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Placenta previa and placental abruption
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Placenta previa is defined as abnormal placental implantation over the cervical os. There are several variants of this definition. A low-lying placenta occurs when the placenta implants in the lower uterine segment; the placental edge lies near, but not over the cervical os. A low-lying placenta is not considered a category of placenta previa, but it is a form of irregular placentation, which may cause vaginal bleeding when the lower uterine segment develops during labor. When the edge of the placenta lies exactly at the internal cervical os, a marginal placenta previa is present. A complete placenta previa occurs when the internal cervical os is completely covered by the placenta. Clinicians refer to a “central previa” when the center of the placenta is covering the internal os of the cervix (Figs. 1 and 2). The term “partial placenta previa” in which part of the placenta covers the internal os of the cervix is not clinically useful, given the above definitions.
Retained Placenta
Published in Sanjeewa Padumadasa, Malik Goonewardene, Obstetric Emergencies, 2021
After the delivery of the fetus, inadequate myometrial contractions, especially in the placental bed, have been implicated in the pathogenesis of retained placenta. Inadequate myometrial contractions are also observed in preterm deliveries and atonic PPH. Therefore, the risk factors for a retained placenta parallel those for uterine atony (discussed in Chapter 14). While a history of a retained placenta in a previous pregnancy is a risk factor, current infection of the uterus may also predispose to a retained placenta. It has been shown that a retained placenta is associated with pre-eclampsia, stillbirth and delivery of a small for gestational age infant, raising the suspicion of a common pathophysiologic pathway between defective disorders of placentation, poor obstetric outcome and placental retention.
Multiple pregnancy and infertility
Published in Janetta Bensouilah, Pregnancy Loss, 2021
All DZ pregnancies are dichorionic (DC) with two separate placentas. This presents lesser risk than that experienced by the majority of MZ twins. In MZ pregnancies, the fetal membranes may surround one or more of the fetuses and they can have shared or separate placentas. Chorionicity relates to the placentation of the pregnancy, and is determined by the stage at which the zygote divides (seeFigure 3.1). The later this occurs in embryonic development, the greater the potential for problems, as more structures are shared. Around a third of MZ twins establish before the third day after fertilisation, so that two separate blastocysts form and implant with a separate placenta and amniotic sac for each twin. This is known as dichorionic diamniotic placentation. Most of the remaining MZ twins develop after the third day, resulting in monochorionic diamniotic placentation, where a single placenta supports two fetuses but they have separate amniotic sacs. Much more rarely, later cleavage after day nine produces a single amniotic cavity, resulting in monochorionic monoamniotic twins. Monochorionic placentation can also occur in higher-order multiples.
Silver nanoparticles suppress forskolin-induced syncytialization in BeWo cells
Published in Nanotoxicology, 2022
Yuji Sakahashi, Kazuma Higashisaka, Ryo Isaka, Rina Izutani, Jiwon Seo, Atsushi Furuta, Akemi Yamaki-Ushijima, Hirofumi Tsujino, Yuya Haga, Akitoshi Nakashima, Yasuo Tsutsumi
A great many people, regardless of age or gender, readily use products that contain nanoparticles, and all of us may be unintentionally exposed to these materials. It is therefore essential to assess the biological effects of nanoparticles in people, such as pregnant women, who are vulnerable to chemicals. In this regard, we showed previously that a proportion of the nanoparticles to which pregnant mice were exposed could reach the placenta and induce fetal dysgenesis (Yamashita et al. 2011; Higashisaka et al. 2018). However, it remains unclear how nanoparticles affect placentation. The successful establishment of placentation is essential for the maintenance of pregnancy, leading to well-being of fetuses (Nakashima et al. 2021). Given that structural and functional abnormalities of the placenta lead to poor pregnancy outcomes (Wan Masliza et al. 2017; Berceanu et al. 2018), there is a need to understand the effects of nanoparticles on placentation and subsequent pregnancy.
Physiological characterization of an arginine vasopressin rat model of preeclampsia
Published in Systems Biology in Reproductive Medicine, 2022
Sapna Ramdin, Thajasvarie Naicker, Virushka Pillay, Sanil D. Singh, Sooraj Baijnath, Blessing N Mkhwanazi, Nalini Govender
Despite a significant increase in pup numbers in the PAVP vs PS group, the weight per pup was significantly lower in the PAVP in contrast to the PS group. Abnormal placentation characteristic of preeclamptic placentae leads to reduced placental perfusion and hypoxia (Cheng and Wang 2009) with consequent fetal growth restriction (Cotechini et al. 2014). We also demonstrate significantly lower individual placental weights in the PAVP vs the PS groups. The smaller placentae may be associated with reduced uteroplacental blood flow due to vasoconstriction of spiral arterioles, which directly influences fetal growth (Ferrazzani et al. 2011), mirroring human PE. Placental spongiotrophoblasts are responsible for increasing nutrient availability to the placenta in response to the maternal metabolic adjustments to pregnancy (Hu and Cross 2009; Eaton et al. 2020). Our histology data demonstrate that the labyrinth trophoblast cells lining the vascular channels appeared normal with occasional vacuolation while the spongiotrophoblasts were frequently degenerative in the AVP-treated group vs the untreated group. The spongiotrophoblasts were often necrotic, with phagocytic material visible, which correlates with the reduced relative size of the basal/junctional zone. It is possible that AVP-induced necrosis and cellular degeneration leading to decreased spongiotrophoblast proliferation and inadequate placental development on the fetal side, which corresponds to the lower individual pup weights observed in the treated groups (Eaton et al. 2020).
Maternal and neonatal outcomes in the following delivery after previous preterm caesarean breech birth: a national cohort study
Published in Journal of Obstetrics and Gynaecology, 2022
Anna Toijonen, Pia Hinnenberg, Mika Gissler, Seppo Heinonen, Georg Macharey
On the contrary, caesarean section in planned term deliveries is associated with an increased maternal short-term morbidity (Hofmeyr et al. 2015). Having had a planned term caesarean birth compared with planned vaginal birth might also cause in subsequent pregnancies adverse outcomes. Women with at least one previous caesarean section are more likely to have another caesarean (Uddin and Simon 2013). Several studies also indicate that women with a previous caesarean section are more often in need of a blood transfusion. They have an increased risk of endometritis, uterine rupture, hysterectomy, and death (Royal College of Obstetricians and Gynaecologists 2015). Women with a history of caesarean section suffer more often from placenta previa (Jauniaux et al. 2019), and abnormally invasive placentation like placenta accrete (Silver et al. 2006). A history of planned caesarean birth at term increases the risk of stillbirth and neonatal morbidity during subsequent pregnancy (O'neill et al. 2013). For caesarean sections in preterm pregnancies, the risks named above might be even higher, as during a caesarean section, often, an enlarged uterotomy is necessary to deliver the foetus safely. These enlarged incisions are more traumatic compared to the usual lower segment incisions, as the uterus is quite often opened up to the fundus (Figure 1). However, women with a history of preterm caesarean have high rates of successful trial of labour in a subsequent term pregnancy (Rietveld et al. 2019).