Will Clomid Make You Have Twins?

This post was reviewed for medical accuracy by Rosalie Gunson, a Certified Registered Nurse Practitioner specializing in fertility care.

As a twin mom, I get a lot of questions whenever I go out in public with my boys. “Are they natural?” and Do twins run in your family?” are pretty common. Some people actually come right out and ask if I did IVF.

Fertility drugs such as Clomid (clomiphene citrate) and Femara (letrozole) increase the odds that you will produce more than one egg in a cycle, which means a higher chance of fraternal twins. Follicle monitoring can help ensure that you don’t ovulate “too many” eggs.

It’s not surprising that Clomid makes many women ovulate more than one egg, for several reasons:

The whole point of taking medications like Clomid is to stimulate the ovaries to release eggs.
Ovulating more eggs gives you a better chance of getting pregnant at all that cycle. If one egg doesn’t fertilize and implant, maybe another will.
Even if the goal were to release exactly one egg each time, perfectly fine-tuning the medication to achieve that is harder than it sounds.

So it makes sense that most twins conceived with the help of these medications are fraternal (from two eggs) rather than identical (from one egg that split).

Of course, it’s possible to get pregnant with fraternal twins spontaneously, without the aid of medication.

Some women are genetically predisposed to ovulating more than one egg at a time. That’s why fraternal twins run in families on the mother’s side. If your mom or your maternal grandmother had fraternal twins, you’re more likely to have fraternal twins too. (Fraternal twins in your partner’s family have no genetic impact.)
Women are more likely to superovulate as they get older. Remember that 35 is getting old when it comes to your ovaries (lame, I know!).Having said that, though, the overall rate of pregnancy goes down as you get older. A 42-year-old woman may superovulate, but she’s much less likely to conceive than a younger woman due to lower hormone levels.

The Importance of Monitoring

Follicle monitoring, which involves several internal ultrasounds in the lead-up to ovulation, will show how many mature follicles you are producing.

Typically, doctors will want to see one or two follicles in the 18-20mm range at the time of trigger. If the monitoring shows that your follicles are not growing at a satisfactory rate, your doctor may increase your dose.

For more info about internal ultrasounds, check out my post Do Transvaginal Ultrasounds Hurt?

Taking Clomid (or letrozole) without monitoring is a gamble, because you have no idea if the medication is even working. If you’re not responding well, you’ll end up wasting a lot of time and emotional energy on doomed cycles.

On the other hand, you could be responding too well — that is, assuming that you’re not interested in becoming the next Octomom.

In rare cases, over-responding can lead to getting pregnant with higher-order multiples or even ovarian hyperstimulation syndrome (OHSS), which is a serious condition that requires hospitalization.

So why do some women do unmonitored cycles? Some go that route because they can’t afford all the ultrasounds and doctors’ visits involved in monitored cycles. Others live in a remote area hours from the nearest fertility clinic.

Then there are women who do unmonitored cycles because they’re not seeing a doctor at all and bought the medication online without a prescription. That is super risky for a number of reasons, and I absolutely wouldn’t recommend it!

The need for appropriate monitoring is one reason your primary care physician probably won’t feel comfortable prescribing ovulation induction meds. For more on that, see Can Your PCP Prescribe Clomid (and Other Fertility Meds?

Jon and Kate Plus 8: A Cautionary Tale

In the past, imprecise IVF technology led to a lot of well-publicized pregnancies with higher-order multiples (triplets or more). That’s why a lot of people assume that Kate from Jon and Kate Plus 8, the reality show about a family with sextuplets, did IVF. But she didn’t! She took Clomid.

Today, responsible IVF doctors typically won’t transfer more than one or two carefully-chosen embryos. Advances in assisted reproductive technology have made higher-order multiples from IVF much less common than they used to be. (Source: Fertility Treatments and Multiple Births in the United States — New England Journal of Medicine.)

The challenge with ovulating multiple eggs without IVF is that there’s no way to control how many will take. If you ovulate five eggs and they all fertilize and implant, congrats! You’re now pregnant with fraternal quintuplets.

To prevent that from happening, doctors will counsel patients with “too many” mature follicles to cancel the cycle. That means doing nothing — no sex, no IUI — and starting all over again the next month.

Canceling a cycle feels like a depressing waste of time (and money!), but it’s safer than an extremely high-risk pregnancy. Check out my post Why Would a Cycle of Fertility Treatment Get Cancelled? for more.

Going back to Jon and Kate Plus 8, Kate’s doctor apparently refused to do an IUI that cycle because she had over-responded. Kate and Jon decided to go ahead on their own, and she got pregnant with fraternal sextuplets. That wasn’t a likely outcome, but even unlikely scenarios happen to somebody!

So how many follicles is too many? That depends on your history, your doctor’s judgment, and your tolerance of risk. I triggered with three mature follicles (18mm, 19mm, and 20mm).

My doctor supported going forward with that cycle because I was over 30, I’d already done six medicated cycles that failed, and we accepted the chance that we might get multiples. But if she had advised us to cancel, I absolutely would have.

Multiples: Clomid vs. Injectables

So like I said, getting pregnant with multiples from IVF is far less likely than it used to be, back when doctors would transfer far too many embryos at once.

But if you’re doing timed intercourse and/ or IUI instead, what’s the difference between oral meds and injectable meds when it comes to conceiving multiples?

You have a lower chance of conceiving multiples with oral meds (like Clomid and letrozole) than injectable meds (like Gonal-F, Follistim, and Menopur). Injectable medications are more powerful, and they work faster.

Not only are twins more likely with injectable meds, but so are higher-order multiples. One study in the New England Journal of Medicine found that, “All multiple gestations in the clomiphene and letrozole groups were twins, whereas gonadotropin treatment resulted in 24 twin and 10 triplet gestations.” (Citation)

Usually, your doctor wouldn’t suggest moving on to injectables unless you’d already tried several rounds of Clomid and/ or letrozole without success. If you do try injectables, your doctor will probably want you to have frequent ultrasounds to keep tabs on those developing follicles.

See my posts Are Letrozole and Femara the Same Thing? and When to Consider Moving On to Injectable Fertility Meds for more info about these medications.

Keep in mind that any egg can split and create identical twins. It’s possible to ovulate two eggs and conceive triplets or even quads instead of twins! Many triplets are actually identical twins with one fraternal sibling. Don’t say I didn’t warn you!

What About Identical Twins?

So far we’ve discussed fraternal twins — but what about identical twins? Doctors have long believed that identical twins happen randomly, without any rhyme or reason. Nevertheless, some families do have an unusually high number of identical twins. There may be a genetic explanation for identical twins, but researchers are still figuring it out.

So if identical twins are basically a fluke (as far as we know), you’d think that women who do fertility treatment are no more likely to conceive identical twins than anyone else. Right?

Nope! Identical twins occur in only 0.4% of spontaneous pregnancies, but 2-5% of IVF pregnancies. Scientists aren’t sure why this is the case, but it’s a topic for further research.

Conclusion

Yes, taking Clomid (and letrozole) can lead to twins, but as with all elements of pregnancy, the stars would have to align perfectly.

Plenty of women take Clomid and get pregnant with one baby, or don’t get pregnant at all. And lots of women need to take high doses of fertility medications to ovulate even one egg. The only way to know how you’ll respond is to give it a try.

This post was last updated in March 2021.