Fertility and Immunosuppressants: What You Need to Know Before Trying to Conceive

Trying to get pregnant while on immunosuppressants? Here’s what actually matters.

If you’re taking immunosuppressants for an autoimmune disease or after an organ transplant, and you’re thinking about starting a family, you’re not alone. But you’re also not in the clear. These medications keep your body from attacking itself-or your new kidney, liver, or heart-but they don’t play nice with reproduction. The good news? Many people on these drugs have healthy babies. The catch? It takes planning. Not months. Not weeks. At least six months of careful preparation before even trying to conceive.

Back in 2000, doctors had almost no data on what happened to babies born to parents on immunosuppressants. Today, we know more. We know that some drugs are safe. Others are dangerous. And some? They can permanently damage your ability to have children. The key isn’t avoiding pregnancy-it’s choosing the right time, the right drug, and the right team to guide you.

Which immunosuppressants are safe during pregnancy?

Not all immunosuppressants are created equal. Some have decades of data showing they’re safe for both parent and baby. Others? They’re off-limits.

Azathioprine is the gold standard. Over 1,200 pregnancies have been tracked, and there’s no link to birth defects. It’s the go-to for women with lupus or kidney transplants who want to get pregnant. Many doctors keep patients on it throughout pregnancy because stopping it risks a flare-up-worse than the drug itself.

Corticosteroids like prednisone? They’re generally okay, but not without risk. They can throw off hormone balance, making ovulation unpredictable. They also raise the chance of premature rupture of membranes by 15-20%. Still, most doctors don’t stop them cold. They just lower the dose as much as possible.

Belatacept is newer. Only three pregnancies have been reported so far, and all resulted in healthy babies. That’s promising, but it’s not enough to call it safe. It’s not yet a first choice, but for some, it might be the best option if other drugs aren’t working.

Drugs to avoid before and during pregnancy

These aren’t just risky-they can cause permanent harm.

Cyclophosphamide is one of the worst offenders. For women, it can destroy ovarian reserve. Up to 70% of those who take more than 7 grams per square meter of body surface end up with early menopause. For men, it can wipe out sperm production permanently in 40% of cases. If you’re on this drug and want kids someday, talk to your doctor about freezing eggs or sperm before you start.

Methotrexate is a known embryotoxin. It doesn’t just raise the risk of miscarriage-it can cause severe birth defects. You must stop it at least three months before trying to conceive. And yes, that means waiting. No shortcuts.

Chlorambucil is even more dangerous. It’s linked to kidney missing at birth, heart defects, and ureter problems. The FDA classifies it as Risk Category D-meaning proven harm to humans. If you’re on this, pregnancy is not advised. And if you’re breastfeeding? Forget it. Chlorambucil passes into breast milk.

Sirolimus has a scary track record. In early reports, 43% of pregnancies ended in miscarriage. One baby had a major structural abnormality. It’s still officially contraindicated during pregnancy. Even if your doctor says it’s "probably fine," the data says no.

Sulfasalazine is different. It doesn’t cause birth defects. But it cuts sperm count in half-sometimes by 60%. The good news? It’s reversible. Stop the drug, wait three months, and sperm counts bounce back. Men on this drug should get a semen analysis before trying to conceive.

Men, your fertility matters too

Most people think fertility is a woman’s issue. It’s not. Half the equation is male. And many immunosuppressants affect sperm.

Sulfasalazine, as mentioned, lowers sperm count. So does cyclophosphamide-but that one can be permanent. Other drugs like mycophenolate and tacrolimus? We don’t have enough data. That’s because, for decades, drug makers didn’t test male fertility. The FDA and EMA didn’t require it. So we’re playing catch-up.

Here’s what you should do if you’re a man on immunosuppressants and want kids:

1. Get a baseline semen analysis before starting any new drug.
2. Test again after 74 days (one full sperm cycle) on the drug.
3. If you stop the drug, test again at 13 weeks after stopping.

This isn’t optional. It’s the only way to know if your fertility is at risk-and if it can come back.

Why timing matters more than you think

It’s not enough to just stop a bad drug. You need time for your body to recover.

Methotrexate? Wait three months. Sulfasalazine? Three months. Cyclophosphamide? Even longer-if you’re lucky, your ovaries or testes might recover. But if you’ve hit the dose threshold for permanent damage, no amount of waiting helps.

For transplant patients, stability is key. Your doctor won’t let you try to conceive if your kidney or liver function is unstable. A creatinine level above 13 mg/L before pregnancy? That triples your risk of pre-eclampsia. So you need stable labs, controlled disease, and a drug regimen that won’t trigger rejection.

That’s why preconception counseling isn’t a chat. It’s a full medical review. You need input from your rheumatologist, transplant team, OB-GYN, and fertility specialist. No one person has all the answers.

What happens after your baby is born?

Safe pregnancy doesn’t mean safe parenting.

Babies born to mothers on immunosuppressants often have lower B-cell and T-cell counts. That means a higher risk of infections in the first year. Vaccines might need to be delayed. Fevers? Don’t wait. Call your pediatrician immediately.

Some drugs pass into breast milk. Chlorambucil? Absolutely not. Azathioprine? Probably okay, but monitor the baby for signs of low white blood cell counts. Tacrolimus? Low levels in milk, but still use caution.

There’s no data yet on long-term development-like learning, behavior, or immune health-into childhood. That’s why registries are being built. If you’re part of a pregnancy on these drugs, ask if your hospital is tracking outcomes. Your participation helps the next person.

What’s changed since 2000?

Back then, doctors told women with lupus or kidney disease: "Don’t get pregnant." Now, they say: "Let’s plan it right."

Why? Better drugs. Better monitoring. Better data. We now know that 85% of transplant centers have formal protocols for pregnancy. We know which drugs are safe. We know how to protect fertility before it’s too late.

But we still don’t know everything. Newer drugs like belatacept, voclosporin, or obexelimab? We have maybe 10 years of use. That’s not enough to say they’re safe for babies. The FDA now requires rigorous male fertility testing before approving new drugs-but most of the ones people are on today were approved before those rules existed.

That’s why personalized care matters. Your disease, your drug, your age, your fertility history-none of these are one-size-fits-all.

What to do next

If you’re thinking about having a baby while on immunosuppressants:

• Don’t wait until you’re pregnant to ask questions.
• Ask your doctor: "Which of my medications are safe? Which need to change?"
• Request a fertility evaluation-semen analysis for men, ovarian reserve testing for women.
• Start planning at least six months before trying.
• Find a team: transplant specialist, rheumatologist, high-risk OB, and fertility expert.
• If you’re on cyclophosphamide or chlorambucil, ask about egg or sperm freezing now.

This isn’t about giving up your dream of a family. It’s about protecting it. The science is here. The tools are here. You just need to use them before it’s too late.