Stillbirth Collaborative Research Network: design, methods and recruitment experience

Stillbirth, hypertensive disorders of pregnancy, and placental pathology

INTRODUCTION

Stillbirth, preeclampsia, and gestational hypertension (PE/GH) have similar clinical risk factors and redundant placental pathology. We aim to discern if stillbirth with PE/GH has a particular phenotype by comparing stillbirths with and without PE/GH.

METHODS

Secondary analysis of the Stillbirth Collaborative Research Network, a population-based cohort study of all stillbirths and a sample of live births from 2006 to 2008 in five catchment areas. We compared placental pathology between stillbirths and with and without PE/GH, stratified by term or preterm. We also compared placental pathology between stillbirths and live births with PE/GH.

RESULTS

79/518 stillbirths and 140/1200 live births had PE/GH. Amongst preterm stillbirths, there was higher feto-placental ratio in PE/GH pregnancies (OR 1.24 [1.11, 1.37] per unit increase), and there were more parenchymal infarctions (OR 5.77 [3.18, 10.47]). Among PE/GH pregnancies, stillbirths had increased maternal and fetal vascular lesions, including retroplacental hematoma, parenchymal infarction, fibrin deposition, fetal vascular thrombi, and avascular villi.

DISCUSSION

Stillbirth pregnancies are overwhelmingly associated with placental lesions. Parenchymal infarctions are more common in PE/GH preterm stillbirths, but there is significant overlap in lesions found in stillbirths and PE/GH.

The association of stillbirth with depressive symptoms 6-36 months post-delivery

BACKGROUND

Stillbirths (≥ 20 weeks' gestation), which account for about 1 in 200 US pregnancies, may grieve parents deeply. Unresolved grief may lead to persistent depression.

METHODS

We compared depressive symptoms in 2009 (6-36 months after index delivery) among consenting women in the Stillbirth Collaborative Research Network's population-based case-control study conducted 2006-08 (n = 275 who delivered a stillbirth and n = 522 who delivered a healthy livebirth (excluding livebirths < 37 weeks, infants who had been admitted to a neonatal intensive care unit or who died). Women scoring > 12 on the Edinburgh Depression Scale were classified as currently depressed. Crude (cOR) and adjusted (aOR) odds ratios and 95% confidence intervals [CI] were computed from univariate and multivariable logistic models, with weighting for study design and differential consent. Marginal structural models examined potential selection bias due to low follow-up.

RESULTS

Current depression was more likely in women with stillbirth (14.8%) vs. healthy livebirth (8.3%, cOR 1.90 [95% CI 1.20, 3.02]). However, after control for history of depression and factors associated with both depression and stillbirth, the stillbirth association was no longer significant (aOR 1.35 [95% CI 0.79, 2.30]). Conversely, for the 76% of women with no history of depression, a significant association remained after adjustment for confounders (aOR 1.98 [95% CI 1.02, 3.82]).

CONCLUSIONS

Improved screening for depression and referral may be needed for women's health care. Research should focus on defining optimal methods for support of women suffering stillbirth so as to lower the risk of subsequent depression.

The neuropathology of stillbirth - correlation with apolipoprotein genotype in a Scottish population based study

BACKGROUND

The neuropathology of stillbirths has been widely studied but rarely on a population basis. Whether foetal apolipoprotein E (APOE) genotype exerts any influence has been little investigated, despite well known effects in adult brains.

AIMS

To establish the neuropathology of a population cohort of stillbirths and compare with the APOE genotype.

STUDY DESIGN AND SUBJECTS

The brains of 191 stillbirths (≥24weeks of gestation) were recruited from a Scottish population cohort and grouped by clinical history. APOE genotype was available for 97%.

RESULTS AND CONCLUSIONS

One or more neuropathological features, most appearing relatively recent, were found in 54% of 157 antepartum singletons, 44% of 9 abruption-associated stillbirths, 85% of 13 in multiple pregnancies but in only 19% of 12 intrapartum stillbirths. White matter injury (WMI) occurred in 36% of preterm and 21% mature stillbirths. Fresh petechial haemorrhages were common in all groups (29%) but germinal matrix haemorrhage (GMH) (7%) and periventricular leucomalacia (1%) were confined to preterm. GMH was significantly associated with WMI (p=0.003). Placental inflammation was common in intrapartum stillbirths (50%), compared with antepartum (15%), multiple pregnancy (23%) and abruption (0%). β-Amyloid precursor protein (βAPP) positive axons (36% stillbirths overall) correlated closely with WMI (p<0.0001), justifying future routine inclusion in foetal neuropathological investigation. This study highlights the paucity of brain damage in intrapartum stillbirths. While APOE2 was significantly overrepresented in stillbirths, there was no correlation between APOE genotype and neuropathological findings. We conclude that APOE does not influence neuropathological outcomes in stillbirths.

Bile acids in a multicenter, population-based case-control study of stillbirth

OBJECTIVE

We sought to compare bile acids in women with and without stillbirth in a population-based study.

STUDY DESIGN

The Stillbirth Collaborative Research Network conducted a multisite, population-based case-control study of stillbirth (fetal deaths ≥20 weeks). Maternal sera were obtained at the time of enrollment and frozen at -80°C until assay for bile acids.

RESULTS

Assays were performed in 581 women with stillbirth and 1546 women with live births. Bile acid levels were slightly higher in women with stillbirth (geometric mean [95% confidence interval {CI}] = 3.2 [3.0-3.5]) compared to live births (2.9 [2.7-3.1], P = .0327). However, the difference was not significant after adjustment for baseline risk factors for stillbirth. The proportion of women with elevated levels (≥10 or ≥40 μmol/L) was similar in stillbirths and live births. Results were similar when the analysis was limited to subsets of stillbirths and live births. In women with stillbirths not associated with fetal anomalies or obstetric complications bile acid levels were higher than in women with term live births (geometric mean [95% CI] = 3.4 [3.0-3.8] vs 2.9 [2.7-3.0], P = .0152, unadjusted; P = .06, adjusted). However, a similar proportion of women in both groups had levels ≥10 μmol/L (10.7 vs 7.2%; odds ratio [OR], 1.54; 95% CI, 0.97-2.44; adjusted OR, 1.29; 95% CI, 0.78-2.15) and ≥40 μmol/L (1.7 vs 0.7%; OR, 2.58; 95% CI, 0.85-7.84; adjusted OR, 2.28; 95% CI, 0.79-6.56).

CONCLUSION

Our data do not support testing for bile acids in cases of stillbirth in the absence of clinical evidence of intrahepatic cholestasis of pregnancy.

Fetal growth and risk of stillbirth: a population-based case-control study

BACKGROUND

Stillbirth is strongly related to impaired fetal growth. However, the relationship between fetal growth and stillbirth is difficult to determine because of uncertainty in the timing of death and confounding characteristics affecting normal fetal growth.

METHODS AND FINDINGS

We conducted a population-based case-control study of all stillbirths and a representative sample of live births in 59 hospitals in five geographic areas in the US. Fetal growth abnormalities were categorized as small for gestational age (SGA) (<10th percentile) or large for gestational age (LGA) (>90th percentile) at death (stillbirth) or delivery (live birth) using population, ultrasound, and individualized norms. Gestational age at death was determined using an algorithm that considered the time-of-death interval, postmortem examination, and reliability of the gestational age estimate. Data were weighted to account for the sampling design and differential participation rates in various subgroups. Among 527 singleton stillbirths and 1,821 singleton live births studied, stillbirth was associated with SGA based on population, ultrasound, and individualized norms (odds ratio [OR] [95% CI]: 3.0 [2.2 to 4.0]; 4.7 [3.7 to 5.9]; 4.6 [3.6 to 5.9], respectively). LGA was also associated with increased risk of stillbirth using ultrasound and individualized norms (OR [95% CI]: 3.5 [2.4 to 5.0]; 2.3 [1.7 to 3.1], respectively), but not population norms (OR [95% CI]: 0.6 [0.4 to 1.0]). The associations were stronger with more severe SGA and LGA (<5th and >95th percentile). Analyses adjusted for stillbirth risk factors, subset analyses excluding potential confounders, and analyses in preterm and term pregnancies showed similar patterns of association. In this study 70% of cases and 63% of controls agreed to participate. Analysis weights accounted for differences between consenting and non-consenting women. Some of the characteristics used for individualized fetal growth estimates were missing and were replaced with reference values. However, a sensitivity analysis using individualized norms based on the subset of stillbirths and live births with non-missing variables showed similar findings.

CONCLUSIONS

Stillbirth is associated with both growth restriction and excessive fetal growth. These findings suggest that, contrary to current practices and recommendations, stillbirth prevention strategies should focus on both severe SGA and severe LGA pregnancies. Please see later in the article for the Editors' Summary.

Association between stillbirth and illicit drug use and smoking during pregnancy

OBJECTIVE

To compare illicit drug and smoking use in pregnancies with and without stillbirth.

METHODS

The Stillbirth Collaborative Research Network conducted a case-control study from March 2006 to September 2008, covering more than 90% of deliveries to residents of five a priori-defined geographically diverse regions. The study attempted to include all stillbirths and representative liveborn controls. Umbilical cord samples from cases and controls were collected and frozen for subsequent batch analysis. Maternal serum was collected at delivery and batch analyzed for cotinine.

RESULTS

For 663 stillbirth deliveries, 418 (63%) had cord homogenate and 579 (87%) had maternal cotinine assays performed. For 1,932 live birth deliveries, 1,050 (54%) had cord homogenate toxicology and 1,545 (80%) had maternal cotinine assays performed. A positive cord homogenate test for any illicit drug was associated with stillbirth (odds ratio [OR] 1.94, 95% confidence interval [CI] 1.16-3.27). The most common individual drug was cannabis (OR 2.34 95% CI 1.13-4.81), although the effect was partially confounded by smoking. Both maternal self-reported smoking history and maternal serum cotinine levels were associated in a dose-response relationship with stillbirth. Positive serum cotinine less than 3 ng/mL and no reported history of smoking (proxy for passive smoke exposure) also were associated with stillbirth (OR 2.06, 95% CI 1.24-3.41).

CONCLUSION

Cannabis use, smoking, illicit drug use, and apparent exposure to second-hand smoke, separately or in combination, during pregnancy were associated with an increased risk of stillbirth. Because cannabis use may be increasing with increased legalization, the relevance of these findings may increase as well.

LEVEL OF EVIDENCE

II.

Placental findings in singleton stillbirths

OBJECTIVE

To compare placental lesions for stillbirth cases and live birth controls in a population-based study.

METHODS

Pathologic examinations were performed on placentas from singleton pregnancies using a standard protocol. Data were analyzed overall and within gestational age groups at delivery.

RESULTS

Placentas from 518 stillbirths and 1,200 live births were studied. Single umbilical artery was present in 7.7% of stillbirths and 1.7% of live births, velamentous cord insertion was present in 5% of stillbirths and 1.1% of live births, diffuse terminal villous immaturity was present in 10.3% of stillbirths and 2.3% of live births, inflammation (eg, acute chorioamnionitis of placental membranes) was present in 30.4% of stillbirths and 12% of live births, vascular degenerative changes in chorionic plate were present in 55.7% of stillbirths and 0.5% of live births, retroplacental hematoma was present in 23.8% of stillbirths and 4.2% of live births, intraparenchymal thrombi was present in 19.7% of stillbirths and 13.3% of live births, parenchymal infarction was present in 10.9% of stillbirths and 4.4% of live births, fibrin deposition was present in 9.2% of stillbirths and 1.5% of live births, fetal vascular thrombi was present in 23% of stillbirths and 7% of live births, avascular villi was present in 7.6% of stillbirths and 2.0% of live births, and hydrops was present in 6.4% of stillbirths and 1.0% of live births. Among stillbirths, inflammation and retroplacental hematoma were more common in placentas from early deliveries, whereas thrombotic lesions were more common in later gestation. Inflammatory lesions were especially common in early live births.

CONCLUSIONS

Placental lesions were highly associated with stillbirth compared with live births. All lesions associated with stillbirth were found in live births but often with variations by gestational age at delivery. Knowledge of lesion prevalence within gestational age groups in both stillbirths and live birth controls contributes to an understanding of the association between placental abnormality and stillbirth.

LEVEL OF EVIDENCE

II.

Antiphospholipid antibodies in stillbirth

OBJECTIVE

To compare antiphospholipid antibodies in deliveries with and without stillbirth using a multicenter, population-based case-control study of stillbirths and live births.

METHODS

Maternal sera were assayed for immunoglobulin (Ig)G and IgM anticardiolipin and anti-β2-glycoprotein-I antibodies. Assays were performed in 582 stillbirth deliveries and 1,547 live birth deliveries.

RESULTS

Elevated levels of IgG anticardiolipin and IgG anti-β2-glycoprotein-I antibodies were associated with an approximate threefold increased odds of stillbirth (crude odds ratio [OR] 3.43, 95% confidence interval [CI] 1.79-6.60, 3.8% compared with 1.1% and OR 3.17, 95% CI 1.30-7.72, (1.9% compared with 0.6%, respectively) when all deliveries with stillbirth were compared with all deliveries with live birth. When the subset of stillbirths not associated with fetal anomalies or obstetric complications was compared with term live births, elevated IgG anticardiolipin antibodies were associated with stillbirth (5.0% compared with 1.0%; OR 5.30, 95% CI, 2.39-11.76; IgG anti-β2-glycoprotein-I antibodies (1.9% compared with 0.6%) had an OR of 3.00 (95% CI 1.01-8.90) and IgM anticardiolipin antibodies (6.0% compared with 3.0%) had an OR of 2.03 (95% CI 1.09-3.76). Elevated levels of anticardiolipin and anti-β2-glycoprotein-I antibodies were associated with a threefold to fivefold increased odds of stillbirth.

CONCLUSIONS

Our data support consideration of testing for antiphospholipid antibodies in cases of otherwise unexplained stillbirth.

LEVEL OF EVIDENCE

II.

A population-based case-control study of stillbirth: the relationship of significant life events to the racial disparity for African Americans

Stillbirths (fetal deaths occurring at ≥20 weeks' gestation) are approximately equal in number to infant deaths in the United States and are twice as likely among non-Hispanic black births as among non-Hispanic white births. The causes of racial disparity in stillbirth remain poorly understood. A population-based case-control study conducted by the Stillbirth Collaborative Research Network in 5 US catchment areas from March 2006 to September 2008 identified characteristics associated with racial/ethnic disparity and interpersonal and environmental stressors, including a list of 13 significant life events (SLEs). The adjusted odds ratio for stillbirth among women reporting all 4 SLE factors (financial, emotional, traumatic, and partner-related) was 2.22 (95% confidence interval: 1.43, 3.46). This association was robust after additional control for the correlated variables of family income, marital status, and health insurance type. There was no interaction between race/ethnicity and other variables. Effective ameliorative interventions could have a substantial public health impact, since there is at least a 50% increased risk of stillbirth for the approximately 21% of all women and 32% of non-Hispanic black women who experience 3 or more SLE factors during the year prior to delivery.

An algorithm for the estimation of gestational age at the time of fetal death

BACKGROUND

Accurate assignment of gestational age (GA) at time of fetal death is important for research and clinical practice. An algorithm to estimate GA at fetal death was developed and evaluated.

METHODS

The algorithm developed by the Stillbirth Collaborative Research Network (SCRN) incorporated clinical and post-mortem data. The SCRN conducted a population-based case-control study of women with stillbirths and livebirths from 2006 to 2008 in five geographical catchment areas. Rules were developed to estimate a due date, identify an interval during which death likely occurred, and estimate GA at the time of fetal death. Reliability of using fetal foot length to estimate GA at death was assessed.

RESULTS

The due date estimated for 620 singleton stillbirths studied was considered clinically reliable for 87%. Only 25.2% of stillbirths were documented alive within 2 days before diagnosis and 47.6% within 1 week of diagnosis. The algorithm-derived estimate of GA at time of fetal death was one or more weeks earlier than the GA at delivery for 43.5% of stillbirths. GA estimated from fetal foot length agreed with GA by algorithm within 2 weeks for 75% within a subset of well-dated stillbirths.

CONCLUSIONS

Precise assignment of GA at death, defined as reliable dating criteria and a short interval (≤1 week) during which fetal death was known to have occurred, was possible in 46.6% of cases. Fetal foot length is a relatively accurate measure of GA at death and should be collected in all stillbirth cases.

Karyotype versus microarray testing for genetic abnormalities after stillbirth

BACKGROUND

Genetic abnormalities have been associated with 6 to 13% of stillbirths, but the true prevalence may be higher. Unlike karyotype analysis, microarray analysis does not require live cells, and it detects small deletions and duplications called copy-number variants.

METHODS

The Stillbirth Collaborative Research Network conducted a population-based study of stillbirth in five geographic catchment areas. Standardized postmortem examinations and karyotype analyses were performed. A single-nucleotide polymorphism array was used to detect copy-number variants of at least 500 kb in placental or fetal tissue. Variants that were not identified in any of three databases of apparently unaffected persons were then classified into three groups: probably benign, clinical significance unknown, or pathogenic. We compared the results of karyotype and microarray analyses of samples obtained after delivery.

RESULTS

In our analysis of samples from 532 stillbirths, microarray analysis yielded results more often than did karyotype analysis (87.4% vs. 70.5%, P<0.001) and provided better detection of genetic abnormalities (aneuploidy or pathogenic copy-number variants, 8.3% vs. 5.8%; P=0.007). Microarray analysis also identified more genetic abnormalities among 443 antepartum stillbirths (8.8% vs. 6.5%, P=0.02) and 67 stillbirths with congenital anomalies (29.9% vs. 19.4%, P=0.008). As compared with karyotype analysis, microarray analysis provided a relative increase in the diagnosis of genetic abnormalities of 41.9% in all stillbirths, 34.5% in antepartum stillbirths, and 53.8% in stillbirths with anomalies.

CONCLUSIONS

Microarray analysis is more likely than karyotype analysis to provide a genetic diagnosis, primarily because of its success with nonviable tissue, and is especially valuable in analyses of stillbirths with congenital anomalies or in cases in which karyotype results cannot be obtained. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development.).

Differential effects of antiepileptic drugs on neonatal outcomes

Offspring of women with epilepsy (WWE) on AEDs are at increased risks for major congenital malformations and reduced cognition. They may be at risk for other adverse neonatal outcomes. Women with epilepsy on carbamazepine (CBZ), lamotrigine (LTG), phenytoin (PHT), or valproate (VPA) monotherapy were enrolled in a prospective, observational, multicenter study of the neurodevelopmental effects of AEDs. The odds ratio for small for gestational age (SGA) was higher for VPA vs. PHT, VPA vs. LTG, and CBZ vs. PHT. Microcephaly rates were elevated to 12% for all newborns and at 12 months old, but normalized by age 24 months. Reduced Apgar scores occurred more frequently in the VPA and PHT groups at 1 min, but scores were near normal in all groups at 5 min. This study demonstrates increased risks for being born SGA in the VPA and CBZ groups, and transiently reduced Apgar scores in the VPA and PHT groups. Differential risks among the AEDs can help inform decisions about AED selection for women during childbearing years.

Causes of death among stillbirths

CONTEXT

Stillbirth affects 1 in 160 pregnancies in the United States, equal to the number of infant deaths each year. Rates are higher than those of other developed countries and have stagnated over the past decade. There is significant racial disparity in the rate of stillbirth that is unexplained.

OBJECTIVE

To ascertain the causes of stillbirth in a population that is diverse by race/ethnicity and geography.

DESIGN, SETTING, AND PARTICIPANTS

A population-based study from March 2006 to September 2008 with surveillance for all stillbirths at 20 weeks or later in 59 tertiary care and community hospitals in 5 catchment areas defined by state and county boundaries to ensure access to at least 90% of all deliveries. Termination of a live fetus was excluded. Standardized evaluations were performed at delivery.

MAIN OUTCOME MEASURES

Medical history, fetal postmortem and placental pathology, karyotype, other laboratory tests, systematic assignment of causes of death.

RESULTS

Of 663 women with stillbirth enrolled, 500 women consented to complete postmortem examinations of 512 neonates. A probable cause of death was found in 312 stillbirths (60.9%; 95% CI, 56.5%-65.2%) and possible or probable cause in 390 (76.2%; 95% CI, 72.2%-79.8%). The most common causes were obstetric conditions (150 [29.3%; 95% CI, 25.4%-33.5%]), placental abnormalities (121 [23.6%; 95% CI, 20.1%-27.6%]), fetal genetic/structural abnormalities (70 [13.7%; 95% CI, 10.9%-17.0%]), infection (66 [12.9%; 95% CI, 10.2%-16.2%]), umbilical cord abnormalities (53 [10.4%; 95% CI, 7.9%-13.4%]), hypertensive disorders (47 [9.2%; 95% CI, 6.9%-12.1%]), and other maternal medical conditions (40 [7.8%; 95% CI, 5.7%-10.6%]). A higher proportion of stillbirths in non-Hispanic black women compared with non-Hispanic white and Hispanic ones was associated with obstetric complications (43.5% [50] vs 23.7% [85]; difference, 19.8%; 95% CI, 9.7%-29.9%; P < .001) and infections (25.2% [29] vs 7.8% [28]; difference, 17.4%; 95% CI, 9.0%-25.8%; P < .001). Stillbirths occurring intrapartum and early in gestation were more common in non-Hispanic black women. Sources most likely to provide positive information regarding cause of death were placental histology (268 [52.3%; 95% CI, 47.9%-56.7%]), perinatal postmortem examination (161 [31.4%; 95% CI, 27.5%-35.7%]), and karyotype (32 of 357 with definitive results [9%; 95% CI, 6.3%-12.5%]).

CONCLUSIONS

A systematic evaluation led to a probable or possible cause in the majority of stillbirths. Obstetric conditions and placental abnormalities were the most common causes of stillbirth, although the distribution differed by race/ethnicity.

Association between stillbirth and risk factors known at pregnancy confirmation

CONTEXT

Stillbirths account for almost half of US deaths from 20 weeks' gestation to 1 year of life. Most large studies of risk factors for stillbirth use vital statistics with limited data.

OBJECTIVE

To determine the relation between stillbirths and risk factors that could be ascertained at the start of pregnancy, particularly the contribution of these factors to racial disparities.

DESIGN, SETTING, AND PARTICIPANTS

Multisite population-based case-control study conducted between March 2006 and September 2008. Fifty-nine US tertiary care and community hospitals, with access to at least 90% of deliveries within 5 catchment areas defined by state and county lines, enrolled residents with deliveries of 1 or more stillborn fetuses and a representative sample of deliveries of only live-born infants, oversampled for those at less than 32 weeks' gestation and those of African descent.

MAIN OUTCOME MEASURE

Stillbirth.

RESULTS

Analysis included 614 case and 1816 control deliveries. In multivariate analyses, the following factors were independently associated with stillbirth: non-Hispanic black race/ethnicity (23.1% stillbirths, 11.2% live births) (vs non-Hispanic whites; adjusted odds ratio [AOR], 2.12 [95% CI, 1.41-3.20]); previous stillbirth (6.7% stillbirths, 1.4% live births); nulliparity with (10.5% stillbirths, 5.2% live births) and without (34.0% stillbirths, 29.7% live births) previous losses at fewer than 20 weeks' gestation (vs multiparity without stillbirth or previous losses; AOR, 5.91 [95% CI, 3.18-11.00]; AOR, 3.13 [95% CI, 2.06-4.75]; and AOR, 1.98 [95% CI, 1.51-2.60], respectively); diabetes (5.6% stillbirths, 1.6% live births) (vs no diabetes; AOR, 2.50 [95% CI, 1.39-4.48]); maternal age 40 years or older (4.5% stillbirths, 2.1% live births) (vs age 20-34 years; AOR, 2.41 [95% CI, 1.24-4.70]); maternal AB blood type (4.9% stillbirths, 3.0% live births) (vs type O; AOR, 1.96 [95% CI, 1.16-3.30]); history of drug addiction (4.5% stillbirths, 2.1% live births) (vs never use; AOR, 2.08 [95% CI, 1.12-3.88]); smoking during the 3 months prior to pregnancy (<10 cigarettes/d, 10.0% stillbirths, 6.5% live births) (vs none; AOR, 1.55 [95% CI, 1.02-2.35]); obesity/overweight (15.5% stillbirths, 12.4% live births) (vs normal weight; AOR, 1.72 [95% CI, 1.22-2.43]); not living with a partner (25.4% stillbirths, 15.3% live births) (vs married; AOR, 1.62 [95% CI, 1.15-2.27]); and plurality (6.4% stillbirths, 1.9% live births) (vs singleton; AOR, 4.59 [95% CI, 2.63-8.00]). The generalized R(2) was 0.19, explaining little of the variance.

CONCLUSION

Multiple risk factors that would have been known at the time of pregnancy confirmation were associated with stillbirth but accounted for only a small amount of the variance in this outcome.