Clinical syndromes with variable pathologic features

Placental histology in clinically unexpected severe fetal acidemia at term

BACKGROUND

Fetal acidemia at birth is defined as a newborn condition wherein the cord blood pH value is less than 7.0. It could represent an association with newborn brain damage; therefore, it is important to investigate which conditions precipitate its occurrence. No extensive placental analysis has been performed in cases of acidotic newborns delivered from low-risk pregnancies.

AIMS

To study placental characteristics in cases with severe fetal acidemia.

STUDY DESIGN

Retrospective case-control study.

SUBJECT

34 cases, 102 controls.

OUTCOME MEASURES

Umbilical artery pH was measured at delivery from a doubly clamped portion of the cord. Placental characteristics were compared between cases with severe fetal acidemia (cord pH at birth <7.0) and controls (normal pH at birth) in term low-risk pregnancies.

RESULTS

Macroscopic placental and umbilical cord characteristics were comparable in cases and controls whereas histological characteristics exhibited differences: diffuse villous edema, increased number of syncytial knots and villous branching abnormalities significantly affected cases more frequently than controls. Diffuse villous edema is related to fetal vascularization and associated with an increase of venous pressure; in our low-risk population, it is conceivable that these changes of fetal flow and pressure occurred in labor during the alteration of fetal heart rate. An increased number of syncytial knots and villous branching abnormalities have been previously associated with chronic placental hypoxic condition; in our low-risk population they could reflect a clinically undetectable hypoxic situation that acted during pregnancy reducing fetal resources to bear labor and delivery.

CONCLUSIONS

Placental histology provides useful information related to fetal acidemia in low-risk term pregnancy.

Diagnosing placental membrane hypoxic lesions increases the sensitivity of placental examination

CONTEXT

Two relatively unknown and recently described placental membrane hypoxic lesions (laminar necrosis and microscopic chorionic pseudocysts) have never been compared with time-honored, focal (infarction), and diffuse hypoxic lesions of placental parenchyma.

OBJECTIVE

To compare the effect on placental diagnosis of the above placental membrane hypoxic lesions and chorionic disc hypoxic lesions (infarctions and global hypoxic pattern of placental injury).

DESIGN

Twenty-three clinical (maternal and fetal) and 32 gross and microscopic placental features were retrospectively compared in 4590 placentas from a placental database built during a 13-year period: 168 placentas with at least one hypoxic disc lesion (infarct or global hypoxia) and at least one membrane lesion (microscopic chorionic pseudocysts or laminar necrosis (group 1), 750 placentas with at least one hypoxic villous lesion but no membrane lesion (group 2), 480 placentas with at least one membrane lesion but no villous lesion (group 3), and 3192 placentas with no hypoxic villous or membrane lesions (group 4).

RESULTS

Several clinical and fetal conditions and placental features known to be associated with in utero hypoxia had a statistically significant correlation with the index hypoxic placental lesions, both villous and membranous. Of placentas from patients associated with clinical conditions at risk for hypoxia, 15% featured only hypoxic membrane lesions without a chorionic disc hypoxic lesion.

CONCLUSIONS

Recognizing placental membrane hypoxic lesions increases the sensitivity of placental examination in diagnosing placental hypoxia by at least 15%. The risk of in utero hypoxia is increased when microscopic chorionic pseudocysts and laminar necrosis occur in conjunction with villous hypoxic lesions.

Acute and chronic placental membrane hypoxic lesions

Laminar necrosis (LN) and microscopic chorionic pseudocysts (MCP) are the two histological placental membrane lesions. This study retrospectively compares the clinical and placental associations of LN and MCP on a large placental material. Four hundred seventy-nine placentae featuring membrane LN (group 1), 220 placentae with MCP (group 2), and 50 placentae with both LN and MCP were identified in the database of consecutively signed by the author 4,853 placentae from 18 to 42 weeks pregnancies in years 1994-2007. Frequencies or averages of several clinical conditions and gross and microscopic placental features were compared among the groups (Yates chi-square or analysis of variance, where appropriate). Statistically significant differences were observed for preeclampsia, diabetes mellitus, stillbirths, cesarean section deliveries, placental weight, gross chorionic cysts, maternal chorioamnionitis, fetal chorioamnionitis, marginate placentae, and excessive amount of extravillous trophoblasts, respectively. Based on the above results, LN, a membrane infarction, appears to be an acute membrane hypoxic lesion, while MCP is a chronic lesion related to a more widespread extravillous trophoblasts accumulation in the placental disk. There was a substantial overlap of other clinical and placental conditions among the groups, paralleling not uncommon coexistence of acute and chronic placental hypoxia, therefore, LN and MCP, in same placentae.

Is cerebral palsy preventable?

PURPOSE OF REVIEW

To use evidence of good medical quality to update information on strategies for prevention of cerebral palsy, and on the success of these preventive efforts to date.

RECENT FINDINGS

Causes of cerebral palsy, and therefore promising approaches to prevention, differ by gestational age group and by clinical subtype. Neuroimaging and neuropathology indicate the importance of white matter disorders and of ischemic stroke in cerebral palsy; birth asphyxia, congenital malformations, placental pathology, and genetic variants also contribute to cerebral palsy risk. Multiplicity of risk factors markedly increases risk. Recent studies indicate that mild hypothermia lessens cerebral palsy risk in term infants with moderate neonatal encephalopathy, and the possibility that administration of magnesium sulphate to women in preterm labor may aid in primary prevention of cerebral palsy in very preterm infants.

SUMMARY

Past efforts to prevent cerebral palsy have not had the benefits sought, but recent results provide new hope and new challenges.