Abnormal placental villous maturity and dysregulated glucose metabolism: implications for stillbirth prevention

Placental lesions in stillbirth following the Amsterdam consensus: A systematic review and meta-analysis

Placental disorders remain one of the main causes of stillbirth. However, the lack of standardised nomenclature has significantly limited the clinical utility of placental histology. Following the Amsterdam consensus classification, which now allows proper comparisons of placenta histology across the world, we conducted the first systematic review and meta-analysis (Prospero CRD42023410469) to assess the commonest stillbirth-associated placental lesions worldwide. Eighteen studies with 3082 placentas were included. Maternal vascular malperfusion and fetal vascular malperfusion were the most prevalent placental lesions in stillbirth, and significantly more frequent in stillbirths than livebirths [OR 3.0 (95 % CI 2.0-4.5), p < 0.001 and OR 5.12 (95 % CI 3.09-8.47), p < 0.001, respectively]. However, when adjusting for gestational age, only maternal vascular malperfusion remained significant at term. Better understanding of the pathophysiology underlying placental lesions is needed to inform timely risk assessment and therapeutic interventions capable of reducing placental-related stillbirths.

Characterising delayed villous maturation: A narrative literature review

The normal development of the placenta is vital for fetal growth and a healthy pregnancy outcome. Delayed villous maturation (DVM) is a placental lesion that has been implicated in stillbirth. In DVM, villi do not maturate adequately for their gestational age. DVM is characterised by larger and fewer terminal placental villi, low numbers of syncytial knots, and thicker and fewer vasculosyncytial membranes. DVM is most commonly reported in conjunction with maternal diabetes; however, the occurrence of idiopathic DVM suggests that there may be multiple mechanistic pathways that contribute to DVM. DVM can only be diagnosed through histopathological examination after birth, and there is significant interobserver variability in diagnosis. Establishing objective criteria to distinguish between DVM and healthy placentas is key to increasing the understanding of DVM. Vasculosyncytial membrane count, numbers of syncytial knots and CD15, among others, have been presented as potential diagnostic criteria in the literature. This review aims to compile information on DVM, including the pathophysiology, conditions that have reported associations with DVM and potential markers that could be used as criteria to differentiate between DVM and healthy placentas.

Influence of maternal hyperglycemia on placental capillary distribution

OBJECTIVE

This study was conducted to investigate the distribution of placental villous vessels in pregnant women with different degrees of hyperglycemia.

METHODS

A cross-sectional study was performed using placental samples from 30 pregnant women without diabetes (n=10), with gestational diabetes mellitus (n=10), and with previous diabetes (type 1 and type 2 diabetes; n=10). Maternal glycemic control was evaluated using the glycemic mean and glycated hemoglobin levels. Placental samples were obtained during elective cesarean sections and processed for villous vessel analysis using immunohistochemistry for Von Willebrand factor. Vessels within 10μm of the villus margin were classified as peripheral, and vessels at a distance greater than 10μm were classified as central. The number, area, and perimeter of all vessels were evaluated, and the relationship between vessel area and total area of placental villus was calculated.

RESULTS

Pregnant women with gestational diabetes mellitus and those with previous diabetes had higher glycated hemoglobin levels. The number of vessels was reduced in the villi of the previous Diabetes Group owing to peripheral reduction. Additionally, the area, perimeter, and percentage of peripheral blood were lower in the previous Diabetes Group than in the Non-Diabetic Group.

CONCLUSION

Maternal glycemic levels can modify placental capillary distribution.

Relation between possible under-diagnosed/treated glucose dysmetabolism, delayed villous maturation, and lethal fetal pneumonia

BACKGROUND

Gestational diabetes mellitus (GDM) is a known risk factor for stillbirth (Rosenstein et al., 2012) [1]. Delayed villous maturation (DVM), predominantly seen in term placentas in pregnancies complicated with glucose dysmetabolism, may in part be a consequence of excessive maternal glucose leading to release of fetal insulin and other growth factors that promote excessive placental growth at the expense of villous maturation (Redline, 2012) [2].

CASES

We present three cases of under-diagnosed/treated glucose dysmetabolism in women in their first pregnancies cared for in other hospitals in the United Kingdom (UK) with the fatal fetal/neonatal outcomes and confirmed DVM in the placenta and congenital pneumonia on post-mortem examination in all three cases.

CONCLUSION

This cluster supports a hypothesis that DVM and glucose dysmentabolism may make babies more susceptible to severe perinatal infection. All three cases received the antenatal care in their subsequent pregnancies in our unit and had confirmed glucose dysmetabolism which was treated and resulted in healthy babies.

Stillbirth: prevention and supportive bereavement care

Around half of the two million stillbirths occurring worldwide each year are preventable. This review compiles the most up-to-date evidence to inform stillbirth prevention. Many general maternal health interventions also reduce the risk of stillbirth, for example, antenatal care attendance. This review focuses on specific aspects of care: glucose metabolism, targeted aspirin prophylaxis, clotting and immune disorders, sleep positions, fetal movement monitoring, and preconception and interconception health. In the past few years, covid-19 infection during pregnancy has emerged as a risk factor for stillbirth, particularly among women who were not vaccinated. Alongside prevention, efforts to address stillbirth must include provision of high quality, supportive, and compassionate bereavement care to improve parents' wellbeing. A growing body of evidence suggests beneficial effects for parents who received supportive care and were offered choices such as mode of birth and the option to see and hold their baby. Staff need support to be able to care for parents effectively, yet, studies consistently highlight the scarcity of specific bereavement care training for healthcare providers. Action is urgently needed and is possible. Action must be taken with the evidence available now, in healthcare settings with high or low resources, to reduce stillbirths and improve training and care.