Similarly, cases in which fetal malignancy metastasizes to the placenta are rare (Reif, 2014). hese are predominantly fetal neuroectodermal tumors, and only one case in the literature describes transplantation of tumor to the maternal uterus (Nath, 1995).
Normal genital-tract flora can colonize and infect the membranes, umbilical cord, and eventually the fetus. Bacteria most commonly ascend after prolonged membrane rupture and during labor to cause infection. Organisms initially infect the chorion and adjacent decidua in the area overlying the internal os. Subsequently, progression leads to full-thickness involvement of the membranes-chorioamnionitis. Organisms often then spread along the chorioamnionic surface to colonize and replicate in amnionic luid. Inlammation of the chorionic plate and of the umbilical cord-unisitis-may follow (Kim, 2015; Redline, 2012).
Most commonly, there is microscopic or occult chorioamnionitis, which is caused by a wide variety of microorganisms. his is frequently cited as a possible explanation for many otherwise unexplained cases of ruptured membranes, preterm labor, or both as discussed in Chapter 42 (p. 810). In some cases, gross infection is characterized by membrane clouding and is sometimes accompanied by a foul odor that depends on bacterial species.
Amnion nodosum is a condition characterized by numerous small, light-tan nodules on the amnion overlying the chorionic plate. hese may be scraped of the fetal surface and contain deposits of fetal squames and fibrin that relect prolonged and severe oligohydramnios (Adeniran, 2007).
Two notable bandlike structures can be formed by the fetal membranes. Of these, amnionic band sequence is an anatomical disruption sequence in which amnion bands tether, constrict, or amputate fetal parts. Amnionic bands commonly cause limb-reduction defects, facial clefts, or encephalocele (Barzilay, 2015; Guzman-Huerta, 2013). Umbilical cord compromise is another sequela (Barros, 2014; Heifetz, 1984b). Severe defects of the spine or ventral wall that accompany amnionic bands suggest a limb-body wall complex, described in Chapter 10 (p. 206).
Clinically, sonography often irst identiies the sequelae of this sequence rather than the bands themselves. As with any fetal anomaly, targeted sonography is indicated. Identiication of a limb-reduction defect, an encephalocele in an atypical location, or an extremity with edema or positional deformity should prompt careful evaluation for amnionic bands.
Management depends on the degree of anatomic deformity.
Fetoscopic laser interruption of the band may be suitable in highly selected antepartum cases Qavadian, 2013; Mathis, 2015).
In contrast, an amnionic sheet is formed by normal amniochorion draped over a preexisting uterine synechia. Generally, these sheets pose little fetal risk, although slightly higher rates of preterm membrane rupture and placental abruption have been described (Korbin, 1998; Nelson, 2010; Tuuli, 2012).