Conceiving Twins While Taking Clomid

The Odds Are Lower Than You May Think

For every 20 pregnancies conceived with Clomid, only one will result in twins. Clomid, which is a pill taken by mouth to induce ovulation, causes twin pregnancies between 5 and 8 percent of the time. That's fewer than one in 10 pregnancies. Your odds of conceiving triplets (or more) on Clomid is even lower: less than one percent (less than one in 100 pregnancies.)

Fertility drugs have a reputation for causing multiple pregnancies—meaning more than one child is conceived at one time, resulting in twins, triplets, or even more babies. If you're taking Clomid (clomiphene), you may be nervous (or excited) about the prospect of having two or more babies at once. However, those newsworthy high-order multiple stories are more likely with injectable fertility drugs that are used during intrauterine insemination (IUI) or in-vitro fertilization (IVF) treatments.

chances of twins with clomid
Illustration by Alexandra Gordon, Verywell

Why Clomid May Increase the Chance of Multiples

A woman's ovaries contain hundreds of thousands of follicles each containing immature egg cells. Once every month, several follicles begin a process of development. Usually, only one follicle fully develops and releases an egg. This is because once a follicle becomes mature enough on its own, the follicle releases hormones into the bloodstream that signal the body to slow down production of egg-stimulating hormones.

Clomid works by tricking the body into bumping up egg-stimulating hormones, causing the follicles in the ovaries to continue to mature, increasing the likelihood that more than one egg will develop to maturity and be released during ovulation.

Most twins conceived with Clomid will not be identical. During clinical trials of twin pregnancies, one in five were identical twins, while 80 percent of the twin pregnancies were fraternal twins (not identical).

Why aren't they identical? Clomid increases your odds of conceiving twins because your ovaries may ovulate more than one egg: Identical twins come from one egg, not two.

Other Factors That Up the Odds Having Twins

Fertility drugs aren't the only cause of multiple pregnancies. Even without Clomid, your odds of getting pregnant with more than one baby increase depending on factors such as your age, height, weight, and family history.

Using a higher dosage than necessary also may increase the risk of having twins. Ironically, using a higher dosage of Clomid than necessary also may lower the chances you'll get pregnant at all because it can cause cervical mucus to be thicker and harder for sperm to travel through. For that reason, when a doctor prescribes Clomid, she will start with the lowest dose. Only if that dosage doesn't trigger ovulation will she increase it.

Women taking Clomid who do not have trouble ovulating or getting pregnant, as well as women younger than 25, may have an increased risk of getting pregnant with twins while taking Clomid.

How Will I Know If I Got Pregnant With Twins While Taking Clomid?

Symptoms of early pregnancy are no different with twins. Nor are an early positive result on a pregnancy test or having high levels of hCG on a blood test reliable indicators of a twin pregnancy. This means you won't know if you conceived twins until you have an ultrasound. Depending on your health history, your doctor may order one at the six-week mark (two weeks after you miss your period), but this may be too early to detect twins. However, by the eighth week, a twin pregnancy should be visible.

What Should I Expect if I'm Expecting Twins After Clomid?

If you get pregnant with twins after taking Clomid, don't panic. Good prenatal care can reduce the odds of complications, and support from friends and family can help you make the most of this double blessing.

You may or may not need to see a high-risk OB specialist just because you are expecting twins. A twin pregnancy can be followed by a regular OB/GYN. If complications arise, however, your doctor may refer you to a specialist.

There are increased risks for both the mother and baby with a twin pregnancy. Also, if you conceived with Clomid, this likely means you were experiencing infertility. Women with a history of infertility are at risk for preterm labor. For these reasons, your doctor may monitor the pregnancy closer than he might with a singleton.

Your doctor will likely order an ultrasound for the last weeks of the first trimester. This ultrasound will look to confirm whether the twins are sharing a placenta or sharing an amniotic sac.

Twins that share a placenta but have separate sacs are known as monochorionic twins. Monochorionic twins are identical twins and come with higher risks. Up to 70 percent of identical twins share a placenta. Twins that share both a placenta and an amniotic sac are known as monochorionic-monoamniotic. This occurs in less than 1 percent of twin pregnancies and is significantly riskier.

The vast majority of twin pregnancies conceived with Clomid are fraternal twins, which means they will have their own placenta and own sac. However, identical twins can also be conceived with fertility drugs. For this reason, having an early ultrasound to determine if the babies are monochorionic or monoamniotic is important.

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Article Sources
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  1. Mcdonald S, Murphy K, Beyene J, Ohlsson A. Perinatal outcomes of in vitro fertilization twins: a systematic review and meta-analyses. Am J Obstet Gynecol. 2005;193(1):141-52. doi:10.1016/j.ajog.2004.11.064

  2. Drug Bank. Clomifene. Updated January 27, 2020.

  3. Food and Drug Administration (FDA). Clomid. Updated October 2012. Reference ID: 3206435 

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