To measure plasma atrial natriuretic peptide (ANP) in relation to maternal haemodynamics and body fluid balance in the early puerperium following uncomplicated pregnancy and pre-eclampsia. DESIGN: A longitudinal study from late pregnancy and into the early postpartum period (days 1 to 3 and days 4 to 6) compared with nonpregnant controls. SUBJECTS: Eleven women with uncomplicated pregnancies, 12 women with pre-eclampsia and 12 healthy, nonpregnant women. MAIN OUTCOME MEASURES: Maternal heart dimensions determined by M-mode echocardiography, concentrations of ANP, and daily urine output and sodium excretion. RESULTS: After delivery increases in left atrial dimensions, represented as mean (SEM), from 33.2 (1.6) to 37.7 (1.7) mm and ANP levels from 7.9 (1.1) to 19.0 (2.7) pmol/L were observed at 1-3 days postpartum in normal pregnant women, but we were not able to demonstrate a significant increase in diuresis and natriuresis. In the third trimester left atrial dimensions (38.4 (1.2) mm) and ANP levels (15.4 (2.2) pmol/L) were greater in pre-eclampsia. ANP levels rose further in pre-eclamptic women in the early puerperium (27.4 (7.4) pmol/L) with an increase in diuresis and natriuresis, while left atrial dimensions did not change significantly (39.4 (1.7) mm). A pericardial effusion was found in 11 pre-eclamptic but in only three healthy pregnant women. CONCLUSIONS: A concommitant increase in left atrial dimensions and ANP in the early puerperium following uncomplicated pregnancies is consistent with the mechanism of atrial stretch as a stimulus for ANP release, although the biological significance of this finding remained unclear. A significantly higher release of ANP in the early puerperium after pregnancies complicated by pre-eclampsia may be a mechanism which promotes the renal elimination of excessive body fluids and sodium.