Endometrial Receptivity

Definition - What does Endometrial Receptivity mean?

Endometrial receptivity (ER) is the ability of the inner lining of the uterus (called the endometrium), to be optimally capable of allowing for the implantation of an embryo.

The endometrium should be thick enough to allow an embryo to implant within. Receptivity plays a vital part in initiating a healthy pregnancy


FertilitySmarts explains Endometrial Receptivity

Endometrial receptivity occurs during the implantation window, a period of time during where the endometrium is most receptive to embryo implantation, typically 6-10 days after ovulation. Various factors can make the endometrium less receptive and interfere with embryo implantation:

  • Genetic factors: Any abnormality in the genes that partake in preparing the endometrium for implantation can cause implantation failure.
  • Hormones: Elevated estrogen levels on the day of hCG trigger shot may also have a detrimental effect on endometrial receptivity. The endometrium should be optimally receptive when the embryo is being implanted. This is known as synchrony between the embryo and endometrium. Having said that, fluctuations in estrogen or progesterone levels might trigger asynchrony between the embryo and endometrium. This asynchrony transforms the endometrium from a receptive to a non-receptive state, making the embryo implantation more challenging.
  • Advancing age: A significant decrement in endometrial receptivity is also seen in older women undergoing assisted reproduction, including in vitro fertilization (IVF). The declining levels of the female hormone progesterone may be responsible for this age-related decline in endometrial receptivity as this hormone helps prepare the endometrium for pregnancy.
  • Clomid: Is a medicine used to stimulate the release of eggs from ovaries that can also impact endometrial receptivity.

There are various ways to identify an endometrium that isn't ready to accept an embryo. Molecules released from the endometrial surface can help ascertain endometrial thickness.

A transvaginal ultrasound may also be used as an alternative tool to assess endometrial receptivity. An Endometrial receptivity array (ERA) can also be done to analyze the expression levels of hundreds of genes involved in endometrial receptivity, and thus determine if the endometrium is ready to accept the embryo.

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