Once fertilized, your growing baby has a finite amount of time to find a home in your womb. This is called the “window of implantation” and is between 6-10 days post ovulation. The endometrium, or lining of the womb, has been preparing for the arrival of your baby from the beginning of the menstrual cycle and its development needs to be highly synchronized with your baby’s for the pregnancy to develop.
The first half of the cycle is all about estrogen, a hormone that allows the regeneration of the endometrium after it has been shed in your period. Blood vessels reform and the lining thickens.
In the middle part of the cycle, ovulation occurs and there is a hormonal shift, with progesterone being the predominant hormone secreted. This increases both the blood flowing to endometrium, and the secretions by the glands on its surface in preparation for the baby’s arrival. The supporting cells are “decidualised” ensuring the growing baby has the fuel it needs to grow in the initial stages of
Fertilisation has been successful and your growing baby is now ready for implantation. At only 5 days old this “blastocyst” (the name given to the nest of cells that your baby is currently) needs to find a home. The endometrium forms “pinopodes”, which are fingerlike projections forming a receptive parking station for the embryo. Your baby is signaling to the endometrium its readiness to implant as it comes close to its surface. If conditions are right, your baby will stick to the parking station and start to settle into the lining where it will call home for the next nine months.
The communication that occurs between a normally developing baby and the endometrium is imperative in a successful implantation. In fact the endometrium is very quick to recognise an abnormally developing baby and its signaling is altered, often preventing implantation. With new genetic technology we are now beginning to understand the importance of our endometrium. With only 70% of early pregnancies successfully implanting, there is a key role, and a new focus on the endometrium in our understanding of implantation.