Cystic fibrosis has a significant impact on the reproductive system in both men and women, though the effects differ dramatically between the two. Roughly 95% of men with CF are infertile due to a structural issue present from birth, while women with CF can often conceive but face several barriers related to mucus, nutrition, and lung health. Understanding these effects is important for anyone with CF who is thinking about starting a family, because effective options exist for both sexes.
Why Nearly All Men With CF Are Infertile
The most well-known reproductive effect of cystic fibrosis is male infertility, which affects about 95% of men with the condition. The cause is congenital bilateral absence of the vas deferens (CBAVD), meaning the tubes that carry sperm from the testicles to the urethra never fully develop before birth. Men with CF typically produce sperm normally inside the testicles, but the sperm has no way to reach the ejaculate. Semen volume is often very low or absent entirely.
This isn’t a hormonal problem or a consequence of being sick. It’s a direct result of the same faulty protein that causes lung and digestive issues. The CFTR protein plays a role in the development of reproductive ducts during fetal life, and without it functioning properly, the vas deferens fails to form. Because this is a structural absence rather than a blockage, it cannot be reversed later in life.
How CF Reduces Fertility in Women
Women with CF are not infertile in the same categorical way men are, but their fertility is reduced through several overlapping mechanisms. The most important one involves cervical mucus. The same protein dysfunction that thickens mucus in the lungs and digestive tract also makes cervical mucus abnormally thick and dehydrated. This creates a physical barrier that sperm struggle to pass through on the way to the egg. Supporting this theory, women with CF have achieved pregnancies through intrauterine insemination, a procedure that deposits sperm directly past the cervix into the uterus, bypassing the mucus barrier entirely.
Nutritional status plays a role as well. CF causes difficulty absorbing fat and fat-soluble vitamins, which can lead to lower body weight and reduced body fat. When body fat drops below a certain threshold, the hormonal signals that drive ovulation become unreliable. Women with CF who are underweight may have irregular or absent periods, reducing their chances of conceiving in any given month.
Girls with CF also tend to reach puberty later than their peers. On average, the first period arrives about two years later than in the general population. This delay is linked to the nutritional challenges of the disease rather than a direct effect on the ovaries themselves.
Sexual Health Challenges for Women
Beyond fertility, CF can affect sexual comfort in ways that don’t get discussed as often. In one study of women with CF, 78.8% reported a lack of vaginal lubrication as their most frequent sexual difficulty, followed by pain during intercourse at 74.1%. Overall, 93.4% of respondents expressed concern about discomfort or pain during sex. These issues likely stem from the same fluid regulation problems that affect other mucus-producing tissues throughout the body. Chronic coughing, fatigue, and shortness of breath can also make intimacy physically challenging.
Assisted Reproduction for Men With CF
Although men with CF cannot conceive naturally, they can become biological fathers through surgical sperm retrieval combined with in vitro fertilization. The most common approach is microsurgical epididymal sperm aspiration (MESA), where sperm is collected directly from the epididymis, a coiled tube sitting on top of the testicle where sperm is stored. The retrieved sperm is then injected directly into an egg in a lab, a technique called ICSI.
Success rates are encouraging. In one series, about 50% of couples achieved a live birth, and another reported a live birth rate of 62.5% per cycle. However, men with full CF (as opposed to those who only have the missing vas deferens without other CF symptoms) tend to have lower sperm concentrations during retrieval, and about 70% need a backup testicular extraction procedure during the same surgery to obtain enough viable sperm. Despite these added hurdles, the final live birth rates are comparable between the two groups.
Pregnancy Considerations for Women With CF
More women with CF are carrying pregnancies successfully than ever before. In Italy, the number of women with CF in their childbearing years grew by 16.2% between 2016 and 2023, reflecting improved survival and health. Many of these women are now having healthy babies.
Lung function is the most important factor in determining pregnancy safety. Current guidelines generally advise against pregnancy when lung function (measured as FEV1) falls below 60% of predicted values, and consider severe pulmonary hypertension or right-sided heart failure absolute contraindications. Pregnancy increases the body’s demand for oxygen and cardiac output, and lungs that are already significantly compromised may not be able to keep up. Women with lung function above this threshold, good nutritional status, and stable disease typically do well through pregnancy, though they need close monitoring by a team familiar with CF.
Gestational diabetes is also more common in women with CF because of pancreatic damage that impairs insulin production. Nutritional demands increase substantially during pregnancy, which can be difficult for someone who already struggles with calorie absorption.
How Newer Treatments Are Changing the Picture
The introduction of highly effective CFTR modulator therapies has reshaped reproductive planning for people with CF. These medications partially restore the function of the defective protein, leading to dramatic improvements in lung function, weight gain, and overall health. For women, better nutrition and improved mucus hydration appear to be increasing the number of successful pregnancies, though researchers are still quantifying exactly how much fertility improves.
For men, the picture is more complicated. Modulators can improve the function of the prostate and seminal vesicles, potentially increasing ejaculate volume. They also improve general health, which can make the process of surgical sperm retrieval and assisted reproduction easier to undergo. But they do not regenerate the vas deferens. The structural absence is established before birth, and no postnatal treatment has been shown to reverse it. Men with CF who want biological children still need assisted reproduction.
Genetic Counseling and Carrier Screening
Because CF is a recessive genetic condition, a child can only develop it if both parents carry a mutation in the CFTR gene. For a person with CF (who carries two mutations), every child will inherit at least one copy. Whether that child has CF depends entirely on the other parent’s genetics. If the partner is a carrier, there’s a 50% chance the child will have CF. If the partner carries no CFTR mutations, the child will be a carrier but won’t have the disease.
Carrier rates vary by ethnicity. Among Caucasians, roughly 1 in 27 people carry a CFTR mutation. Among Hispanic Americans, the rate is approximately 1 in 48, and among African Americans, about 1 in 79. Expanded carrier screening panels that include more mutations can improve detection rates, especially in non-Caucasian populations where the most common mutations differ. Partner screening is a straightforward blood test and is a standard recommendation for anyone with CF who is planning a family.