A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

How does preeclampsia predispose to future cardiovascular disease?

Over the last few decades, there has been increasing emphasis on cardiovascular disease in women and study of female-specific cardiovascular risk factors. Hypertension in pregnancy, and specifically preeclampsia, has been identified as one such risk factor. In this review, we explore the epidemiological evidence for preeclampsia as a risk factor for cardiovascular disease. We propose reasons for this association, giving evidence for potential pathways linking preeclampsia with future cardiovascular disease.

Long-term maternal morbidity and mortality associated with ischemic placental disease

Ischemic placental disease can have long-term maternal health implications. In this article, we discuss the three conditions of ischemic placental disease (preeclampsia, fetal growth restriction, and abruption placenta) and its associated long-term maternal morbidity. Retrospective observational studies comparing pregnancies complicated by ischemic placental disease to uncomplicated pregnancies suggest an increased long-term risk of hypertension, cardiovascular death, metabolic syndrome, and cerebrovascular disease. This association is much stronger in women who had an indicated-preterm delivery due to ischemic placental disease. It is important to adequately counsel women who are diagnosed with these conditions about their future health risks. Increased awareness of the potential health risks and multidisciplinary collaboration remains paramount to instituting the appropriate screening and preventative strategies (i.e., behavior modification) for affected women.

Prediction and prevention of ischemic placental disease

Preeclampsia, intrauterine growth restriction (IUGR), and placental abruption are obstetrical conditions that constitute the syndrome of ischemic placental disease or IPD, the leading cause of indicated preterm birth and an important cause of neonatal morbidity and mortality. While the phenotypic manifestations vary significantly for preeclampsia, IUGR, and abruption, these conditions may share a common underlying etiology as evidenced by: (1) shared clinical risk factors, (2) increased recurrence risk across pregnancies as well as increased co-occurrence of IPD conditions within a pregnancy, and (3) findings that suggest the underlying pathophysiologic processes may be similar. IPD is of major clinical importance and accounts for a large proportion of indicated preterm delivery ranging from the periviable to late preterm period. Successful prevention of IPD and resultant preterm delivery could substantially improve neonatal and maternal outcomes. This article will review the following topics: (1) The complicated research literature on aspirin and the prevention of preeclampsia and IUGR. (2) Research evidence on other medical interventions to prevent IPD. (3) New clinical interventions currently under investigations, including statins. (4) Current clinical recommendations for prevention of ischemic placental disease.