The document discusses factors affecting implantation in cases of thin endometrium, highlighting the oxygen tension theory and estrogen receptor abnormalities. It explains that a functional layer thinner than 7 mm may expose the embryo to high oxygen concentrations due to proximity to spiral arteries, which can hinder implantation. The ideal oxygen tension for embryo implantation is found in a thicker endometrium with lower oxygen levels.

1. Implantation series
By
Dr Pavithra.A
Pharm.D

2. Why doesn’t implantation occur in thin endometrium?
 Oxygen tension theory (OTT)
 Estrogen receptor abnormalities (ERA)
 For the uterine lining to grow estrogen has to bind with estrogen receptor
 If the receptor are abnormal the lining will not grow
 Functional layer of endometrium has plenty of small blood vessels (Capillaries) in contrast to large spiral arteries in
basal layer
 With ovulation there is constriction of spiral arteries with reduced blood flow to functional layer.
 This results in reduced oxygen tension, which is good for embryo implantation.
 If endometrial thickness is <7 mm, it is the functional layer that is thin, & implanting embryo would be much closer to
spiral arteries, higher vascularity & oxygen concentrations.
 High oxygen concentrations near endometrial interface layer could be detrimental compared with usual low oxygen
tension of surface endometrium.