Structural characteristics of term human fetal membranes prior to labour: identification of an area of altered morphology overlying the cervix

Abstract

Premature rupture of fetal membranes can have serious clinical implications, especially for the initiation of preterm labour and its consequences. To account for this phenomenon many studies have attempted to identify membrane features that may be uniquely associated with the site of rupture. Our previous work has identified an area of the fetal membrane, following spontaneous term birth which exhibits alterations consistent with structural weakness. The aim of this study was to determine if these changes existed prior to labour. In formalin-fixed paraffin-embedded tissue sections an area of the fetal membrane overlying the cervix, termed the 'cervical membranes', was characterized by an increased thickness of the connective tissue layer (215% increase, P < 0.01) and decreased thickness of both the cytotrophoblast (36% reduction, P < 0.01) and decidual layers (64% reduction, P < 0.01) compared to the rest of the membrane. This resulted in the cervical membranes being significantly thinner (P < 0.05) than the rest of the membrane. Similar changes were also detected in frozen sections of fetal membranes. These regional differences have two important implications in that: (i) the cervical membrane may represent a region of structural weakness susceptible to rupture during labour, and (ii) the paracrine relationships between fetal membranes and the myometrium may be qualitatively affected within different regions of the uterus.

Proteomic analysis of human cervicovaginal fluid collected before preterm premature rupture of the fetal membranes

“…Studies have demonstrated that at term, the supracervical site of the fetal membranes (overlying the cervix) has reduced tensile strength and altered morphology of the connective tissues that is consistent with collagen degradation and increased cellular apoptosis (McLaren et al 1999, Moore et al 2006, Reti et al 2007. In this study, IL1ra expression in the CVF was significantly reduced in women 6-23 days before preterm PROM when compared with gestation-matched controls.…”

Endocrine immune interactions in human parturition

“…Careful examination of the fetal membranes from pre-labour specimens obtained at caesarean section has demonstrated that a zone of weakness exists in the region overlying the cervix (McLaren et al, 1999). The features of this zone include a decrease in thickness in comparison to the rest of the fetal membranes, increased MMP-9 and decreased TIMP-3 and also increased poly (ADP-ribose) polymerase -1 (PARP1) cleavage (El Khwad et al, 2005).…”

Weakening and Rupture of Human Fetal Membranes – Biochemistry and Biomechanics

“…Malak and Bell first identified an area of socalled "high morphological change" in the zone of FM overlying the cervix (Malak & Bell, 1994). This distinct para-cervical region has been demonstrated in the FM from both term vaginal and caesarean section deliveries without labor and comprises approximately 2-10% of the total FM surface area (McLaren et al, 1999a;McParland et al, 2003). Bell's group further characterized this area of FM as having increased matrix metalloproteinase (MMP) -9, increased trophoblast apoptosis, differences in the thickness of membrane sub layers, and increased myofibroblasts in this area (McLaren et al, 1999b(McLaren et al, , 2000a(McLaren et al, , 2000bMcParland et al, 2003).…”