Clinical and biochemical aspects of pregnancy-induced hypertension.

In order to study what characteristics accompany the development of pregnancy-induced hypertension (PIH) and what parameters, if any, differentiate hypertension alone from hypertension with proteinuria, we evaluated 119 women with PIH who had hypertension alone, 73 women with PIH who had hypertension and proteinuria greater than or equal to 0.3 g/l, 63 women with normal pregnancy, 20 normal non-pregnant women. In comparison with normal pregnant women and normal non-pregnant women, women with PIH showed an increase in heart rate, suggesting an increased peripheral sympathetic tone, and an initial derangement in renal function as shown by the increase in serum uric acid and reduction in sodium excretion and total and fractional calcium excretion at any given level of sodium excretion. These changes were more marked in patients with hypertension and proteinuria. Higher levels of systolic blood pressure (SBP) were present in women with hypertension alone who subsequently developed proteinuria, compared with those who had only hypertension until term. According to our data hypertension alone and hypertension with proteinuria seem to be two aspects of only differing severity of the same disease.

Plasma concentrations of atrial natriuretic factor and hemodynamics in pregnancy-induced hypertension.

Plasma values of atrial natriuretic factor (ANF) were evaluated in 31 women with pregnancy-induced hypertension (PIH) and 31 normal pregnant women at the same age of gestation. In 27 women with PIH and 27 normal pregnant women forearm venous tone (FVT) was evaluated by Strain Gauge Plethysmography. Forearm vascular resistance (FVR) was measured as the ratio of mean blood pressure (MBP) to forearm blood flow. In addition Cardiac Index (CI) by means of transthoracic electrical bioimpedance and total peripheral vascular resistance (TPR) (with the Frank Equation) were also measured. In comparison with the normal pregnant women, the women with PIH had similar values of hematocrit (as an index of plasma volume) and significantly higher levels of FVR and TPR, while ANF plasma values did not differ significantly. Subdividing the women with PIH in relation to the presence of proteinuria (greater than or equal to 0.3 g/l), those with proteinuria, in addition to significantly higher levels of FVR and TPR, had significantly higher levels of FVT than normal pregnant women, while ANF plasma values were higher even though the difference was only near the level of significance. Hypertensive women with proteinuria also had higher values of FVT than hypertensive women without proteinuria. By means of multiple regression ANF did not show any significant correlations with hematocrit or sodium excretion. Hypertension with proteinuria seems to represent a more severe form of the disease in which, in addition to the probable influence of other factors such as the renin-angiotensin and prostaglandin systems, a greater increase in peripheral sympathetic tone than in hypertension alone appears to be present, causing a reduction in venous compliance in addition to the elevation in FVR and TPR, with increase in central blood volume and atrial stretch. This may explain the higher ANF plasma levels in these patients in comparison with normal pregnant women, even though the absence of a significant correlation of ANF with hematocrit and the fact that ANF increase was only near the level of significance may suggest a change in the relation between ANF secretion and atrial volume receptors in pregnancy either normal or complicated by hypertension. ANF does not seem to play an important role in water and sodium excretion in PIH probably because of the presence of very high plasma levels of hormones such as aldosterone, progesterone and oestriol which, together with renal prostaglandins, seem to be involved in diuresis and natriuresis in pregnancy.

Maternal and fetal prolactin in pregnancy-induced hypertension.

In plasma from 35 women with pregnancy-induced hypertension (PIH) and 35 normal pregnant women both at 39 weeks of gestation, plasma prolactin levels were measured at 8.30 a.m. (PRL1) and 9.30 a.m. (PRL2) under basal conditions. At delivery umbilical cord blood samples were taken for measurement of fetal prolactin (PRLF). PRL1 and PRL2 were higher in women with PIH, but no significant relations were found between PRL1/PRL2 and blood pressure. PRLF did not differ when infants of mothers with PIH and infants of normal pregnant women were compared, but PRLF had a significant direct independent relation with PRL2. The latter relation may be due to the increase in placental oestrogens during pregnancy, which stimulate both the maternal and fetal hypophyses and their prolactin secretion. PRLF did not show any relation with neonatal morbidity, but PRL1 showed a significant direct relation with the Apgar score at 5 min.

Plasma concentrations of atrial natriuretic factor in normal pregnancy and early puerperium.

The atrial natriuretic factor (ANF) and parameters related to renal sodium handling and renal function were evaluated in 92 normotensive pregnant women at different gestational ages (1st group: 7th-13th week, 2nd group: 14th-20th week; 3rd group: 21st-27th week; 4th group: 28th-34th week; 5th group: greater than 34th week), in 15 normotensive non-pregnant women and in 15 normotensive women 6 days after spontaneous delivery at the end of a normal pregnancy. ANF did not differ significantly between the 5 groups of pregnant women while, concurrently with a further increase in plasma volume (as shown by our data) it was significantly higher in late pregnancy (3rd and 5th groups) than in the non-pregnant women. ANF in post-partum women was significantly higher than in non-pregnant and pregnant women. Only in post-partum women was ANF significantly directly related to sodium excretion. Even though ANF does not seem to play an important role in water and sodium excretion in pregnancy in comparison with other hormones such as progesterone, oestriol and aldosterone, the higher levels of ANF in late pregnancy probably represent a compensatory increase when a given threshold of plasma volume (and therefore of atrial stretch) is reached. However ANF does seem to play a more important role in the induction of diuresis and natriuresis in early puerperium.

Role of prolactin in pregnancy hypertension.

In 51 patients with pregnancy hypertension (H) and 51 normotensive gravid women (N), matched for age of gestation, plasma prolactin was measured at 8.30 am (PRL1) and 9.30 am (PRL2) in basal conditions and after 10 minutes of upright posture (PRL3). While in N there was a fall from PRL1 to PRL2 which was nonsignificant, in H there was a significant fall from PRL1 to PRL2. With upright posture there was a further decrease in prolactin in N and a significant increase in H. With multiple regression analysis, systolic and diastolic blood pressure did not show any independent relations with PRL1, PRL2 and PRL3, while serum proteins and proteinuria showed a significant relation with PRL1, as did serum proteins, serum potassium and serum urate with PRL2 and serum urate with PRL3. As has been suggested in primary hypertension, a certain increase in peripheral sympathetic tone, dependent on a decreased central dopaminergic activity, may be present in patients who develop pregnancy hypertension compared to normotensive pregnant controls and may be involved in the pathogenesis of pregnancy hypertension.