Mechanisms of Disease in Preterm Labor and Complications of Prematurity; Prenatal Diagnosis of Congenital Anomalies
- Roberto Romero, MD, DMedSci, Chief, Pregnancy Research Branch
Preterm birth is the leading cause of perinatal morbidity and mortality worldwide, and two-thirds of all preterm births occur after the onset of preterm labor. The cost of prematurity in the United States alone was estimated at $26 billion per year in 2007. Therefore, important goals are to understand the mechanisms of disease responsible for preterm birth and fetal injury and to improve the prediction and prevention of preterm birth. The Pregnancy Research Branch proposed that preterm parturition is a syndrome caused by multiple pathologic processes [Romero R et al. Science 2014;345:760]. The Branch developed methods for the rapid diagnosis of intra-amniotic infection/inflammation and showed that such pathologic processes can be treated successfully. In addition, the current approach to predict and prevent spontaneous preterm birth in clinical obstetrics is based on the work of the Branch (the PREGNANT trial and subsequent meta-analyses). The research team continues to study the physiology of pregnancy and parturition to inform studies of spontaneous preterm labor, and, in particular, the use of high-dimensional, post-genomic tools, such as transcriptomics, proteomics, and the analysis of parturition at single-cell resolution.
Imaging is a powerful instrument for scientific discovery and has changed the practice of obstetrics and maternal-fetal medicine. The single most important step that has made fetal medicine a discipline is the transformation of the fetus from an invisible to a visible subject through the use of imaging techniques, in particular, ultrasound. The technology has allowed the definition of fetal anatomy, biometry, and growth as well as the study of physiologic parameters, e.g., cardiac function, fetal sleep, and breathing. We use different imaging modalities to examine the diagnosis of anomalies and obstetrical syndromes. Such modalities include ultrasound (2-dimensional, 3-dimensional), magnetic resonance imaging, and optical methods. We have also utilized other imaging techniques to study the human placenta.
A new taxonomy of obstetrical disease based on clinical symptoms and the results of placental pathology
The current taxonomy of obstetrical disease refers to preeclampsia, preterm labor, preterm premature rupture of the membranes, small-for-gestational-age fetus, fetal death, etc. Each complication of pregnancy is named based on symptoms and signs, but this does not provide etiological information. We propose that a new taxonomy of obstetrical syndromes, which incorporates information derived from placental pathology, would facilitate the discovery of biomarkers, which are tools to predict, diagnose, and monitor response to therapy. This study was conducted to examine whether sub-classification of obstetrical syndromes, according to the presence or absence of placental lesions, would improve the performance of biomarkers.
We reported the results of a retrospective case cohort study based on 4,006 pregnant women. The case cohort included 1,499 patients from the parent cohort. Pregnant patients were classified into a control group of patients who delivered at term without pregnancy complications (n=540) and a series of cases including patients with: (1) preterm labor with intact membranes (n=203); (2) preterm PROM (premature rupture of membranes) (n=112); (3) preeclampsia (n=230); and (4) small for gestational age (n=334). Serial samples of maternal plasma were assayed for placental growth factor (PlGF) and the soluble VEGF receptor Flt-1 (7,560 samples). Placentas were examined by pathologists masked to the clinical outcome to assess the presence or absence of lesions reflecting maternal vascular malperfusion. We compared the profile of PlGF and sFlt-1, and its ratio between controls and each obstetrical syndrome with and without subclassification of cases according to the presence or absence of maternal vascular lesions of malperfusion.
We found that: (1) when obstetrical syndromes are classified based on the presence or absence of placental lesions of maternal vascular malperfusion, significant differences in the mean plasma concentrations of PlGF, sFlt-1, and the PlGF/sFlt-1 ratio between cases and controls emerge earlier in gestation; (2) the strength of association between an abnormal PlGF/sFlt-1 ratio and the occurrence of obstetrical syndromes increases when placental lesions of maternal vascular malperfusion are present; and (3) the PlGF/sFlt-1 ratio at 28 to 32 weeks of gestation is abnormal in patients who subsequently delivered as a result of preterm labor with intact membranes and in those with preterm premature rupture of the membranes if both groups have placental lesions of maternal vascular malperfusion. The association is not significant in patients with these obstetrical syndromes who do not have placental lesions. We propose that a new taxonomy of obstetrical disorders informed by placental pathology will facilitate the discovery and implementation of biomarkers, as well as the prediction and prevention of such disorders.
Preeclampsia at term: the identification of two clusters based on angiogenic and anti-angiogenic markers with different clinical characteristics and pregnancy outcomes
Preeclampsia is a major cause of maternal and neonatal death. Most cases of preeclampsia occur at term. An anti-angiogenic state is a mechanism of disease in this syndrome, and maternal plasma concentrations of angiogenic and anti-angiogenic factors such as PlGF and sFlt-1, respectively, have been used for risk assessment (now approved by the FDA). The role of the PlGF/sFLT-1 ratio is mainly in early onset disease. Our study was conducted to determine the prevalence and clinical significance of abnormal angiogenic and anti-angiogenic factors in preeclampsia at term. We found that, while 90% of cases of early preeclampsia had an abnormal angiogenic profile, only 50% of women with preeclampsia at term had such abnormal profile. Patients with preeclampsia at term with an abnormal PlGF/sFLT-1 ratio were more likely to be nulliparous, had a higher rate of maternal and neonatal complications, and were more likely to have placental lesions of malperfusion than those without an abnormal profile. Patients with a normal angiogenic profile have a higher frequency of chronic hypertension and obesity than those with an abnormal profile. These observations have implications for the understanding of preeclampsia at term, prediction of late onset preeclampsia, and its clinical management.
The vaginal microbiota of pregnant women varies with gestational age, maternal age, and parity.
Intra-amniotic infection is a major cause of spontaneous premature labor and delivery, and is present in 25% of spontaneous preterm births. Such infections are largely subclinical in nature and thought to result from microorganisms ascending from the vagina. Changes in the microbial ecosystem or microbiota are believed to predispose to ascending infection. The study was undertaken to characterize the vaginal microbiota of pregnant women who delivered at term without complications, using sequence-based microbiologic techniques (16s). We performed a longitudinal study that included 474 women and 1,862 samples of vaginal fluid from a predominantly African American cohort. Each patient had 3–4 samples collected between 8–38 weeks of gestation. The general pattern was that the composition of the vaginal microbiota remains or transitions to a state of Lactobacillus dominance. We found that the vaginal microbiota changed as a function of gestational age, maternal age, and parity. Network analyses revealed dynamic associations among specific bacterial taxa within the vaginal ecosystem, which shift through the course of pregnancy. The study provides a robust foundational understanding of the vaginal microbiota in pregnancy and lays the groundwork for further investigation of the microbiota prior to spontaneous premature labor.
Fetal intelligent navigation is superior to manual navigation to examine the fetal heart with ultrasound.
Congenital heart disease (CHD) is the most common birth defect by organ system, and the leading cause of infant morbidity and mortality related to birth defects. In 2013, hospital costs exceeded $6 billion to care for children with CHD. All pregnancies should undergo prenatal sonographic screening for cardiac defects, given that up to 90% of cases occur in the absence of risk factors. Moreover, there is evidence that prenatal diagnosis of specific cardiac anomalies improves the survival after surgery, and long-term neurocognitive function and outcome. The overall prenatal detection rate for congenital heart disease with ultrasound remains suboptimal. To address these issues, the PRB successfully developed a novel method known as Fetal Intelligent Navigation Echocardiography (FINE) to interrogate fetal sonographic cardiac volume datasets. The method allows the automatic display of nine standard fetal cardiac views required to diagnose most cardiac defects. The FINE method simplifies examination of the fetal heart and reduces operator dependency. Virtually all ultrasound examinations use manual navigation to examine the fetal heart. We conducted a study to compare the performance of manual and intelligent navigation (FINE) of the fetal heart by non-expert sonologists. This prospective observational study included ten sonologists who underwent formal training on both navigational methods. Subsequently, we tested the ability of participants to obtain nine cardiac views from five STIC (spatiotemporal image correlation) volumes of normal fetal hearts (19–28 gestational weeks) using such methods. The following parameters were determined for both methods: (1) success rate of obtaining nine cardiac views; (2) mean time to obtain nine cardiac views per sonologist; and (3) maximum number of cardiac views successfully obtained for each STIC volume.
All fetal cardiac images were obtained from 100 STIC volumes (50 for each navigational method) and reviewed by an expert in fetal echocardiography. Compared with manual navigation, FINE had a significantly: (1) higher success rate for obtaining eight (excluding the abdomen view) appropriate cardiac views (92–100% vs. 56–88%); (2) shorter mean time (minute:seconds) to obtain nine cardiac views (2:11 ± 0:37 vs. 15:49 ± 7:44); and (3) higher success rate for obtaining all nine cardiac views for a given STIC volume (86% vs. 14%).
We conclude that when performed by non-expert sonologists, intelligent navigation (FINE) had a superior performance than manual navigation of the fetal heart. Specifically, FINE obtained appropriate fetal cardiac views in 92–100% of cases.
Syndecan-1, a biomarker for fetal growth restriction
The identification of fetal growth disorders is an important priority in obstetrics, given that they increase the risk of perinatal morbidity and mortality, as well as adult disease. A subset of small-for-gestational age (SGA) infants are growth-restricted, which is often attributed to placental insufficiency. Syndecan-1, a product of the degradation of the endothelial glycocalyx, has been proposed as a biomarker of endothelial damage in various pathological conditions. During pregnancy, there is a “specialized” form of the glycocalyx, the “syncytiotrophoblast glycocalyx,” which covers the placental villi.
We conducted a study to determine whether maternal plasma syndecan-1 concentrations can be used as a biomarker for fetal growth restriction. A cross-sectional study was performed to include 130 women with normal pregnancy and 50 pregnant women who delivered SGA neonates. Doppler velocimetry of the uterine artery and umbilical artery was performed in women with SGA fetuses at the time of diagnosis. Venipuncture was performed within 48 hours of Doppler velocimetry and plasma concentrations of syndecan-1 were determined by a specific and sensitive immunoassay.
The results showed that the mothers with pregnancies complicated with an SGA fetus had a significantly lower mean plasma concentration of syndecan-1 than those with an appropriate for gestational age fetus. This difference was attributed to fetal growth restriction, as the mean plasma syndecan-1 concentration was significantly lower only in the group of women with SGA fetuses with an abnormal umbilical- and uterine artery–Doppler velocimetry compared with controls. Among women with SGA fetuses, those with abnormal umbilical- and uterine artery–Doppler findings had a significantly lower mean plasma syndecan-1 concentration. A plasma syndecan-1 concentration of less than 850 ng/mL had a positive likelihood ratio of 4.4 and a negative likelihood ratio of 0.24 for the identification of a mother with an SGA fetus with abnormal umbilical artery–Doppler velocimetry. The results of the study suggest that plasma syndecan-1 could be used as a biomarker to identify fetal growth restriction.
Publications
- Motomura K, Romero R, Plazyo O, Garcia-Flores V, Gershater M, Galaz J, Miller D, Gomez-Lopez N. The alarmin S100A12 causes sterile inflammation of the human chorioamniotic membranes as well as preterm birth and neonatal mortality in mice. Biol Reprod 2021 1494–1509.
- Garcia-Flores V, Romero R, Xu Y, Theis KR, Arenas-Hernandez M, Miller D, Peyvandipour A, Bhatti G, Galaz J, Gershater M, Levenson D, Pusod E, Tao L, Kracht D, Florova V, Leng Y, Motomura K, Para R, Faucett M, Hsu CD, Zhang G, Tarca AL, Pique-Regi R, Gomez-Lopez N. Maternal-fetal immune responses in pregnant women infected with SARS-CoV-2. Nat Commun 2022 1–20.
- Pique-Regi R, Romero R, Garcia-Flores V, Peyvandipour A, Tarca AL, Pusod E, Galaz J, Miller D, Bhatti G, Para R, Kanninen T, Hadaya O, Paredes C, Motomura K, Johnson JR, Jung E, Hsu CD, Berry SM, Gomez-Lopez N. A single-cell atlas of the myometrium in human parturition. JCI Insight 2022 1–21.
- Oh KJ, Romero R, Kim HJ, Jung E, Gotsch F, Suksai M, Yoon BH. A role for intraamniotic inflammation in threatened midtrimester miscarriage. Am J Obstet Gynecol 2022 1.e1–1.e13.
- Romero R, Jung E, Chaiworapongsa T, Erez O, Gudicha DW, Kim YM, Kim JS, Kim B, Kusanovic JP, Gotsch F, Taran AB, Yoon BH, Hassan SS, Hsu CD, Chaemsaithong P, Gomez-Lopez N, Yeo L, Kim CJ, Tarca AL. Toward a new taxonomy of obstetrical disease: improved performance of maternal blood biomarkers for the great obstetrical syndromes when classified according to placental pathology. Am J Obstet Gynecol 2022 615.e1–615.e25.
- Purandare N, Kunji Y, Xi Y, Romero R, Gomez-Lopez N, Fribley A, Grossman LI, Aras S. Lipopolysaccharide induces placental mitochondrial dysfunction in murine and human systems by reducing MNRR1 levels via a TLR4-independent pathway. iScience 2022 25:105342.
Collaborators
- Tinnakorn Chaiworapongsa, MD, Wayne State University School of Medicine, Detroit, MI
- Agustin Conde-Agudelo, MD, Wayne State University School of Medicine, Detroit, MI
- Mark Haacke, PhD, Wayne State University School of Medicine, Detroit, MI
- Leonid Margolis, PhD, Section on Intercellular Interactions, NICHD, Bethesda, MD
- Adi L. Tarca, PhD, Wayne State University, Detroit Medical Center, Detroit, MI
- Bo Hyun Yoon, MD, PhD, Seoul National University, Seoul, Korea
Contact
For more information, email romeror@mail.nih.gov.
