Does Crohn's Disease Affect Fertility? The Evidence

Yes, Crohn's disease affects fertility, but by less than most people fear and by more than ulcerative colitis does. In the largest study we found, Swedish women with Crohn's had about a 12% lower chance of giving birth over follow-up than matched women, and Swedish men with Crohn's about 5% lower (Druvefors 2021; Druvefors 2022). Those averages hide most of the story. Fertility is close to normal for many people whose Crohn's is quiet, and the losses pile up in specific groups: women with active inflammation, women with perianal disease, people who have had several operations, and women whose tubes have been caught up in scar tissue.

That last group is where the most bitter Reddit threads come from. In one, a woman of 40 describes learning that her tubes were blocked, probably by adhesions from inflamed bowel, after years of being told only whether her medicines were safe in pregnancy (r/CrohnsDisease). In another, a woman's gynaecologist found her fallopian tubes filled with blood and suspected Crohn's, and several replies come from women with fluid-filled tubes of their own (r/CrohnsDisease). Most fertility pages for IBD talk about medicines and remission. This one is about the routes by which Crohn's specifically, rather than IBD in general, reaches fertility, and what the evidence on each route actually shows. Breastfeeding has its own guide: Crohn's disease and breastfeeding.

If you have ulcerative colitis, the planning side is covered in our guide to planning pregnancy with ulcerative colitis, which owns the medication timetable, remission targets and the UC fertility figures. We link to it rather than repeat it. We built this article from the full text of the 2025 global consensus on pregnancy in IBD, the Swedish, Canadian and Danish registry studies behind it, and seven r/CrohnsDisease threads. Where we say we "could not find" a study, that reflects our searching of PubMed and Europe PMC, not proof that none exists. This is general information, not advice for your situation.

Does Crohn's disease affect fertility? The numbers

Yes, slightly, and the effect is clearer in Crohn's than in UC. The best data come from Sweden, where every person diagnosed with IBD between 1964 and 2014 can be linked to national birth records and compared with people of the same age from the general population.

For women, the study included 8,672 with Crohn's. Their hazard ratio for giving birth, compared with matched women, was 0.88 (95% CI 0.85 to 0.91), compared with 0.96 for UC. By the end of follow-up, women with Crohn's had an average of 1.46 children against 1.62 in matched women, and 30.8% had no children against 26.9%. Fertility improved over the five decades for UC but not for Crohn's. The most striking result concerned women who already had one child when diagnosed: they were much less likely to have a second (odds ratio 0.71) or a third (0.64) than matched women (Druvefors 2021).

For men, the companion study included 8,283 with Crohn's. The hazard ratio for fathering a child was 0.95 (95% CI 0.92 to 0.98), and the authors titled their paper "minor impact" (Druvefors 2022).

A Canadian study from Manitoba, following women from 1992 to 2018, found lower rates of pregnancy (incidence rate ratio 0.85) and live birth (0.83) in Crohn's compared with women without IBD. The hopeful detail is that these differences were significant before 2010 and no longer visible after it (Tandon 2022). The authors do not prove why, but the obvious candidate is better treatment. A Swedish cohort reaching back to 1964 measures, in large part, the Crohn's of an era before biologics.

The 2025 global consensus on pregnancy in IBD reads the same literature the same way. Its text says recent population studies show "slightly decreased fertility in women with IBD, mainly in those with CD and less so or only marginally in females with UC." Its formal statement is cautious: women with IBD "may have decreased fertility" compared with women without IBD, a conditional statement on very low-quality evidence (Mahadevan 2025).

One thing to know when reading the Swedish papers: their abstracts give the average number of children as "births per 1000 person-years", which cannot be right for numbers like 1.52. The tables label the same figures as achieved parity, the average number of children per person. Our UC planning post explains this in more detail; we use the table's meaning here.

Why Crohn's affects fertility more than UC

Because Crohn's can reach the reproductive organs in ways colitis usually cannot. Ulcerative colitis stays in the lining of the colon. Crohn's can involve the full thickness of the bowel wall, anywhere from mouth to anus, and it can form fistulas, abscesses and adhesions. That gives it four separate routes to fertility, each with a different strength of evidence.

The rest of this article takes each route in turn, then turns to men, medicines and IVF.

Active disease is the biggest lever

Inflammation, not the diagnosis itself, is what most clearly lowers fertility, and it is the one factor that treatment changes. The consensus makes this its firmest fertility statement: it recommends, as a strong recommendation, counselling women with IBD that active disease increases the risk of infertility compared with inactive disease (Mahadevan 2025).

The Crohn's figures behind it:

• Canada. Severity was defined as any hospital admission, or any steroid or biologic prescription, in the 180 days before conception. Compared with women in remission, women with severe Crohn's had an adjusted incidence rate ratio of 0.68 (95% CI 0.47 to 0.99) for pregnancy and 0.57 (0.35 to 0.93) for live birth. In UC, the same comparison was not significant (Tandon 2022). Note that this definition counts a biologic prescription as a sign of severe disease, so it cannot separate the disease from the treatment for it.
• Sweden. Hospital admissions were used as a marker of severe flares. In Crohn's, fertility was not clearly reduced after a first or second admission (hazard ratios 0.96 and 0.93, not significant), but it was after a third (0.88) and after more than three (0.83) (Druvefors 2021).

Why would inflammation matter? There are several plausible routes and no single proven one. Being unwell lowers libido and the frequency of sex, and pain, diarrhoea and fatigue do not help. Weight loss and poor nutrition can disrupt ovulation, and the consensus checklist includes a nutritional assessment before conception for that reason. The commenter on Reddit whose wife only conceived once her albumin, a blood marker of nutrition, came back into the normal range was describing their own experience, not a proven mechanism, but it is a common shape of story in the threads (r/CrohnsDisease).

What about egg reserve?

Studies of ovarian reserve in Crohn's disagree, and the one finding that repeats is that active disease and age matter. Ovarian reserve is usually estimated with anti-Müllerian hormone (AMH), a blood test reflecting how many follicles remain.

• A Turkish study of 50 women with Crohn's and 95 controls found lower AMH in Crohn's (2.1 versus 3.3), smaller ovaries and fewer antral follicles, and lower AMH in active disease than in remission (Kadirogullari 2021).
• A Slovak study of 50 women with Crohn's, all in clinical remission, and 56 controls found no difference in AMH (median 2.6 versus 2.1) or in the share with low reserve. Age was the only independent predictor. Women who had surgery, and those over 30 with Crohn's for more than five years, showed a steeper age-related fall (Koller 2021).

The consensus summarises this literature as small, conflicting and mostly from Crohn's, and says the only factors consistently linked with reduced reserve are age over 30 and active disease. It also says AMH "cannot predict fertility" and should only be used when assessing for assisted reproduction (Mahadevan 2025). So an AMH test ordered out of worry is not a fertility forecast, and a normal one is not a guarantee.

Perianal disease: a clear signal in women, almost none in men

Perianal Crohn's is linked with noticeably lower fertility in women, and the likeliest reason is its effect on sex and pelvic tissue. In the Swedish women's study, perianal disease (anal fistula, abscess or fissure) lowered the hazard ratio for giving birth to 0.75 (95% CI 0.69 to 0.82), against 0.90 in women with Crohn's but no perianal disease (Druvefors 2021). In men, using the same registry and the same definitions, perianal disease made almost no difference: 0.93 (0.86 to 1.00) with it and 0.95 without (Druvefors 2022).

That contrast is useful, because it suggests the mechanism is not just "sicker people have fewer children". If perianal disease only marked severity, it would lower fertility in men too. Something about perianal disease seems to matter more for women, and the sexual function studies point in a plausible direction:

• A French study of 97 people with active perianal Crohn's found sexual dysfunction in 66% of women against 50% of controls. The strongest predictor in women was severely active perianal disease (odds ratio 13.05). In men, 30% versus 16% had sexual dysfunction, a difference the study was too small to confirm (Boudiaf 2021).
• A Dutch study across 41 hospitals found sexual dysfunction in 69% of 211 people with active perianal fistulising Crohn's, 75% of women and 63% of men. Having a partner was protective. Its quality-of-life questionnaires barely tracked sexual function, which is why the authors recommend asking about sex directly rather than assuming a general questionnaire will pick it up (Bak 2026).

Neither study measured fertility, so the link is an inference: pain, fistula drainage and fear of pain make regular sex harder, and the pelvic tissue around a fistula is inflamed. It is not proof. What it does give you is a concrete thing to raise. If sex is painful or avoided because of perianal disease, that is a fertility issue as well as a quality-of-life one, and it is treatable territory for a colorectal surgeon, gynaecologist or sexual health specialist.

There is a wider point in a New Zealand study of 159 people with IBD. Objective measures of inflammation (endoscopy and biomarkers) were not associated with sexual dysfunction. Symptoms were, in women, and so was severe depression in women and severe anxiety in men. Sexual dysfunction was reported by 36 of 59 sexually active women (Mules 2023). How you feel, physically and mentally, may matter more for your sex life than what your calprotectin says.

Can Crohn's block your fallopian tubes?

It can contribute, but nobody has measured how often, and you should be wary of any page that gives a number. This is the route the threads keep returning to and the one fertility guides for IBD mostly skip.

The biological case is straightforward. Crohn's most often affects the end of the small bowel, which sits in the lower right abdomen close to the right ovary and fallopian tube. Transmural inflammation, abscesses and operations all leave adhesions, bands of scar tissue that can stick bowel to pelvic organs. A tube that is kinked, blocked or fluid-filled (a hydrosalpinx) works poorly. In the threads, women describe a gynaecologist suspecting Crohn's after finding a blocked or fluid-filled tube, and being told that inflamed bowel can cause adhesions whether or not there has been surgery (r/CrohnsDisease; r/CrohnsDisease). One commenter who had planned a pregnancy for years with an IBD and high-risk obstetric team wrote that adhesions to the outside of the uterus or tubes were imaged for, but that blocked tubes had never been raised as a risk.

What we could find:

• Ectopic pregnancy, a marker of tubal damage, is slightly more common in Crohn's. A Danish study of 6,731 pregnancies in women with Crohn's found an odds ratio of 1.23 (95% CI 1.01 to 1.49) compared with women without IBD, after adjusting for pelvic and abdominal surgery. Women with UC showed no increase (0.98). Previous IBD surgery raised the estimate further in Crohn's (1.49), though not significantly (de Silva 2018).
• The nearest analogy comes from appendicitis, not Crohn's. In a classic US study of women with tubal infertility, a simple appendectomy carried no excess risk, but surgery for a ruptured appendix carried a relative risk of 4.8 in women who had never been pregnant (Mueller 1986). A later meta-analysis of seven studies found no overall link between appendectomy and infertility (odds ratio 1.03), while noting that complicated appendicitis still pointed toward harm, and found a raised risk of ectopic pregnancy (1.78) (Elraiyah 2014). The lesson that transfers is that pelvic infection and peritonitis, not a tidy operation, are what threaten tubes. That is an inference about Crohn's abscesses and perforations, not a measured result.
• We could not find any study reporting the rate of tubal infertility or hydrosalpinx in women with Crohn's. Case material exists, and UK charity booklets mention scarring around the tubes and ovaries after pelvic surgery, but there is no denominator.

If tubes are the problem, it changes the plan. Blocked tubes are one of the situations where IVF bypasses the obstacle entirely, which is why a commenter who suggested IVF to the woman with blocked tubes was broadly right, provided tubes are the only problem. A hydrosalpinx is a special case, because the fluid itself seems to lower IVF success. A Cochrane review of 11 trials found that removing the affected tube before IVF probably raises the clinical pregnancy rate (risk ratio 2.02, moderate-quality evidence), though no trial of that comparison reported live births (Melo 2020). For someone with Crohn's, more pelvic surgery carries its own adhesion risk, so this is a decision for a fertility specialist and colorectal surgeon together.

Does bowel surgery for Crohn's affect fertility?

Repeated surgery does. A single resection, on the best data we have, mostly does not. This is a finding most pages flatten into "surgery lowers fertility", and the detail is worth having if you are facing an operation.

In the Swedish women's study, 45.1% of women with Crohn's had bowel surgery during follow-up. Compared with matched women, the hazard ratio for giving birth was 0.91 for women with Crohn's and no abdominal operations, 0.95 after one or two (not significantly different from matched women), and 0.69 after three to five (Druvefors 2021). The Canadian study also found that previous IBD surgery did not significantly lower pregnancy rates in Crohn's (adjusted IRR 0.84, 95% CI 0.68 to 1.02), although a j-pouch did in UC (Tandon 2022).

Two cautions. Surgery is partly a marker of severe disease, so a study cannot fully separate the operation from the illness that led to it; the authors of the men's study make exactly this point (Druvefors 2022). And these are averages across whatever operations Swedish surgeons performed between 1964 and 2014, much of it open surgery. The consensus says the mechanism of fertility loss after surgery is thought to be adhesions, and that laparoscopic surgery may carry less risk, but its data on that are sparse and come from UC pouch surgery (Mahadevan 2025).

If you are weighing an operation, our guide to how you know if you need a colectomy covers the decision itself. For fertility, the fair summary is that a well-timed operation that settles uncontrolled disease may help more than it harms, and that the case for raising family plans with the surgeon beforehand is strongest when a pelvic dissection or repeated surgery is on the table.

IVF with Crohn's disease

IVF works for many women with Crohn's, but previous Crohn's surgery lowers the odds, which is an argument for earlier referral. The data come mostly from Denmark, where every IVF cycle is registered:

• In a study of first-time assisted reproduction, the adjusted odds ratio of a live birth within 18 months was 0.58 (95% CI 0.32 to 1.03) for 158 women with Crohn's compared with women without IBD, not quite significant. Among women with Crohn's, those who had previous Crohn's surgery had an odds ratio of 0.29 (0.13 to 0.65) compared with those who had not (Friedman 2017).
• Counting each embryo transfer, the odds ratio of a live birth for women with Crohn's was 0.77 (0.52 to 1.14), not significant overall, but previous Crohn's surgery lowered it to 0.51 (0.29 to 0.91). The authors concluded that women with Crohn's "may seek to initiate ART treatment before needing CD surgery" (Nørgård 2016).
• A meta-analysis found live birth rates per IVF cycle were not reduced in medically managed Crohn's but were 49% to 71% lower after Crohn's-related surgery (Laube 2021).

There are some general reassurances in the consensus. Most maintenance medicines can, in the authors' common practice, continue through egg retrieval, and the consensus states plainly that there are no published data on flares during egg harvesting (Mahadevan 2025). Reddit questions about timing an infusion around an embryo transfer are common, and the honest answer is that this is a coordination question for your IBD and fertility teams, not something with a published rule (r/CrohnsDisease).

Does Crohn's disease affect fertility in men?

Very little on average, but active disease, some medicines and pelvic surgery can matter. This is the most under-served part of the question online, so here is what the studies actually measured.

• Births. Swedish men with Crohn's had a hazard ratio for fathering a child of 0.95. Within the Crohn's group, in the small part of the cohort with prescription data, more intensive medical treatment, used as a marker of severity, was linked with lower fertility (Druvefors 2022).
• Semen during a flare. A Danish study of 20 men admitted with severe active IBD found progressive sperm motility rose from 28.4% during the flare to 37.4% in remission, and testosterone was low during the flare and normalised after. Sperm concentration, shape and DNA fragmentation did not change significantly (Grosen 2019). That last point matters for a Reddit question about inflammation and sperm DNA fragmentation (r/CrohnsDisease): in this small study, severe IBD did not raise it.
• Crohn's versus UC. A Spanish study found men with Crohn's had lower sperm concentrations than men with UC (median 34.5 versus 70) and lower seminal zinc. Sexual function in men in clinical remission was no different from controls (Valer 2017).
• Erections. A meta-analysis of 14 studies estimated erectile dysfunction in 27% of men with IBD, with higher odds after surgery (1.28), with active disease (2.06) and with depression (3.31). The included studies varied a lot (Wu 2022). UK charity material also notes that pelvic operations such as proctectomy can cause erection and ejaculation problems, which often improve with time or treatment.

Is it the disease or the medicine, for men?

For most IBD medicines, the evidence points to the disease, not the drug. Three medicines come up most:

• Sulfasalazine. The one with clear evidence. It lowers sperm count and motility and increases abnormal forms, and the effect reversed after stopping, with 15 pregnancies at a median of 2.5 months afterwards in the original study (O'Moráin 1984). It is an older drug, more often used in UC.
• Anti-TNF drugs (infliximab, adalimumab). Men starting anti-TNF therapy had a small fall in DNA fragmentation that the authors called clinically irrelevant, other semen measures were unaffected, and the drugs appeared in semen only in negligible amounts (Grosen 2019). In the Spanish study, men with Crohn's on anti-TNF drugs had better motility and morphology than those not on them (Valer 2017).
• Methotrexate. Used more in Crohn's than in UC, and the one men most often ask about. A Danish registry study of 193 children whose fathers took methotrexate in the three months before conception found no clear increase in congenital anomalies (adjusted odds ratio 1.10), preterm birth or small size for gestational age (Winter 2017). A 2025 meta-analysis also found no increased risk of malformations (adjusted odds ratio 1.00), stillbirth or preterm birth after paternal exposure (Uysal 2025). Those studies are about the baby's safety, not about sperm count, and the advice given to individual men still varies between clinics. One Reddit poster describes waiting a year to try because of methotrexate before the couple conceived (r/CrohnsDisease).

None of this is a reason to stop or change a medicine on your own. Stopping a drug that keeps Crohn's quiet risks a flare, and a flare is itself one of the clearest threats to fertility.

Is it the disease or the medication, for women?

Mostly the disease. For women, the 2025 consensus recommends that most maintenance medicines continue through conception and pregnancy, because uncontrolled disease is the bigger danger to fertility and to the pregnancy. Its preconception checklist names methotrexate as the main exception, to be stopped at least a month before conception, and sets out stop windows for the small-molecule drugs (Mahadevan 2025). Our UC pregnancy planning guide walks through that medicine table, which applies to Crohn's too. A Reddit poster whose doctor told her to come off infliximab for six months before trying got several replies saying that did not match current practice, which is consistent with the consensus, but the only place to resolve it is a conversation with your IBD team or a maternal-fetal medicine specialist (r/CrohnsDisease).

Two parts of the checklist are particularly relevant to Crohn's. It asks for remission confirmed objectively, including by intestinal ultrasound, MRI or CT where needed, which matters because small-bowel Crohn's can be invisible to a colonoscopy. And it asks for a higher folic acid intake before conception in people with extensive small-bowel disease or malabsorption, at an amount your team will set (Mahadevan 2025).

Some of the gap is choice

People with Crohn's have fewer children partly because they decide to. The first study of this surveyed 169 women with IBD in Illinois: 18% of those with Crohn's were voluntarily childless, against 6.2% in the general population, while rates of involuntary childlessness were similar to the general population (Marri 2007). The Swedish study found women with IBD used contraception more often than matched women, both before and after diagnosis, and its authors concluded that some results "suggest a role of voluntarily reduced fertility" (Druvefors 2021).

The longest thread behind this article is a 21-year-old asking whether Crohn's will make motherhood hard (r/CrohnsDisease). The replies split. Some people describe conceiving quickly in remission and calm pregnancies. Others describe deciding against biological children, because of how severe their disease has been or because of the risk of passing it on. Both are legitimate. What is worth avoiding is a decision built on a belief that Crohn's makes pregnancy impossible, or that every medicine is dangerous, because neither is true.

Will my child get Crohn's disease?

Most children of a parent with Crohn's will not develop it, but the risk is raised, and estimates disagree. A Danish national study found the offspring of parents with Crohn's had 12.8 times the expected rate of Crohn's and 4.0 times the expected rate of UC (Orholm 1999). Those are relative figures; on a low background rate, most children are still unaffected.

The absolute figures are where sources differ. The 2025 consensus cites a 9.2% risk of IBD in offspring if a parent had Crohn's, attributed to that Danish study (Mahadevan 2025). The Danish abstract we read reports only the relative ratios, so we could not check the 9.2% against it. UK patient material from Crohn's & Colitis UK says up to 5 in every 100 children might develop IBD if one parent has Crohn's, and up to 30 in 100 if both parents have IBD. We cannot reconcile 5% and 9.2% from what we read; different populations, time periods and follow-up lengths are the likely reasons. Either way, the risk is real but most children of a parent with Crohn's will not develop it.

How long to try before asking for help

Sooner than you might think: the consensus checklist suggests a fertility specialist review after 6 months of timed intercourse without a pregnancy (Mahadevan 2025). Remission is not guaranteed to last, so it is reasonable not to spend much of it waiting.

A few things from the threads are worth carrying into that appointment:

• Both partners get assessed. In one thread, a couple facing two years of unexplained infertility had a male partner with Crohn's; in another, the woman with Crohn's was the one with the problem (r/CrohnsDisease; r/CrohnsDisease). A semen analysis is a cheap early test.
• Say what your Crohn's has done in your pelvis. Abscesses, fistulas, perforations and every operation belong in the history you give a fertility clinic, because they change how likely tubal damage is and which tests come first. Tubal assessment usually involves imaging of the tubes, which your fertility specialist decides on.
• Bring your IBD team in. A fertility clinic may not know which medicines continue, and an IBD team may not think about tubes. The threads are full of people who felt each specialist saw only their own organ (r/CrohnsDisease). Asking each to write to the other closes that gap. Our questions to ask your doctor about Crohn's disease can help you frame it.

A worked example: two people, one diagnosis

The same diagnosis can carry very different fertility pictures, and the difference is mostly in the details above. These two are illustrative composites, not real patients.

Person A is 29 with ileal Crohn's, diagnosed at 24, in remission on a biologic for two years with a normal calprotectin and a clear MRI, no perianal disease and no surgery. On the evidence, A's fertility is likely close to normal. The useful steps are a preconception visit, keeping the medicine going as the team advises, and asking for help at six months rather than twelve if nothing happens.

Person B is 33 with ileocolonic and perianal Crohn's, two abscesses drained, one ileocaecal resection and a second planned, with sex often painful. B sits in several of the groups where the studies found lower fertility: perianal disease, possible pelvic adhesions, repeated surgery, and an age at which reserve starts to fall. That does not mean B cannot conceive. It does mean B has good reasons to raise family plans before the second operation, to ask whether fertility assessment or IVF should come earlier, and to bring the pain with sex into the conversation as a medical issue.

What to track before and while trying

The most useful record is the one that shows your Crohn's is quiet, plus the history a fertility clinic will ask for. In practice that means:

• A disease activity score over time. The Harvey-Bradshaw Index is the short symptom score Crohn's clinics use. Tracking it weekly gives you a trend to show at a preconception visit. You can work out a score with our free calculator below.
• Test results with dates: calprotectin, CRP, haemoglobin, albumin and imaging.
• Your surgical and perianal history: each operation, abscess and fistula, with dates. People rarely have this written down, and fertility clinics need it.
• Medicines with start and stop dates, including steroid courses, since a steroid course is itself a sign that disease was active.
• Sexual pain or avoidance, noted plainly, so it gets raised rather than skipped.

If you use an app, Clairop calculates the Harvey-Bradshaw Index from symptoms you log and produces a one-page report with the score trend, labs and medication adherence to bring to an appointment (how Clairop works). A notebook does the same job. For a fuller list of what is worth recording, see what to track in an IBD symptom diary, and for what activity actually looks like, our guide to telling whether you are in a Crohn's flare.

Myths about Crohn's and fertility

"Crohn's makes you infertile." It does not, for most people. Swedish women with Crohn's averaged 1.46 children against 1.62, and involuntary childlessness in the Illinois survey was similar to the general population (Druvefors 2021; Marri 2007).

"If you are in remission, Crohn's cannot affect your fertility." Mostly true, but not completely. Adhesions from past abscesses or surgery do not go away when inflammation does, and a tube damaged years ago stays damaged.

"You have to come off your biologic before trying." For most maintenance biologics, the 2025 consensus says the opposite (Mahadevan 2025). Specific advice for you comes from your team.

"Any surgery wrecks fertility." In Crohn's, one or two abdominal operations were not clearly linked with lower fertility in Sweden; repeated surgery was (Druvefors 2021).

"Men with Crohn's should worry about their sperm." On average, the effect on male fertility is small. Sulfasalazine and severe flares are the documented problems, and both are reversible (O'Moráin 1984; Grosen 2019).

"An AMH test will tell you how fertile you are." The consensus says AMH cannot predict fertility and belongs in assisted reproduction assessments (Mahadevan 2025).

When to see a doctor promptly

Contact your IBD team or GP soon, or get urgent care where stated, if:

• You could be pregnant and have sudden one-sided pelvic pain, shoulder-tip pain, fainting or bleeding. Treat this as possible ectopic pregnancy and get urgent care.
• You have fever, a painful swelling near the anus, or new discharge, which can mean an abscess or fistula.
• You have blood in your stool, unexplained weight loss, night-time symptoms or signs of anaemia, such as breathlessness or unusual tiredness.
• You have new pelvic pain with fever or a foul vaginal discharge, or anything passing from the vagina that looks like stool or gas, which can mean a fistula.
• You have been trying for 6 months without a pregnancy, per the consensus checklist, or sooner if you already know of tubal damage, perianal disease or repeated surgery.
• You become pregnant unexpectedly while taking methotrexate or a small-molecule drug. Contact your team promptly rather than stopping anything on your own.

If pregnancy is already under way, the course of IBD during pregnancy is covered in our article on IBD flares during pregnancy, which includes Crohn's figures.

The honest bottom line

Crohn's disease does affect fertility, more than ulcerative colitis and much more in some people than in others. For a woman in remission without perianal disease or repeated surgery, the evidence suggests fertility close to normal, and the gap in pregnancy rates seen in older data had closed in one Canadian study after 2010. The risk concentrates in active disease, perianal disease, multiple operations and tubal damage, and the last of these is the one nobody has counted. For men, the effect is small and mostly reversible.

The practical message is to treat fertility as part of your Crohn's care rather than something to raise only once you start trying: get into objectively confirmed remission, tell both your IBD team and any fertility clinic the full history of what Crohn's has done in your abdomen and pelvis, raise family plans before any operation, and ask for help at six months rather than waiting a year.