What kind of endometrium can retain embryos?
Introduction: The endometrium – the “intelligent soil” for embryo implantation. The endometrium is not only a product of the menstrual cycle, but also the first threshold for conception of life. According to global reproductive medicine data, about 30% of Repeated Implantation Failure (RIF) cases are directly related to endometrial tolerance abnormality. As the embryo’s “biological incubator”, an ideal endometrial environment requires the simultaneous fulfillment of three major elements: morphological criteria, molecular signaling pathways, and hemodynamics. In this article, we will analyze the dynamics of the endometrium and reveal how it is a key factor in determining the success or failure of pregnancy. I. Cyclic evolution of the endometrium: precise regulation from shedding to regeneration Histological features: complete shedding of the functional layer, leaving only the basal layer (1-4 mm thick), contraction of the spiral arteries leading to ischemic necrosis.Molecular events:Matrix metalloproteinase (MMP-9) activity peaks and breaks down the extracellular matrix.Interleukin-1β (IL-1β) mediates the inflammatory response and initiates the repair program.Clinical significance: Ultrasound at this stage shows a linear hyperechoic endothelium with a blurred basal-muscular junction. Repeated scraping may damage the basal stem cell nests, resulting in a permanently thin endothelium. Hormonal drive: estrogen (E2) dominates, with concentrations rising from <50 pg/ml to 200-300 pg/ml.Structural changes:5-fold increase in number of glands, change from sparse and short to dense and curved.Interstitial cells proliferate and vascular network density increases by 40%.Thickness progression: timing Average thickness Glandular features early stage(D6-8) 5-7 mm Short straight glands with narrow lumen terminal(D12-14) 9-14 mm Spiralization of glands, pre-secretory preparation Case study: 32 year old Emma (AMH 1.2 ng/ml) successfully achieved a spontaneous pregnancy by elevating her late proliferative endometrium from 6mm to 9mm with transdermal estrogen patches (100 mcg/day). II. Secretory phase (days 15-28): molecular code of the window of tolerance Luteinizing hormone (P4) action:Induces glands to…