I Switched from Clomid to Letrozole

When I went through my first round of fertility treatments, my doctor put me on Clomid and I got pregnant on the third IUI. The second time around, doc decided to put me on the same regimen since my overall fertility picture remained the same. Of course, I agreed with that. I didnʻt care to do much research into it at the time. But I know it’s a common question in the TTC world. What is the difference between Clomid and Letrozole?

Clomid versus Letrozole: A Side by Side Comparison

Letrozole

• Ovulation Rate
  ~60-76% Per Cycle (in PCOS Studies)

• Live Birth Rate
  ~27.5%

• Clinical Pregnancy Rate
  Statistically higher compared to Letrozole

• Endometrial Thickness
  Thicker and more favorable for implantation

• Multiple Pregnancy Rate
  ~3-4% (Lower than Letrozole)

• Side Effects
  - Fatigue/Drowsiness (especially during 5 days of dosing)
  - Dizziness/Lightheadedness
  - Headaches
  - Joint/Muscle Aches
  - Endometrial Lining Generally Preserved
  - Cervical Mucus unaffected
  - Hot Flashes (Less Common)
  - Temporary Spotting
  - Bone Pain (Rare)

Clomid

• Ovulation Rate
  ~48-55% Per Cycle (in PCOS Studies)

• Live Birth Rate
  ~19.1%

• Clinical Pregnancy Rate
  Lower compared to Letrozole

• Endometrial Thickness
  Tends to be thinner, which may impact implantation

• Multiple Pregnancy Rate
  ~7% (Higher than Letrozole)

• Side Effects
  - Hot Flashes/Night Sweats due to estrogen blocking in the brain.
  - Mood Swings/Irritability/Anxiety
  - Breast Tenderness
  - Headaches (sometimes migraine-like)
  - Nausea/Bloating
  - Thinned Endometrial Lining
  - Cervical Mucus Changes
  - Ovarian Cysts (Less Common)
  - Visual (Eyesight) Disturbances
  - Prolonged Estrogen Receptor Depletion

I read somewhere that you aren’t supposed to take Clomid for more than 6 cycles in a lifetime.

I had no idea there was a limit, so I was naturally very alarmed when I read this. Especially because I was on my sixth cycle this lifetime. (Three the first time, three this time.) This was probably the main reason I wanted to switch.

Turns out, 12+ cycles with Clomid increases your chances of Ovarian Cancer…

I’ll just leave that there and move on.

In addition to that little kernel of knowledge, overall I just felt that my body wasn’t reacting to Clomid the way it once did. For as long as I can remember (well at least since I’ve started noticing), I’ve gotten egg white cervical mucus (EWCM) around ovulation. I’m talking EWCM without fail. And, only looking back on hindsight, I haven’t had EWCM since June, when I first got on Clomid. As we all know, EWCM is crucial in giving sperm the best chance of getting to that egg, so no EWCM is not a good a sign.

I can’t even tell if ovulation is even occurring.

On top of the lack of EWCM, my ovulation cramping disappeared too. Prior to our fertility journey, I was consistently ovulating late - CD 22/23 - since I was still breastfeeding. Prior to my first pregnancy, I ovulated consistently as usual - CD13/14/15. I can’t quite say what ovulation was looking like once we started round two of treatments since I was on birth control a bunch in the beginning.

Since starting Clomid, ovulation has looked like this:

• June
  My LH surge (according to the OPK) was on CD10. However, according to my Oūra ring, I didn’t have a sustained rise in temperature until CD16, which likely means I didn’t ovulate until later.

• July
  Because of my very early LH surge in June, my clinic had me fly up for a scan and IUI on CD11. When I went in for the scan, my follicles were a few days behind being ready, so I was given a trigger shot on July 18th. Although I had the trigger, my temperature didn’t show a rise until a week later, July 25th. Even then, it didn’t seem like I had actually ovulated because I had no symptoms. Furthermore, my period which is usually medium-heavy from Days 1-3, light on Day 4 and then basically non-existent on Day 5, changed. I went from medium Day 1 & 2, to basically nonexistent the remaining days.

• August
  I was so busy in August, I ended up forgetting to take my full dosage of Clomid and was unable to track my ovulation via OPK. So all I really have to go off of is my Oūra Ring which has me ovulating around CD18.

Other reasons I switched to Letrozole…

A girlfriend of mine who also experienced infertility had been prescribed Clomid by her doctor in LA that they would do timed intercourse on. That was to no avail. When she started going to the fertility clinic (same one as me), they switched her over to Letrozole and she got pregnant on her first cycle with IUI. Naturally, this made me wonder if that could happen with me as well.

When I started experiencing shorter periods (July/August) I knew something wasn’t right in my reproductive world. I have never, and I mean never, had period shorter than five days unless my first day or two were extremely, extremely heavy. My last two cycles, however, had me with medium flow and ending by essentially CD3. When I looked into it a little more, ChatGPT noted that my uterine lining could be thinner than usual, causing a shorter period with lighter flow. This made sense because a side effect of Clomid is a thinner uterine lining which does not support implantation.

So, I asked my clinic to switch me over to Letrozole and they agreed.

During my first few rounds of Clomid back in 2022, I still had my monthly EWCM as well as ovulation cramping. And again, I was having normal LH surges around CD14/15. That, coupled with the anecdotal feedback from my girlfriend and the weirdly shorter periods, there has to be something going on and really the only thing I can chalk it up to is the Clomid!

We’ll see how things progress from here!

Hugs & Baby Dust
♥ Jilly