Treating cystic fibrosis before birth: Giving newborns a healthier start
March 4, 2026
Whenever a pregnant patient takes medication, we must always ask a few important questions: Is this drug safe for the developing baby? Do the benefits of Mom continuing the medication outweigh the risks of taking it?
In the case of cystic fibrosis (CF), the answers to these questions may be surprisingly positive.
CF is a genetic, inherited lung condition that causes thick mucus to build up in the lungs, pancreas, and other parts of the body, significantly limiting a person’s length and quality of life. Over the past decade, an innovative class of medications called cystic fibrosis transmembrane conductance regulator (CFTR) modulators has helped many people with CF live longer, healthier lives.
While CFTR modulators are not a cure for cystic fibrosis, women with CF who’ve taken the medication for years are gaining confidence in their chances of safely carrying a pregnancy. Now, we’re learning that these medications may also prevent common complications in babies who are diagnosed with CF before birth.
When a pregnant person takes a CFTR modulator, the medication crosses the placenta and reaches the baby. It can also reach the baby after birth through breast milk, giving newborns a potentially life-changing therapy before they’re old enough to take the medication on their own.
Using CFTR modulators to treat CF in unborn babies is not yet approved by the Food and Drug Administration (FDA), and research is ongoing to determine its long-term safety and efficacy. But for some families, the option represents a hope that didn’t exist before.
Science is moving quickly, and UT Southwestern is at the forefront in CF clinical research and care from pregnancy through adulthood. Whether a woman with CF wants to become pregnant or her unborn baby has been diagnosed with the disorder, specialists in the UT Southwestern Adult Cystic Fibrosis Clinic and the maternal-fetal medicine team are combining our expertise to support informed decision-making.
How do CFTR modulators work?
CFTR modulator therapies target the downstream effects of specific gene mutations in the CFTR protein. The most common mutation is the Phe508del mutation, in which the protein improperly folds, gets stuck in the cell, and degrades instead of rising to the surface to function as a normal ion channel. CFTR modulators provide stability to the folding process and functionality of the protein once it is in place.
Because the first CFTR modulator medications were FDA-approved in 2012, there is not yet ample data about the long-term outcomes of their use. To date, many patients have experienced significantly positive effects, such as reduced lung flare-ups and much better respiratory function.
Early case studies have not found complications in babies exposed to CFTR modulators during pregnancy. The impact on lungs and other organ health is not yet known. Clinical trial data and anecdotal case studies gathered to date show promise for these medications in two specific situations:
- The pregnant parent has CF
- A baby is diagnosed with CF before birth, or the parents learn through carrier screening that one or both of them have the gene associated with CF, increasing the chance that their child could have the condition
Potential benefits for babies
For babies diagnosed with CF during pregnancy, clinical case studies suggest potential benefits of exposure to CFTR modulator medication. These include:
- Preventing some serious CF complications at birth, including pancreatic dysfunction and meconium ileus. Meconium ileus is a serious bowel obstruction that occurs in 15%-20% of infants with CF and requires emergency surgery after birth. A published case report describes a mother who did not have CF but took a CFTR modulator during pregnancy after her unborn baby was diagnosed with CF and meconium ileus. The baby did not need emergency surgery once born and had no other major CF-related complications.
- Allowing development of the vas deferens, which is the tube that transports sperm out of the testicles. Nearly all male babies with CF typically do not develop this tube, but in utero CFTR modulator exposure may preserve fertility later in life.
Signs of CF before birth
Ultrasound imaging can reveal some soft markers of cystic fibrosis in pregnancy, including:
- Wider-than-usual intestines, which can signify an obstruction
- Echogenic bowel, which looks brighter than surrounding tissue
- Inability to see the gallbladder
Diagnosing CF in pregnancy requires noninvasive prenatal testing (available at 10 weeks of pregnancy or after), amniocentesis (done after 16 weeks’ gestation), or chorionic villus sampling (done between 11-13 weeks’ gestation).
Cystic fibrosis program
UT Southwestern’s Cystic Fibrosis Clinic is one of the largest in Dallas-Fort Worth, offering coordinated care from a multidisciplinary team.
Future of CFTR modulator therapy in pregnancy
We are standing at the beginning of a new chapter in cystic fibrosis care. For the first time, we may have the potential to change a child’s outcomes in the earliest stages of the disease.
CFTR modulators do not cure cystic fibrosis, and treating unborn babies who have CF with these medications is not yet FDA-approved. More research is needed to understand:
- Which babies may benefit the most.
- The best time during pregnancy to start the medication.
- Long-term effects of the drugs.
- How best to transition CF care after birth.
Maternal and Fetal Outcomes in the Era of Modulators (MAYFLOWERS), a national CF Foundation-sponsored clinical trial co-led by UT Southwestern, is following parents with cystic fibrosis and their babies to understand medication exposure and safety. The study is ongoing, and preliminary data do not suggest a clear sign of harm to babies who are exposed to their mothers’ CFTR modulator medication during pregnancy.
An upcoming study called Prenatal Modulator Treatment to Prevent CF Complications (PROTECT) aims to better understand how CFTR modulators may affect a pregnancy when the parent does not have CF. This study will also collect data to help shape shared clinical guidance for centers that care for these families.
Choices about your cystic fibrosis care during pregnancy – or your baby’s – are complex. They should be made through shared decision-making conversations with a team of specialists including maternal-fetal medicine doctors, CF experts, pediatric teams, and genetic counselors.
UT Southwestern specialists lead groundbreaking cystic fibrosis research and stay on the cutting-edge of clinical advancements to support families living with CF. While there is still much to learn, the amazing progress of the past decade – and the ongoing advancements each year – are giving families a growing sense of hope.
To talk with an expert about cystic fibrosis and pregnancy, make an appointment by calling 214-645-6616 or request an appointment online.
