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The Development of Pre-Eclampsia and Reverse Endodiastolic Flow

The Development of Pre-Eclampsia and Reverse Endodiastolic Flow

Pre-eclampsia and intrauterine growth restriction is associated with an inadequate quality and quantity of the maternal vascular response to placentation. In both conditions, there are characteristic pathological findings in the placental bed. Brosens et al. examined placental bed biopsies from pregnancies complicated by pre-eclampsia and reported absence of physiological changes in the spiral arteries beyond the decidual- myometrial junction in more than 80% of the cases.

Robertson et al. examined placental bed biopsies from hypertensive women and found a difference between the lesions seen in women with pre-eclampsia and those with essential hypertension. In pre-eclampsia, there was a necrotizing lesion with foam cells in the wall of the basal and spiral arteries, which was referred to as 'acute atherosis'. In essential hypertension, there were hyperplastic lesions in the basal and spiral arteries.

Sheppard and Bonnar reported that, in pregnancies with intrauterine growth restriction (irrespective of whether there is coexistent pre-eclampsia or not), there are atheromatous-like lesions that completely or partially occlude the spiral arteries; these changes are not present in pregnancies with pre-eclampsia in the absence of intrauterine growth restriction. In contrast, Brosens et al. reported lack of physiological changes in all cases of pre-eclampsia, irrespective of the birth weight, and in most cases of intrauterine growth restriction; however, acute atherosis was found only in pre-eclampsia. Khong et al. reviewed some of the archived biopsies of Brosens et al.

They assessed the proportion of spiral arteries converted to uteroplacental arteries. In all cases of pre-eclampsia and in two-thirds of those with intrauterine growth restriction (defined as birth weight < 10th centile), there was no evidence of physiological change in the myometrial segments. Furthermore, complete absence of physiological change throughout the entire length of some spiral arteries was seen in approximately half the cases of pre-eclampsia and intrauterine growth restriction.

Nicolaides et al. measured blood gases in umbilical cord blood samples obtained by cordocentesis in growth-restricted foetuses. End-diastolic frequencies were absent in 22 cases; 80% of these foetuses were found to be hypoxemic and 46% also acidemic. In contrast, only 12% of the foetuses with positive end-diastolic frequencies were hypoxemic and none was acidemic. In a multicentre study involving high-risk pregnancies, the patients were subdivided into three groups depending on the flow velocity waveforms in the umbilical artery (positive end-diastolic frequencies, n = 214; absent end-diastolic frequencies, n = 178); and reversed end-diastolic frequencies, n = 67). The overall prenatal mortality rate was 28% and the relative risk was 1.0 for patients with present frequencies, 4.0 for those with absent frequencies and 10.6 for those with reversed frequencies. Significantly more neonates in the groups with absent or reversed frequencies needed admittance to the neonatal intensive care unit and they had a higher risk of cerebral haemorrhage, anaemia or hypoglycaemia. In addition to increased fetal and neonatal mortality, growth restriction with absent or reversed end-diastolic frequencies in the umbilical artery is associated with increased incidence of long-term permanent neurological damage(Breier, ...