Unsupervised Placental Gene Expression Profiling Identifies Clinically Relevant Subclasses of Human Preeclampsia

Preeclampsia (PE) is a complex, hypertensive disorder of pregnancy, demonstrating considerable variability in maternal symptoms and fetal outcomes. Unfortunately, prior research has not accounted for this variability, resulting in a lack of robust biomarkers and effective treatments for PE. Here, we created a large (N=330) clinically relevant human placental microarray data set, consisting of 7 previously published studies and 157 highly annotated new samples from a single BioBank. Applying unsupervised clustering to this combined data set identified 3 clinically significant probable etiologies of PE: "maternal", with healthy placentas and term deliveries; "canonical", exhibiting expected clinical, ontological, and histopathologic features of PE; and "immunologic" with severe fetal growth restriction and evidence of maternal antifetal rejection. Moreover, these groups could be distinguished using a small quantitative polymerase chain reaction panel and demonstrated varying influence of maternal factors on PE development. An additional subclass of PE placentas was also revealed to form because of chromosomal abnormalities in these samples, supported by array-based comparative genomic hybridization analysis. Overall, our findings represent a new paradigm in our understanding of the origins and maternal-placental contributions to the pathology of PE. The study of PE represents a unique opportunity to access human tissue associated with a complex hypertensive disorder, and our novel approach could be applied to other hypertensive and heterogeneous human diseases.

Conservative Management of Invasive Placenta Using Combined Prophylactic Internal Iliac Artery Balloon Occlusion and Immediate Postoperative Uterine Artery Embolization

Purpose

The objective of the study was to evaluate the efficacy and safety of combined prophylactic intraoperative internal iliac artery balloon occlusion and postoperative uterine artery embolization in the conservative management (uterine preservation) of women with invasive placenta undergoing scheduled caesarean delivery.

Methods

Ten women (mean age 35 years) with invasive placenta choosing caesarean delivery without hysterectomy had preoperative insertion of internal iliac artery occlusion balloons, intraoperative inflation of the balloons, and immediate postoperative uterine artery embolization with absorbable gelatin sponge. A retrospective review was performed with institutional review board approval. Outcome measures were intraoperative blood loss, transfusion requirement, hysterectomy rate, endovascular complications, surgical complications, and postoperative morbidity.

Results

All women had placenta increta or percreta, and concomitant complete placenta previa. Mean gestational age at delivery was 36 weeks. In 6 women the placenta was left undisturbed in the uterus, 2 had partial removal of the placenta, and 2 had piecemeal removal of the whole placenta. Mean estimated blood loss during caesarean delivery was 1.2 L. Only 2 patients (20%) required blood transfusion. There were no intraoperative surgical complications, endovascular complications, maternal deaths, or perinatal deaths. Three women developed postpartum complications necessitating postpartum hysterectomy; the hysterectomy rate was therefore 30% and uterine preservation was successful in 70%.

Conclusion

Combined bilateral internal iliac artery balloon occlusion and uterine artery embolization may be an effective strategy to control intraoperative blood loss and preserve the uterus in patients with invasive placenta undergoing caesarean delivery.

Risk threshold for starting low dose aspirin in pregnancy to prevent preeclampsia: an opportunity at a low cost

Background

Preeclampsia (PE) increases maternal and perinatal morbidity and mortality. Based on a multitude of data from randomized clinical trials, clinical practice guidelines endorse using ASA to prevent PE in women who are “at risk.” However, data are lacking about the level of absolute risk to warrant starting ASA prophylaxis.

Methods and Findings

We present two approaches for objectively determining the minimum absolute risk for PE at which ASA prophylaxis is justified. The first is a new approach—the minimum control event rate (CER_min). The second approach uses a pre-existing concept—the minimum event rate for treatment (MERT). Here we show how the CER_min is derived, and then use the CER_min and the MERT to guide us to a reasonable risk threshold for starting a woman on ASA prophylaxis against PE based on clinical risk assessment. We suggest that eligible women need not be at “high risk” for preeclampsia to warrant ASA, but rather at some modestly elevated absolute risk of 6–10%.

Conclusions

Given its very low cost, its widespread availability, ease of administration and its safety profile, ASA is a highly attractive agent for the prevention of maternal and perinatal morbidity worldwide.

Low molecular weight heparin and aspirin for recurrent pregnancy loss: results from the randomized, controlled HepASA Trial

OBJECTIVE

To compare live birth rates in women with recurrent pregnancy loss (RPL) and either autoantibodies or a coagulation abnormality, treated with low molecular weight heparin plus aspirin (LMWH/ASA) or ASA alone, and to place our results in context with other randomized clinical trials (RCT) with similar cohorts.

METHODS

The HepASA Trial was an RCT including patients with a history of RPL and at least 1 of the following: antiphospholipid antibody (aPL), an inherited thrombophilia, or antinuclear antibody. Treatment groups were stratified by aPL status and history of early versus late pregnancy losses. Patients received either LMWH/ASA or ASA alone. The primary outcome was live birth; secondary outcomes included adverse events and bone loss at the spine and femoral neck. Literature over the past 20 years was reviewed to identify comparable RCT.

RESULTS

Over 4 years, 859 women with RPL were screened: 88 (10.2%) fulfilled inclusion criteria, became pregnant and were randomized to receive either LMWH/ASA or ASA alone. aPL were present in 42 (47.7%) patients in each group. The trial was stopped after 4 years when an interim analysis showed no difference in live birth rates in the 2 groups, and a lower rate of pregnancy loss in the ASA only group than expected. In the LMWH/ASA group, 35/45 (77.8%) had a live birth versus 34/43 (79.1%) in the ASA only group (p = 0.71). Neither number of prior losses nor aPL status was correlated with pregnancy outcome. There were no cases of pregnancy related thrombosis in either group. Mean change in BMD did not differ by treatment group at either the lumbar spine (p = 0.57) or femoral neck (p = 0.15). RCT since 2000 for aPL positive women with RPL and similar inclusion criteria report a mean live birth rate of 75% with either LMWH or ASA.

CONCLUSION

LMWH/ASA did not confer incremental benefit compared to ASA alone for this population. Regardless of treatment regimen, number of prior losses, or aPL positivity, almost 80% of women in our RPL cohort had a successful pregnancy outcome. These findings contribute to a growing body of literature that contests the emerging standard of care comprising LMWH/ASA for this population.

Second-trimester prediction of severe placental complications in women with combined elevations in alpha-fetoprotein and human chorionic gonadotrophin

OBJECTIVE

The purpose of this study was to determine the ability of uterine artery Doppler and placental ultrasound to identify adverse clinical outcomes attributable to severe placental dysfunction in women with second-trimester unexplained elevated maternal serum screening of alpha-fetoprotein and human chorionic gonadotropin.

STUDY DESIGN

Fifty singleton pregnancies with elevated alpha-fetoprotein (3.5 multiples of median [range 2.1 to 10.5]) and human chorionic gonadotropin (5.3 multiples of median [range 2.5 to 21.7]) and a normal fetal anatomical ultrasound were prospectively evaluated with placental ultrasound and uterine artery Doppler at referral between 19 and 23 weeks' gestation.

RESULTS

Abnormalities in both placental ultrasound and uterine artery Doppler (n = 24) predicted preterm delivery less than 32 weeks from any cause (n = 24) (75% sensitivity, 75% positive predictive value; likelihood ratio positive 3.3 [1.6 to 6.8]), intrauterine fetal death (n = 12) (100% sensitivity, 50% positive predictive value; likelihood ratio positive 3.1 [2.0 to 5.0]), and intrauterine growth restriction with absent/reversed end-diastolic flow (n = 17) (sensitivity 94%, positive predictive value 67%, likelihood ratio positive 3.9 [2.0 to 6.2]) . Ischemic-thrombotic pathology was present in 88% of placentas examined (n = 32).

CONCLUSION

Uterine artery Doppler and placental morphology identified most pregnancies with combined abnormal maternal serum screening destined to result in extremely premature delivery and/or perinatal death. Abnormal maternal serum screening reports could include a recommendation for placental ultrasound testing when no fetal explanation has been identified.

Undernutrition during the first half of gestation increases the predominance of fetal tissue in late-gestation ovine placentomes

OBJECTIVE

To investigate, in sheep, the effects of maternal undernutrition during the first half of pregnancy on placental growth and development and fetal growth.

STUDY DESIGN

Six ewes (R) were subjected to a 15% reduction in nutrient intake for the first 70 days of gestation and thereafter received the recommended daily intake. Another group of six ewes (C) received the recommended daily intake throughout pregnancy. At 130 days gestation the ewes were killed and morphological and morphometrical measurements were carried out on the placenta and fetus.

RESULTS

Undernutrition resulted in a significant alteration in placental morphology, which was seen as increased growth of the fetal side of the placenta in R animals. However, fetal size in late gestation was not affected by the undernutrition, suggesting that placental adaptation was successful in maintaining fetal growth.

CONCLUSION

Placental adaptations, including changes in gross morphology, may preserve fetal growth if maternal undernutrition is not severe. The mechanisms remain to be elucidated.

Macrophage-induced apoptosis limits endovascular trophoblast invasion in the uterine wall of preeclamptic women

Impaired invasion of uteroplacental arteries by extravillous trophoblast cells is a key pathogenic mechanism of preeclampsia. We previously demonstrated that reduced trophoblast invasion into uteroplacental spiral arteries was associated with an excess of macrophages in and around these arteries. To explore the significance of these observations, we correlated the extent of extravillous trophoblast apoptosis in placental bed biopsy specimens with macrophage distribution and studied the effect of macrophages upon trophoblast apoptosis in vitro. Extravillous trophoblast hybrid cells were cocultured with activated macrophages exposed to exogenous tumor necrosis factor alpha (TNFalpha), anti-tumor necrosis factor receptor I (TNF-RI), and tryptophan depletion, and the rates of trophoblast apoptosis were measured. Extravillous trophoblast hybrid cells showed increased rates of apoptosis following exposure to exogenous TNFalpha, with tryptophan depletion, and when cocultured with activated macrophages. The proapoptotic effects of macrophages in vitro were completely inhibited only by simultaneous addition of tryptophan and anti-TNF-RI. Our data indicate that macrophages, residing in excess in the placental bed of preeclamptic women, are able to limit extravillous trophoblast invasion of spiral arterial segments through apoptosis mediated by the combination of TNFalpha secretion and tryptophan depletion. The mechanisms by which macrophages are activated and recruited to the placental bed are presently unknown but are likely central to the pathogenesis of preeclampsia.

Effect of early maternal iron stores on placental weight and structure

BACKGROUND

Large placental size and low birthweight have been implicated as factors predicting high blood pressure in adulthood. Maternal anaemia has been suggested as a link. We investigated the interaction between maternal iron status and other factors known to influence birthweight and placental size.

METHODS

In a prospective study of 1650 low-risk, singleton, caucasian pregnancies, we related placental size and birthweight to maternal iron status, socioeconomic status, and parity. Placental morphology was assessed in 17 randomly chosen primigravid pregnancies.

FINDINGS

Parity was an important determinant of birthweight (mean standard deviation score -0.13 [SD 0.90] para 0; -0.24 [0.90] para 1; 0.32 [1.1] para 2; 0.21 [1.1] para > or = 3; p<0.0001) and placental weight (mean 655 g [SD 130]; 679 g [122]; 675 g [139]; 694 g [157], respectively; p=0.01). Cigarette smoking influenced birthweight only. Socioeconomic status had little effect after correction for parity. In addition to parity, the factors influencing placental weight were maternal height, weight, and serum ferritin concentration at booking, but not haemoglobin concentration. Serum ferritin concentrations were associated with folate intake and parity. In the placental morphology subset, serum ferritin concentration was inversely related to overall measures of peripheral villous capillarization. Haemoglobin concentration showed no such association.

INTERPRETATION

These findings show a relation between maternal anaemia and placental size and birthweight across the normal range for these measures. Low ferritin concentrations in early pregnancy were associated with increased placental vascularisation at term. The association between ferritin concentration and folate supplementation emphasises the importance of preconceptional health, particularly in women at high risk of iron deficiency.

Ontogeny of beta 2 glycoprotein I and annexin V in villous placenta of normal and antiphospholipid syndrome pregnancies

beta2-glycoprotein I (beta2GPI) and annexin V (AV) have been implicated in the pathophysiology of the antiphospholipid syndrome (APS). We investigated their placental expression in normal villous tissues throughout gestation; first trimester n = 10, early second trimester; n = 4, preterm; n = 5) and term; n = 7 and in APS (2 first trimester, 1 preterm and 8 term deliveries). beta2GPI and AV were both expressed by the placenta from as early as seven weeks gestation and were colocalised to the syncytiotrophoblast. beta2GPI staining was also observed in stromal cells, being present in phagocytic Hofbauer cells and surrounding newly formed fetal vessels in a perivascular pattern, from seven to seventeen weeks gestation. An abnormal morphological distribution of AV was noted in one first trimester APS placenta, and for beta2GPI in a further first trimester placenta. When placental proteins were extracted from villous tissue, the concentration of AV/mg protein in term APS placentas (median, interquartile range) (aPS; 8.16, 7.879.72 microg/mg) was significantly higher (p <0.005) than normal term levels (normal; 2.47, 2.28-2.54 microg/mg). beta2GPI increased with advancing gestation (first trimester; 0.93, 0.64-1.26 microg/mg, term; 3.67, 2.58-4.48 microg/mg) in normal pregnancy. Term APS placentas had a reduced beta2GPI content (2.31, 1.87-2.49 microg/mg), p <0.05. The placental role of these proteins remains to be identified.

Fetal cerebral blood flow redistribution in late gestation: identification of compromise in small fetuses with normal umbilical artery Doppler

OBJECTIVE

To evaluate the role of middle cerebral artery Doppler in small fetuses during the late third trimester.

DESIGN

Prospective observational study of structurally normal fetuses with an estimated fetal weight < 5th percentile for gestation. Perinatal outcome was determined using a structured datasheet sent to each referring obstetrician.

SUBJECTS

Structurally normal fetuses at 35 or more weeks of gestation referred during a 2-year period to the fetal growth clinic of a regional fetal medicine unit in North London. Fetuses with aneuploidy and/or major structural abnormalities were excluded.

METHODS

Umbilical artery and middle cerebral artery (MCA) Doppler waveforms were recorded and considered abnormal if above 95th or below 5th percentiles, respectively. Amniotic fluid was considered reduced if the maximum vertical cord-free pool was < 2 cm. The placenta was considered mature if the Grannum grade was II or III. The head circumference (HC)/abdominal circumference (AC) ratio was considered abnormal if > 95th percentile for gestation. Fetal growth, amniotic fluid, biophysical profile score and umbilical artery Doppler were used to advise the referring obstetrician about fetal well-being and he/she independently decided both the timing and mode of delivery.

RESULTS

Forty-seven fetuses fulfilled the entry criteria. Thirty-four (72%) demonstrated normal umbilical artery Doppler waveforms. Sixteen (34%) demonstrated middle cerebral artery redistribution, of which nine (56%) had normal umbilical artery Doppler waveforms. MCA blood flow redistribution was associated with an increased incidence of cesarean delivery and need for neonatal admission. Of all gray-scale parameters, an elevated HC/AC ratio has the strongest association with MCA blood flow redistribution (15/16 vs. 1/31; P < 0.01).

CONCLUSIONS

MCA Doppler may be a useful tool to assess the health of small fetuses in the late third trimester. Redistribution may occur in the presence of normal umbilical artery Doppler and should be suspected when the HC/AC ratio is elevated.

Oxygen and placental vascular development

Human embryogenesis takes place in a hypoxic environment because the trophoblast shell excludes entry of maternal blood. The first fetal-placental villi develop as trophoblast sprouts. These are invaded by allantoic mesoderm to form secondary villi and are transformed, by vasculogenesis, into tertiary villi. The placental barrier to maternal blood is gradually breached between 8-12 weeks of gestation, due to invasion of placental-bed uteroplacental spiral arteries by the extravillous trophoblast (EVT). Placental oxygen tension thus rises and a phase of branching angiogenesis continues until 24 weeks. Thereafter a gradual shift takes place favoring non-branching angiogenesis. Gas-exchanging terminal villi thus form which are essential for rapid fetal growth and development of a high-flow, low-resistance fetal-placental circulation. Inadequate invasion of the uteroplacental spiral arteries by EVT results in placental ischemia and the development of obstetrical complications--preeclampsia and/or intrauterine growth restriction (IUGR). Placental villi often show evidence of continued branching angiogenesis, as is the case with anemic pregnancy, and pregnancy at high altitude. These structural alterations may reflect continued hypoxia-driven activity of vascular endothelial growth factor (VEGF). By contrast, a minority of severe early-onset IUGR pregnancies exhibit reduced fetal-placental blood flow with elongated maldeveloped villous capillaries. Placenta-like growth factor (PIGF) expression is increased while trophoblast proliferation is reduced, suggesting "hyperoxia" in the placental villous tree. IUGR may thus have two phenotypes--a more common hypoxic and a rarer hyperoxic type. While this concept is gaining acceptance, we have no insight as to the initiating mechanism(s).

Affinity purified human antiphospholipid antibodies bind normal term placenta

Antiphospholipid antibodies (aPL) are associated with an increased incidence of fetal loss, but the pathophysiology remains unclear. One mechanism may involve the binding of aPL directly to the placenta where they may initiate placental thrombosis and infarction. We have developed an immunofluorescent technique to detect human aPL binding to human placenta. Endogenous immunoglobulins were eluted by extensive washing and residual staining was prevented by incorporating multiple blocking steps. APL were affinity purified on both cardiolipin and phosphatidylserine liposomes from the sera of six patients with aPL (five antiphospholipid syndrome (APS) patients and one post bone marrow transplant patient). Heterogeneous binding to normal term placenta, involving either the trophoblast microvillous surface, stromal and peri-vascular regions was demonstrated by affinity purified aPL from five of six patients. Preliminary sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting studies have demonstrated that aPL bind a number of placental proteins. beta2GPI was not the predominant protein bound by aPL using this technique. This study provides further evidence for the involvement of aPL in mediating placental damage.

Maternal cardiolipin, beta 2-glycoprotein-I and prothrombin antibody expression in high-risk pregnancies with bilateral abnormal uterine artery Doppler waveforms

OBJECTIVE

To compare the frequency of maternal serum antiphospholipid antibodies (to cardiolipin, beta 2-glycoprotein I and prothrombin) in pregnancies presenting with bilateral abnormal uterine artery Doppler waveforms.

DESIGN

Retrospective analysis of stored serum.

SUBJECTS

Cases comprised 47 singleton pregnancies with bilateral abnormal uterine artery Doppler waveforms at 24 weeks of gestation, followed from 20 weeks, and controls were 100 healthy pregnancies with normal uterine artery Doppler waveforms.

METHODS

Ultrasound examination utilized a 5-MHz curvilinear transabdominal transducer with pulsed and color Doppler facilities. Antiphospholipid antibodies were analyzed by ELISA methodology, and reference ranges were established using the geometric mean +/- 2 SD of healthy non-pregnant adults. Human chorionic gonadotropin (hCG) levels were obtained from patient notes.

RESULTS

Anticardiolipin antibodies were detected in 11 (23%) of the cases (IgG, n = 7; IgM, n = 6) compared with ten (10%) of the controls (p < 0.05). Low titer anticardiolipin IgG (range, 5.5-35.3; median, 6.3 GPL units) and anticardiolipin IgM (range, 3.4-14.7; median, 5.3 MPL units) were detected in cases. Amongst the cases, adverse perinatal outcomes were more common in the presence of raised levels of anticardiolipin antibodies. Anti-beta 2-glycoprotein I IgG was not detected in any of the cases. Antiprothrombin IgG was not detected, but antiprothrombin IgM occurred in 10.6% of cases compared with 2% of controls.

CONCLUSIONS

Women with persistent bilateral abnormal uterine artery. Doppler waveforms in mid-gestation were more likely to express raised levels of anticardiolipin antibodies than healthy controls with normal uteroplacental perfusion. Anticardiolipin antibodies without anti-beta 2-glycoprotein I binding may be involved in the pathogenesis of uteroplacental ischemia in a proportion of high-risk pregnancies.

Intrauterine growth restriction is associated with persistent juxtamedullary expression of renin in the fetal kidney

BACKGROUND

Intrauterine growth restriction (IUGR) has been linked to impaired renal function and hypertension, suggesting that an adverse prenatal environment could alter kidney development and renin production.

METHODS

Immunohistochemistry and in situ hybridization were employed to localize renin-containing cells (RCCs) in the deep, middle, and superficial zones of autopsy kidney sections, in parallel with histologic maturation, from unexplained stillborn fetuses of normal weight (N = 26) and stillborn fetuses with IUGR (N = 17).

RESULTS

In the control group, the number of RCC per 100 glomeruli in the deep zone decreased with advancing gestation from 40 at 20 weeks gestation to five at term (P < 0.001), whereas the opposite change was found in the superficial zone (increase from 5 per 100 to 55 per 100; P < 0.001). In the IUGR group, the density of RCCs in both the superficial and deep zones was similar to the control group at 20 weeks, and no shift in renin gene expression was observed as gestation advanced. Histologic maturation was unaltered.

CONCLUSIONS

Renin gene expression persists and predominates in the deep renal cortex of the stillborn IUGR fetus, and could contribute to the pathogenesis of neonatal oliguria and/or hypertension during postnatal life.