Reproductive and Developmental Toxicity
Frank A. Barile in Barile’s Clinical Toxicology, 2019
Exchange of nutrients, gases, and waste material between the maternal and fetal circulations starts from the fifth week after fertilization with the initiation of the formation of the placenta. Maternal and fetal circulations do not mix. Instead, maternal blood enters intervillous spaces (sinuses) of the placenta through ruptured maternal arteries and then drains into uterine veins for return to the maternal circulation. Fetal blood enters the placenta by a pair of umbilical arteries and returns to the fetal circulation by the umbilical vein. The umbilical arteries branch into capillaries surrounded by the syncytial trophoblast, forming the network of chorionic villi. Solutes, gases, and nutrients from the maternal circulation enter the sinuses, surround and bathe chorionic villi, and traverse the epithelium and connective tissues of the villi before penetrating the fetal capillary endothelial cells. Soluble substances are then carried toward the embryo through the umbilical vein.
Abdominal surgery: General principles of access
Mark Davenport, James D. Geiger, Nigel J. Hall, Steven S. Rothenberg in Operative Pediatric Surgery, 2020
Special consideration is required for umbilical access in neonates and infants less than 1 year of age. During fetal circulation, the umbilical vein drains through the ductus venosus into the left hepatic vein, near its junction with the inferior vena cava. After birth, involution of the umbilical vein forms the falciform ligament. However, the age at which the natural patency of the remnant umbilical vein fully closes is not clearly defined. A number of case reports in the medical literature, as well as case law from malpractice lawsuits, document air embolism through the umbilical vein remnant to be a highly morbid or lethal complication of laparoscopy in infants. For this reason, both supraumbilical access and direct access through the center of the umbilicus should absolutely be avoided in neonates and infants. While the vast majority of air embolisms are noted to occur in infants of less than 3 months of age, the timing of full involution of the natural patency is not known. It should also be noted that air embolisms have been documented in cases when insufflation has not yet begun, hypothesized to be secondary to pushing air into the vein during advancement of a sheathed trocar into its Veress needle-placed sheath. Air embolism has also occurred at later stages of a procedure, when a trocar is either intentionally or inadvertently pulled back in the fascia, with resultant insufflation of the umbilical vein. As there is no absolutely safe method to place a trocar near the umbilical vein, it is therefore advised that all neonate and infant trocars be placed in an infraumbilical location.
Fetal echocardiography
Hung N. Winn, Frank A. Chervenak, Roberto Romero in Clinical Maternal-Fetal Medicine Online, 2021
In the normal four-chamber view, the RA and left atrium (LA) are approximately equal in size, and the RV and left ventricle (LV) are also approximately equal in size and thickness, with the RV becoming slightly larger than the LV as gestation progresses (14). The LA is the most posterior cardiac chamber and lies anterior to the descending aorta. The flap of the foramen ovale (septum primum) moves from the RA into LA, billowing about half-way into the LA, consistent with the right-to-left direction of foramen ovale flow in fetal circulation. The RV is the most anterior cardiac chamber and sits just posterior to the sternum. The LV cavity comprises the cardiac apex. The RV can be identified by the moderator band that courses across the lower part of the RV, from the interventricular septum to the RV free wall. The RV is also identified by the tricuspid valve that inserts into it. The atrioventricular valves are slightly offset from each other, with the tricuspid valve attaching slightly more apically than the mitral valve. From the four-chamber view, a posterior sweep will show the coronary sinus, which should be a thin structure that courses within the LA (Fig. 5). A dilated coronary sinus is seen when a persistent left superior vena cava (SVC) or anomalous pulmonary veins are present.
Quantile-specific heritability of serum growth factor concentrations
Published in Growth Factors, 2021
VEGF regulates endothelial cell integrity and activity during embryogenesis. It is essential for optimal trophoblast proliferation, and adequate maternal and fetal circulation during early pregnancy (Almawi et al. 2013). Recurrent spontaneous miscarriages (≥3 unexplained first-trimester pregnancy losses) are associated with reduced VEGF expression and serum concentrations (Almawi et al. 2013). The histogram in Figure 4C from the data presented by Almawi et al. (2013) shows that differences in serum VEGA concentrations between women who repeatedly miscarried and multiparous women was greatest in TT homozygotes of VEGF −460 T/C (rs833061) polymorphisms (−290 ± 37.9 pg/ml), intermediate in TC heterozygotes (−198 ± 30.0 pg/ml), and least in CC homozygotes (−162 ± 25.5 pg/ml, PTT-CC= 0.006). Correspondingly, the difference between TT and CC homozygotes was greater in the multiparous women (379 ± 34.7 pg/ml) in accordance with their higher average VEGA concentrations (527 ± 15.7 pg/m) than in those who repeatedly miscarried (251 ± 29.7 pg/ml), in accordance with their lower VEGA concentrations (265.6 ± 13.1 pg/ml).
Dexamethasone on absent end-diastolic flow in umbilical artery, in growth restricted fetuses from early-onset preeclamptic pregnancies and the perinatal outcome
Published in Annals of Medicine, 2021
Oana Sorina Tica, Andrei Adrian Tica, Doriana Cojocaru, Mihaela Gheonea, Irina Tica, Dragos Ovidiu Alexandru, Victor Cojocaru, Lucian Cristian Petcu, Vlad Iustin Tica
The mechanism of transient restoration from absent (or reversed) EDF to positive EDF in the UA is unknown. It may be mediated by placental corticotrophin-releasing hormone (CRH) [26]. Exogenous administration of corticosteroids decreases maternal hypothalamic CRH secretion but significantly increases placental production [27]. The peptide binds specific CRH-R2 receptors in the placenta and in the umbilical circulation, with increased expression of nitric oxide synthase (NOS), followed by increased nitric oxide (NO) production and intense vasodilatation [28]. The “selective” effect of corticosteroids on umbilical arteries is due to the little (or no) evidence of the presence of CRH-R2 in the utero-placental circulation [29]. However, during the adult disease state (as seen in ESP), in the systemic circulation, steroids can directly and non-transcriptionally activate endothelial NOS (eNOS) and modulate its activity in a high-dose brief-exposure manner [30]. This phenomenon may be responsible for maternal improvement in some cases and can contribute to the improvement of fetal circulation and consecutively, fetal oxygenation. Another suggested mechanism consists of steroid-induced increased expression of membrane K+ channels in the small intravillous arteries, with vasodilation and decreased resistance [31].
Coronary Sinus Defect, Premature Restriction of Foramen Ovale and Cysto-Colic Peritoneal Band
Published in Fetal and Pediatric Pathology, 2023
The foramen ovale, a transitory atrial septum aperture that allows shunting of oxygenated placental blood to the left side of the heart and into systemic fetal circulation, is formed during the fourth week of gestation [10]. In most instances, the foramen ovale closes at birth or within the first three 3months of life [10]. Premature restriction or closure of foramen ovale, first described by Hansmann and Redel [11], is a deleterious condition occurring either as an isolated defect or in association with other congenital and cardiovascular anomalies [10]. As an isolated defect, restricted foramen ovale was identified in 23 cases by Uzun et al [12] who examined 1682 fetuses ultrasonographically, reporting an overall frequency of 1.4% [12]. All the restricted foramen ovale cases except for two were reported alive (21/1682 = 1.24%). Premature restriction or closure of foramen ovale in association with other anomalies was evaluated in an autopsy series by Levy et al [13] who analyzed 1,150 cases of congenital heart disease and found 10 with premature restriction/closure of foramen ovale reporting a frequency of 0.8%. While, Naeye and Blanc [14] reported 12 cases of prenatal narrowing or closure of the foramen ovale in their autopsy series, most other reports are anecdotal [15]. Literature suggests that majority of premature restriction or closure of foramen ovale are associated with hypoplastic left heart syndrome [3].
Related Knowledge Centers
- Breathing
- Fetal Hemoglobin
- Placenta
- Umbilical Artery
- Umbilical Cord
- Umbilical Vein
- Circulatory System
- Blood Vessel
- Hemoglobin Subunit Alpha
- Hbg1