IVF Factors

Follicle size, estradiol (E2) levels and endometrium lining

During an IVF cycle, there are three things you want to know after every visit to your clinic: follicle size, the thickness of your uterine (endometrium) lining, and your estradiol level. These are the key data that let you and your doctor know how your cycle is progressing.

Estradiol is measured in either pg/mL (picograms per millilitre) or pmol/L (international measurement).
The conversion factor is E2 (pMol/L) = pg/mL x 3.676.

IVF is all about the eggs and one important indicator of your cycle is follicle size. Follicle size indicates how your eggs are developing and when they will be mature enough for retrieval. Follicles grow approximately 2mm a day on average and produce increasing levels of estradiol.

Estradiol levels also affect the uterine lining, with higher levels correlating to a thicker uterine lining. Uterine lining should measure at least 7 to 8 mm in thickness and usually grows 1-2mm a day.  

Estradiol Levels During In-Vitro Fertilization:  

Just like Goldilocks' porridge, the estradiol level during an IVF cycle needs to be just right. Too high, you're at risk for hyperstimulation. Too low, your response to your doctor's protocol may not be optimal. But what exactly is a good, low, or high estradiol level? How can you judge the progress of an in-vitro fertilization cycle by the estradiol levels?

It's difficult to give exact numbers because every cycle and body is different, but, in general, a 'good' estradiol level is between 150- 500 pg/ml on day eight of an IVF cycle. Approximate doubling of the day eight value every 48 hours is a positive sign of continued follicle development.

hCG is administered when the serum estradiol level reaches 200-600 pg/ml per follicle >17-18 mm in diameter

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