Association of non-reassuring fetal heart rate and fetal acidosis with placental histopathology

The Placenta and Neonatal Encephalopathy with a Focus on Hypoxic-Ischemic Encephalopathy

Background: Placental examination is important for its diagnostic immediacy to correlate with maternal and/or fetal complications and parturitional difficulties. In a broader context, clinicopathologic studies of the placenta have addressed a range of pathogenetic questions that have led to conclusive and inconclusive results and interpretations. Methods: Recent standardized morphologic criteria and terminology of placental lesions have facilitated the ability to compare findings from studies that have focused on complications and outcomes of pregnancy. This review is an evaluation of recent studies on placental lesions associated with hypoxic-ischemic encephalopathy (HIE). Conclusion: No apparent consensus exists on whether it is fetal inflammation with the release of cytokines or chronic maternal and/or fetal vascular malperfusion is responsible for HIE with a lowering of the threshold for hypoxic ischemia. The counter argument is that HIE occurs solely as an intrapartum event. Additional investigation is necessary.

Maternal fever in labor: etiologies, consequences, and clinical management

Intrapartum fever is common and presents diagnostic and treatment dilemmas for the clinician. True maternal sepsis is rare; only an estimated 1.4% of women with clinical chorioamnionitis at term develop severe sepsis. However, the combination of inflammation and hyperthermia adversely impacts uterine contractility and, in turn, increases the risk for cesarean delivery and postpartum hemorrhage by 2- to 3-fold. For the neonate, the rates of encephalopathy or the need for therapeutic hypothermia have been reported to be higher with a maternal fever >39°C when compared with a temperature of 38°C to 39°C (1.1 vs 4.4%; P<.01). In a large cohort study, the combination of intrapartum fever and fetal acidosis was particularly detrimental. This suggests that intrapartum fever may lower the threshold for fetal hypoxic brain injury. Because fetal hypoxia is often difficult to predict or prevent, every effort should be made to reduce the risk for intrapartum fever. The duration of exposure to epidural analgesia and the length of labor in unmedicated women remain significant risk factors for intrapartum fever. Therefore, paying careful attention to maintaining labor progress can potentially reduce the rates of intrapartum fever and the risk for cesarean delivery if fever does occur. A recent, double-blind randomized trial of nulliparas at >36 weeks' gestation demonstrated that a high-dose oxytocin regimen (6×6 mU/min) when compared with a low-dose oxytocin regimen (2×2 mU/min) led to clinically meaningful reductions in the rate of intrapartum fever (10.4% vs 15.6%; risk rate, 0.67; 95% confidence interval, 0.48-0.92). When fever does occur, antibiotic treatment should be initiated promptly; acetaminophen may not be effective in reducing the maternal temperature. There is no evidence that reducing the duration of fetal exposure to intrapartum fever prevents known adverse neonatal outcomes. Therefore, intrapartum fever is not an indication for cesarean delivery to interrupt labor with the purpose of improving neonatal outcome. Finally, clinicians should be ready for the increased risk for postpartum hemorrhage and have uterotonic agents on hand at delivery to prevent delays in treatment.

Placental pathology and neonatal outcomes in pre-eclampsia with gestational diabetes mellitus

OBJECTIVE

To investigate histopathological placental lesions and adverse neonatal outcomes by Pre-eclampsia (PE) with Gestational Diabetes Mellitus (GDM).

METHODS

This was a retrospective cohort study of pregnancies with PE delivered between 1 January 2012 to 1 January 2014. Pregnant women with PE were recruited, and divided into PE with GDM (PE + GDM) group (n = 278) and PE without GDM (PE - GDM) group (n = 586). We compared the placental pathology and neonatal outcomes between the two groups.

RESULTS

The (PE + GDM) group was significantly associated with high placenta weight (534.8 ± 124.1 vs 519.3 ± 132.3 g, p = .011), the large diameter of the placenta (17.8 ± 2.2 vs 16.2 ± 2.7 cm, p = .016) than (PE - GDM) group. The incidence of chorioamnionitis in (PE + GDM) group was significantly higher than (PE - GDM) group [48.9% (136/278) vs 41.5% (243/586), p = .028], whereas there were no significant differences in umbilical cord length and infarction between the two groups. The (PE + GDM) group had a higher rate of prematurity [44.9% (125/278) vs 39.9% (234/586), p = .042] than (PE - GDM) group, in (PE + GDM) group the incidence of LGA [15.1% (42/278) vs 1.0% (6/586), p = .034], RDS [18.7% (52/278) vs 9.2% (54/586), p = .011] and hyperbilirubinemia [10.7% (30/278) vs 1.0% (6/586), p = .038] were higher than (PE - GDM) group.

CONCLUSIONS

GDM increased the offspring's complication in pregnancy with PE, the potential mechanism might be that GDM increased the placenta inflammation.

The role of placental histopathological lesions in predicting recurrence of preeclampsia

OBJECTIVE

We aimed to study the role of placental pathology in the prediction of preeclampsia (PE) recurrence.

METHODS

The medical records and pathological placental reports of all women diagnosed with PE, during 2008-2015, were reviewed. The study population was divided according to the outcome of their subsequent pregnancy: those who did (recurrence group) or did not (no-recurrence group) develop recurrent PE. Data regarding maternal characteristics and placental maternal/fetal vascular malperfusion lesions, of the initial pregnancies, were compared. Two prediction models were generated for PE recurrence.

RESULTS

Compared to the no-recurrence group (n = 130), the recurrence group (n = 96) was characterized by lower gestational age (p < 0.001), longer inter-pregnancy interval (p = 0.012), and higher rate of severe features (p < 0.001). By logistic regression analysis composite maternal (aOR = 3.05, 95%CI 1.39-6.71, p = 0.005), fetal (aOR = 9.31, 95%CI 3.9-22.1, p < 0.001), and concurrent maternal + fetal (aOR = 13.94, 95%CI 5.08-38.21, p < 0.001), vascular malperfusion lesions were found to be independently associated with recurrence. A clinical prediction model accounted for 20.8% of PE recurrence (R²  = 0.208, AUC = 0.732), while a clinical-pathological model accounted for 34.2% of recurrence (R²  = 0.342, AUC = 0.80).

CONCLUSION

Placental maternal and fetal vascular malperfusion lesions are independently associated with increased risk for PE recurrence. A clinical-pathological prediction model for recurrence of PE is superior to a prediction model based merely on clinical factors. © 2016 John Wiley & Sons, Ltd.

The effects of maternal smoking on pregnancy outcome and placental histopathology lesions

OBJECTIVE

To study the effects of maternal smoking on pregnancy outcome and placental histopathology findings.

MATERIALS & METHODS

Maternal and labor characteristics and pathological reports were compared between term placentas of complicated and uncomplicated pregnancies of: heavy smokers (>10 cigarettes per day, H-smokers), moderate smokers (<10 cigarettes per day, M-smokers) and non-smokers (controls, N-smokers).

RESULTS

Birth-weights were lower in the H-smokers and M-smokers as compared to the N-smokers (p<0.001), with a higher rate of small for gestational age (SGA): 18.2%, 19.2% and 11.4%, respectively (p=0.01). Deliveries among smokers were characterized by higher rates of abnormal fetal heart rate tracings during labor as compared to non-smokers (p=0.01). Rates of placental maternal and fetal stromal-vascular supply lesions was similar between the groups.

CONCLUSIONS

Maternal smoking is associated with higher rates of SGA. Tobacco's potential influence is probably through the disruption of normal placental epigenetic patterns, not expressed in placental histopathology lesions.

Meconium aspiration syndrome: a role for fetal systemic inflammation

BACKGROUND

Meconium aspiration syndrome (MAS) is a leading cause of morbidity and mortality in term infants. Meconium-stained amniotic fluid (MSAF) occurs in approximately 1 of every 7 pregnancies, but only 5% of neonates exposed to MSAF develop MAS. Why some infants exposed to meconium develop MAS while others do not is a fundamental question. Patients with MSAF have a higher frequency of intraamniotic inflammation/infection than those with clear fluid. We propose that fetal systemic inflammation is a risk factor for the development of MAS in patients with MSAF.

OBJECTIVE

We sought to investigate whether intraamniotic inflammation and funisitis, the histopathologic landmark of a fetal inflammatory response, predispose to MAS.

STUDY DESIGN

A prospective cohort study was conducted from 1995 through 2009. Amniotic fluid (AF) samples (n = 1281) were collected at the time of cesarean delivery from women who delivered singleton newborns at term (gestational age ≥38 weeks). Intraamniotic inflammation was diagnosed if the AF concentration of matrix metalloproteinase-8 was >23 ng/mL. Funisitis was diagnosed by histologic examination if inflammation was present in the umbilical cord.

RESULTS

The prevalence of MSAF was 9.2% (118/1281), and 10.2% (12/118) of neonates exposed to MSAF developed MAS. There were no significant differences in the median gestational age or umbilical cord arterial pH at birth between neonates who developed MAS and those who did not (each P > .1). Mothers whose newborns developed MAS had a higher median of AF matrix metalloproteinase-8 (456.8 vs 157.2 ng/mL, P < .05). Newborns exposed to intraamniotic inflammation had a higher rate of MAS than those who were not exposed to intraamniotic inflammation [13.0% (10/77) vs 0% (0/32), P = .03], as did those exposed to funisitis [31.3% (5/16) vs 7.3% (6/82); relative risk, 4.3; 95% confidence interval, 1.5-12.3]. Among the 89 newborns for whom both AF and placental histology were available, MAS was more common in patients with both intraamniotic inflammation and funisitis than in those without intraamniotic inflammation and funisitis [28.6% (4/14) vs 0% (0/28), P = .009], while the rate of MAS did not show a significant difference between patients with intraamniotic inflammation alone (without funisitis) and those without intraamniotic inflammation and funisitis [10.9% (5/46) vs 0% (0/28)].

CONCLUSION

The combination of intraamniotic inflammation with fetal systemic inflammation is an important antecedent of MAS. This concept has implications for the understanding of the mechanisms of disease responsible for MAS and for the development of prognostic models and therapeutic interventions for this disorder.

Placental pathology is associated with severity of neonatal encephalopathy and adverse developmental outcomes following hypothermia

OBJECTIVE

Although neonatal encephalopathy (NE) due to perinatal asphyxia accounts for a notable proportion of brain injury, the causal pathway remains largely unexplained. We sought to determine the association of placental pathology with: (1) severity of NE in the first 6 hours postnatal, and (2) abnormal neurodevelopmental outcomes (NDO) in neonates requiring hypothermia therapy.

STUDY DESIGN

This is a retrospective cohort study of neonates ≥36 weeks' gestation born at Parkland Hospital, Dallas, TX, from January 2006 through November 2011 with NE. Placental histology was reviewed and validated by a pediatric pathologist blinded to outcomes. Abnormal NDO was defined as death or Bayley-III score of <85 at 18-24 months of age.

RESULTS

Of 86,274 neonates ≥36 weeks' gestation, 120 had evidence of a combination of perinatal acidosis and NE. In all, 47 had mild NE and received no treatment, while 73 had moderate (n = 70) or severe (n = 3) NE and received systemic hypothermia. Nine neonates died and all survivors receiving hypothermia had a Bayley-III assessment at 22 ± 7 (SD) months of age. Chorioamnionitis with or without fetal response and patchy/diffuse chronic villitis were found to be independently associated with severity of NE (P < .001). Univariate logistic regression revealed an association with a diagnosis of major placental pathology (odds ratio, 3.5; 95% confidence interval, 1.1-11.4) and abnormal outcomes following cooling. Specifically, diffuse chronic villitis (odds ratio, 9.29; 95% confidence interval, 1.11-77.73) was the only individual predictor of abnormal NDO following hypothermia therapy.

CONCLUSION

Placental inflammatory villitis appears to be a harbinger of abnormal outcomes in neonates with NE, spanning to the 18-24 month NDO.

The role of the placenta in feto-neonatal infections

The placenta and membranes may be infected by ascending bacteria from the maternal birth canal or by bacteria, virus and protozoa via haematogenous spread. The maternal and fetal inflammatory reactions, elicited by these microorganisms, are often associated with precise anatomo-pathological findings. Furthermore, it has been demonstrated a strong relationship between placental inflammation and important perinatal adverse outcomes, including neurologic impairment and chronic lung disease. For this reason, placenta examination is an important approach for understanding infection and/or inflammation leading to fetal inflammatory response syndrome. For instance, chorioamnionitis caused by ascending infections are characterized mainly by polymorphonuclear leucocytic infiltration of the extraplacental membranes, firstly involving the lower-pole of the amniotic sac, then the intervillous space and later the chorionic plate. In fact, there is an initial "maternal inflammatory response" (MIR) to the infection and leucocytes migrate from the maternal blood stream. Subsequently, the chorionic plate is infiltrated by leucocytes derived from the fetal vessels, and this event characterizes the "fetal inflammatory response" (FIR). The release of proinflammatory cytokines and chemokines within the gestational sac is the leading cause of fetal and neonatal damage. In conclusion, certain placental reaction patterns may identify and estimate the risk for specific perinatal complications in infants.

Placental pathology in full-term infants with hypoxic-ischemic neonatal encephalopathy and association with magnetic resonance imaging pattern of brain injury

OBJECTIVE

To investigate the relationship between placental pathology and pattern of brain injury in full-term infants with neonatal encephalopathy after a presumed hypoxic-ischemic insult.

STUDY DESIGN

The study group comprised full-term infants with neonatal encephalopathy subsequent to presumed hypoxia-ischemia with available placenta for analysis who underwent cerebral magnetic resonance imaging (MRI) within the first 15 days after birth. Macroscopic and microscopic characteristics of the placenta were assessed. The infants were classified according to the predominant pattern of brain injury detected on MRI: no injury, predominant white matter/watershed injury, predominant basal ganglia and thalami (BGT) injury, or white matter/watershed injury with BGT involvement. Maternal and perinatal clinical factors were recorded.

RESULTS

Placental tissue was available for analysis in 95 of 171 infants evaluated (56%). Among these 95 infants, 34 had no cerebral abnormalities on MRI, 27 had white matter/watershed injury, 18 had BGT injury, and 16 had white matter/watershed injury with BGT involvement. Chorioamnionitis was a common placental finding in both the infants without injury (59%) and those with white matter/BGT injury (56%). On multinomial logistic regression analysis, white matter/watershed injury with and without BGT involvement was associated with decreased placental maturation. Hypoglycemia was associated with an increased risk of the white matter/BGT injury pattern (OR,5.4; 95% CI, 1.4-21.4). The BGT injury pattern was associated with chronic villitis (OR, 12.7; 95% CI, 2.4-68.7). A placental weight <10th percentile appeared to be protective against brain injury, especially for the BGT pattern (OR, 0.1; 95% CI, 0.01-0.7).

CONCLUSION

Placental weight <10th percentile was mainly associated with normal cerebral MRI findings. Decreased placental maturation and hypoglycemia <2.0 mmol/L were associated with increased risk of white matter/watershed injury with or without BGT involvement. Chronic villitis was associated with BGT injury irrespective of white matter injury.

The association of cerebral palsy with birth asphyxia: a definitional quagmire

AIM

The aim of this study was to investigate whether current literature provides a useful body of evidence reflecting the proportion of cerebral palsy (CP) that is attributable to birth asphyxia.

METHOD

We identified 23 studies conducted between 1986 and 2010 that provided data on intrapartum risks of CP.

RESULTS

The proportion of CP with birth asphyxia as a precursor (case exposure rate) varied from less than 3% to over 50% in the 23 studies reviewed. The studies were heterogeneous in many regards, including the definitions for birth asphyxia and the outcome of CP.

INTERPRETATIONS

Current data do not support the belief, widely held in the medical and legal communities, that birth asphyxia can be recognized reliably and specifically, or that much of CP is due to birth asphyxia. The very high case exposure rates linking birth asphyxia to CP can probably be attributed to several factors: the fact that the clinical picture at birth cannot specifically identify birth asphyxia; the definition of CP employed; and confusion of proximal effects - results - with causes. Further research is needed.

Two-dimensional and three-dimensional Doppler assessment of fetal growth restriction with different severity and onset

OBJECTIVES

To investigate the role of three-dimensional (3D) power Doppler ultrasonography in the assessment of fetal growth-restriction (FGR) with various degrees of severity and onset, and compare the results with the analysis of two-dimensional (2D) Doppler.

STUDY DESIGN

Vascular indices extracted from 3D Doppler measurements of the placenta were compared with indices of flow-velocity waveforms extracted from 2D Doppler measurements of the major sites of the fetal circulation between FGR (study group) and uncomplicated pregnancies (control group) from 25 to 38 weeks' gestation.

RESULTS

Three-dimensional indices were significantly lower in pregnancies complicated by FGR compared with uncomplicated pregnancies. When measured in placental periphery, vascularization index was 9.4 ± 9.6 in FGR pregnancies compared with 16 ± 14.7, P = 0.04. Flow index was 33.9 ± 6.9 compared with 38.7 ± 4.9, P = 0.03 and the vascularization-flow index was 3.8 ± 4.3 compared with 6.5 ± 6, respectively, P = 0.03. Among the conventional 2D indices, umbilical artery and middle cerebral artery pulsatility indices were not significantly different between the FGR and control groups. Higher rate of maternal or fetal compartment vascular lesions were detected in the FGR group.

CONCLUSIONS

Three-dimensional Doppler was found to be more strongly associated with placental vascular compromise than conventional 2D Doppler, regardless of severity and onset of fetal growth restriction.

Epidural analgesia and maternal fever: a clinical and research update

PURPOSE OF REVIEW

Maternal fever following epidural analgesia complicates up to one-third of nulliparous labors. Although generally benign, maternal fever is associated with both excess healthcare costs and an increased risk of adverse maternal and neonatal outcomes; therefore, this topic is of interest to anesthesiologists, obstetricians and pediatricians alike. The purpose of this review is to examine the latest research on the topic of epidural-related maternal fever, with special focus on the clinical relevance of new information.

RECENT FINDINGS

Research over the past 18 months has increased our understanding of the cause of epidural-related fever and brought additional supportive evidence that proactive labor management may decrease risk. Additionally, there were innovative investigations of potential pharmacologic interventions to reduce maternal, and potentially fetal, risk.

SUMMARY

Significant research advances were made in the last 18 months around the topic of epidural-related fever, but major gaps in knowledge persist especially with understanding the precise mechanism. The most pressing area of research is the development of well tolerated and effective prophylactic interventions to prevent maternal and fetal exposure to hyperthermia and inflammation.

Neurodiagnostic techniques in neonatal critical care

This article reviews recent advances in the neurodiagnostic tools available to clinicians practicing in neonatal critical care. The advent of induced mild hypothermia for acute neonatal hypoxic-ischemic encephalopathy in 2005 has been responsible for renewed urgency in the development of precise and reliable neonatal neurodiagnostic techniques. Traditional evaluations of bedside head ultrasounds, head computed tomography scans, and routine electroencephalograms (EEGs) have been upgraded in most tertiary pediatric centers to incorporate protocols for MRI, continuous EEG monitoring with remote bedside access, amplitude-integrated EEG, and near-infrared spectroscopy. Meanwhile, recent studies supporting the association between placental pathology and neonatal brain injury highlight the need for closer examination of the placenta in the neurodiagnostic evaluation of the acutely ill newborn. As the pursuit of more effective neuroprotection moves into the "hypothermia plus" era, the identification, evaluation, and treatment of the neurologically affected newborn in the neonatal intensive care unit has increasing significance.

Placental factor in spontaneous term labor in uncomplicated pregnancy

OBJECTIVES

To investigate the placental role in uncomplicated pregnancies and spontaneous term labor.

METHODS

Placentas were retrieved from women with uncomplicated pregnancies and compared between those with spontaneous term labor to those with elective cesarean delivery without labor. Placentas were analyzed for lesions consistent with maternal circulation abnormalities, lesions consistent with fetal thrombo-occlusive disease and inflammatory lesions, maternal or fetal responses.

RESULTS

The study included 139 pregnancies, 76 with term spontaneous deliveries (cases) and 63 with term elective cesarean deliveries (controls). Maternal age, gravidity, parity and BMI were significantly lower in the study group, but gestational age was higher as compared with the control group. Higher rate of maternal inflammatory lesions was observed in the study group compared to the control group, 21 vs. 1.6%, respectively, p = 0.001. No differences were observed in vascular lesions or in fetal inflammatory lesions between the groups.

CONCLUSION

Placental maternal inflammatory changes play a role in spontaneous term labor, different from the involvement of the fetal compartment and placental vascular component in preterm labor.

The association of histologic placental inflammation with category II fetal heart tracings

The present study assessed whether placentas in women delivered by cesarean for category II fetal heart tracings (FHT) exhibit a higher incidence of acute inflammation than those of women delivered by cesarean for labor arrest. This case control study included singleton pregnancies ≥36 weeks of gestation delivered by cesarean for an FHT indication (cases) or because of labor arrest (controls) 2005-2009 at Prentice Women's Hospital. Exclusions were maternal diabetes, hypertension, known thrombophilia, connective tissue disorders, clinical evidence of chorioamnionitis, placental abruption, fetal anomalies, stillbirth, or an infant with a birth weight less than the 10th percentile. Women were included in the case group if the indication for cesarean delivery was based on the FHT and review of the FHT determined that they were designated as category II prior to delivery. A perinatal pathologist, unaware of indications for delivery, assessed placental inflammation in maternal and fetal compartments. Stage and grade of acute inflammation, from none to severe (scored 0-3), in the membranes, chorionic plate, chorionic vessels, and umbilical cord were assessed, and overall maternal and fetal inflammatory stages were assigned. Findings indicative of chronic inflammation were also noted. Other than lower umbilical artery cord gases in women with category II FHT, cases (n  =  51) and controls (n  =  27) had similar baseline characteristics and newborn outcomes, as well as similar placental pathologic findings. In uncomplicated patients, the presence or extent of placental inflammation does not appear to differ between women delivered for category II FHT and labor arrest.

The placental component in early-onset and late-onset preeclampsia in relation to fetal growth restriction

OBJECTIVE

To identify pathological placental differences between early-onset and late-onset preeclampsia, in relation to fetal growth restriction (FGR).

METHODS

Placentas from patients with preeclampsia were analyzed for lesions of maternal vascular supply consistent with maternal underperfusion and lesions of fetal vascular supply consistent with fetal thrombo-occlusive disease. Findings were compared between patients who gave birth before 34 weeks (early-onset preeclampsia) and after 34 weeks (late-onset preeclampsia).

RESULTS

Compared with the late-onset group (n = 93), the early-onset group (n = 37) had higher rates of FGR (62.2% vs 25.8%, P < 0.001) and lesions of maternal vascular supply (95% vs 60%, P < 0.001). Within the early-onset group, cases with FGR (n = 23) had more lesions of fetal vascular supply (47.8% vs 7%, P = 0.01), with similar high rates of lesions of maternal vascular supply (91% vs 100%) compared with those without FGR. Within the late-onset preeclampsia group, cases with FGR (n = 24) had higher rates of maternal vascular supply lesions (88% vs 51%, P = 0.003) than those without FGR, but similar rates of fetal vascular supply lesions (25% vs 16%, P = 0.32).

CONCLUSION

The placental fetal vascular supply lesions in combination with maternal vascular lesions are more dominant in early-onset preeclampsia with FGR as compared with early-onset preeclampsia without FGR.

Reactivity of blood vessels in response to prostaglandin E2 in placentas from pregnancies complicated by fetal growth restriction

OBJECTIVE

The authors aimed to study the contractility responses of normal and fetal growth restriction (FGR) placentas to prostaglandin E(2) (PGE(2) ) and to correlate the results to subsequent placental histological analysis.

METHOD

A dual-perfused single cotyledon model was used. Placentas from pregnancies complicated by FGR and from normal pregnancies were obtained. Selected cotyledons were cannulated and dually perfused. Following stabilization, three concentrations of PGE(2) (0.05, 0.1, and 0.15 mg/mL) were administered to the fetal arterial side causing contraction/relaxation response. Fetal perfusion pressure was measured continuously during these contraction and relaxation phases. Following the perfusion experiments, the placentas were analyzed for fetal or maternal origin vascular lesions.

RESULTS

A total of 21 complete experiments were performed (16 normal, 5 FGR). In response to PGE(2) , FGR placentas exhibited lower change in the perfusion pressure and lower relaxation time constant. Basal perfusion pressure did not differ significantly between the two groups. Placental histopathology lesions, fetal or maternal origin, were more common in the FGR compared with the controls placentas, 80% versus 25%, respectively, P=  0.047.

CONCLUSIONS

The lower vascular reactivity in response to PGE(2) and the presence of fetal and maternal vascular placental lesions suggest a mechanism explaining the altered vascular supply in FGR.

The placenta and neurologic and psychiatric outcomes in the child: study design matters

Much information exists about functions of the human placenta and about potential mechanisms by which the placenta may influence human health or disease, including developmental disorders of brain. Recent studies indicate a high frequency of placental pathology in infants with developmental brain disorders, or with risk factors for such disorders. However, most clinical studies of the association of placental features with adverse neurologic or psychiatric outcome have substantial methodologic limitations. We discuss issues of study design as they relate to studies of the placenta and human brain disorders. In addition to the need for further consensus on procedures and terminology for placental evaluation, there are a number of special features that make clinical studies of the association of placental features with neurologic and psychiatric disorders especially difficult: most such disorders are not diagnosed until months or years after the majority of placentas have been discarded; these disorders are individually uncommon, so that prospective studies - needed to provide denominator data to enable estimation of risks - will require very large sample sizes; the administrative structures required to relate features of the placenta with clinical outcome will be complicated and costly. We offer some suggestions concerning study design in the face of these practical difficulties. Systematic and methodologically rigorous exploration of the role of the placenta in human developmental brain disorders has scarcely begun. A new generation of studies, difficult but potentially enormously rewarding, will be needed for clinical investigations of the placenta and fetal brain development.