What Do Estrogen Levels Really Tell Us During IVF
Patient: Dr Malpani, I’ve been doing regular scans and blood tests during my IVF cycle, and I keep hearing about my oestrogen levels and follicle growth. How are these two things related?
Dr. Malpani: Great question — and it's something every IVF patient should understand. During IVF stimulation, each growing follicle produces oestrogen, specifically oestradiol or E2. So as your follicles grow and mature, your oestrogen levels should also rise proportionally.
Patient: So higher oestrogen levels mean more or better follicles?
Dr. Malpani: In general, yes. A mature follicle around 18–20 mm typically produces about 150–200 pg/mL of oestradiol. So, for example, if you have 10 maturing follicles, we’d expect your E2 level to be somewhere around 1500–2000 pg/mL.
Patient: That sounds quite precise. So do you use this to decide when to give the trigger shot?
Dr. Malpani: Absolutely. We monitor E2 to:
- Confirm that your ovaries are responding to stimulation.
- Time the hCG trigger injection for egg maturation.
- And assess the risk of OHSS, especially if E2 rises too quickly.
Patient: But what happens if the oestrogen level doesn’t keep rising?
Dr. Malpani: That’s when we start getting concerned. Sometimes, oestrogen plateaus or even drops, even though ultrasound shows the follicles are growing. That mismatch is a red flag and can point to several possibilities.
Patient: Like what?
Dr. Malpani: It could mean:
- Follicular atresia – where follicles stop functioning and may not contain viable eggs
- Premature luteinisation – where the body starts converting the follicle into a corpus luteum too early
- Suppressed ovarian function, especially in cases with high-dose or prolonged use of GnRH analogues
- Or it could simply be a lab error in hormone measurement, which is why we sometimes repeat the test to confirm.
Patient: So a sudden drop in oestrogen might mean that the eggs are poor quality?
Dr. Malpani: Exactly — or even that the follicle is "empty". That's why we don’t rely only on ultrasound. A follicle might look big and healthy, but if it’s not producing oestrogen, it’s not functioning properly.
Patient: That makes sense. But what if I have low AMH? My doctor said that my ovarian reserve is low, so does the oestrogen still rise the same way?
Dr. Malpani: That’s an excellent point. In low AMH patients, the situation becomes trickier. You might only grow a few follicles — and sometimes they don't produce as much oestrogen as expected. In such cases, E2 levels may rise more slowly or inconsistently, even if the follicle size looks good on the scan.
Patient: So in my case, it might be harder to judge things just by oestrogen?
Dr. Malpani: Precisely. In patients with low AMH, we have to be extra careful. We interpret E2 levels more cautiously and rely on multiple data points: follicle size, hormone trends, and your previous cycle history. It’s more of a nuanced interpretation than a textbook one.
Patient: So both oestrogen and ultrasound are important, but you need to look at them together?
Dr. Malpani: Exactly. Ultrasound shows us the size and number of follicles, while oestrogen tells us about their functional maturity. When both align — that is, rising E2 with growing follicles — that’s a sign of a healthy ovarian response. If E2 is flat or falling while follicles are still growing, it’s time to re-evaluate.
Patient: This is so helpful, Dr Malpani. I used to think oestrogen was just another number — now I understand how critical it is for guiding decisions.