When you're pregnant, you get used to asking your doctor (or the Internet) about basically every medication that goes into your mouth, including antibiotics. With all of the warnings and precautions it can feel like you need to avoid all medication during pregnancy, but that's not always possible—especially if you wind up with something like a urinary tract infection (UTI).

Unfortunately UTIs aren't uncommon during pregnancy, and if left untreated UTIs can cause serious issues such as preterm labor, low birth weight, and sepsis, a life-threatening form of infection.

Clearly, it’s important to be treated for a UTI during pregnancy, but a recent report from the CDC found that some pregnant women are still being prescribed antibiotics that have been linked to birth defects.

In the report, the CDC looked at antibiotic prescriptions filled by pregnant women with UTIs in 2014. They analyzed data from the Truven Health MarketScan Commercial Database for pregnancies that occurred during 2014, which included data for 482,917 patients. Of those patients, 7.2 percent were diagnosed with a UTI (40 percent of which occurred during the first trimester). And, of those patients, nearly 35 percent filled a prescription for nitrofurantoin and nearly 8 percent filled a prescription for trimethoprim-sulfamethoxazole, per the CDC data.

Nitrofurantoin (brand name Furadantin or Macrodantin) is an antibiotic primarily used to treat UTIs caused by Escherichia coli, Staphylococcus aureus, Enterobacter species, S saprophyticus, and Klebsiella species, Medscape explains. Trimethoprim-sulfamethoxazole is a combination of two antibiotics that is used to treat a wider variety of illnesses, including ear infections and bronchitis in addition to UTIs. According to Medscape, it's most effective when used to treat UTIs caused by Escherichia coli, Enterobacter species, Klebsiella species, Proteus mirabilis, Morganella morganii, and Proteus vulgaris.

The CDC points out that these drugs have a potential risk for birth defects, including anencephaly (a neural tube defect that causes a baby to be born with an underdeveloped brain and incomplete skull), heart defects, and orofacial clefts, i.e. splits or opening in the lip and roof of the mouth. That link is what makes these findings so “concerning," lead study author Elizabeth Ailes, Ph.D., tells SELF.

The American College of Obstetricians and Gynecologists (ACOG) said in a committee opinion in September 2017 that “mixed” evidence has shown that these drugs are potentially harmful to a woman’s pregnancy, especially when taken in the first trimester.

The mixed evidence ACOG is referring to includes one study published in the Archives of Pediatrics and Adolescent Medicine in 2009, which included data from over 13,000 women who had given birth to a baby with a birth defect and nearly 5,000 control women who had given birth to babies in the same geographical region without birth defects. All participants were asked about their antibiotic use from one month before pregnancy through the end of their first trimester.

Results here suggested a link between the two antibiotics and several birth defects, such as anopthamalia (the absence of one or both eyes), a condition that affects blood flow through the heart, and cleft lip with cleft palate. But the study had several limitations, including the fact that participants were simply asked about their antibiotic use after their pregnancies and the prescriptions weren’t confirmed by looking at medical records. Considering that over a third of patients couldn’t remember the specific antibiotics they took, it's hard to know just how big of an effect this really is. Also, the study was observational, so the researchers can't say for certain that taking these antibiotics actually caused the birth defects, just that there was a link.

And, although this and other studies have found the potential for risks to the baby, others have found minimal risks.

Based on the research available, it's mainly pregnant women in their first trimester that should try to avoid these medications. But it ultimately should come down to a discussion of the risks and benefits with your doctor.

“In all other trimesters, these antibiotics are considered first-line therapy for a UTI in pregnancy,” board-certified ob/gyn Shannon M. Clark, M.D., an associate professor of maternal-fetal medicine at the University of Texas Medical Branch and founder of BabiesAfter35.com, tells SELF.

In fact, even ACOG adds, “prescribing sulfonamides or nitrofurantoin in the first trimester is still considered appropriate when no other suitable alternative antibiotics are available.” That's because, as we mentioned earlier, untreated UTIs can progress into a kidney infection and lead to life-threatening complications.

“Based on the evidence available, moms should not be overly concerned,” Dr. Clark says. Because the evidence is so mixed, we don't know exactly how likely it is for either of these drugs to actually cause birth defects. Unfortunately, this is often the case with medications given during pregnancy, which is why it’s important for doctors to weigh the risks and benefits of a drug before prescribing it, she says.

Doctors, midwives, nurse practitioners, and physicians assistants don't need to stop prescribing these antibiotics to pregnant women in the first trimester altogether, ACOG says. Instead, practitioners should only prescribe these particular antibiotics when no others are available or effective. Penicillins, erythromycin, and cephalosporins may be better options. Basically, these drugs should be a last resort during the first trimester—not a first-line of defense.

If you have a UTI during pregnancy (and even when you're not pregnant), your doctor should give you a urine analysis to determine the best treatment for your infection.

In some cases, the results and your personal sensitivities to certain antibiotics like penicillin or cephalosporin may indicate that nitrofurantoin or trimethoprim-sulfamethoxazole are the best way to go.

So it’s “probable” that some of the prescriptions in the CDC report were “clinically appropriate,” Dr. Ailes says. “It is also possible that health care providers prescribed these medications to women before either the provider or the women themselves knew that they were pregnant,” she says. And, unfortunately, the antibiotics might also have been prescribed by a health care provider who wasn’t up to date with ACOG’s latest recommendations, Dr. Ailes says.

That's why, when pregnant, it's especially important to insist on the urine analysis to confirm that you actually have a UTI. If you don't, you may not need to take antibiotics at all. But, if you do, you should also always ask your doctor if the antibiotic they’re prescribing is safe to take during pregnancy, Dr. Clark says. And finally, if you’re in your first trimester, it’s OK to ask whether you need to take the antibiotic ASAP or if you can wait until you’re in the second trimester, Dr. Clark says.

But, above all, if you suspect that you have a UTI, don’t try to ignore it (not that you'd really be able to). We know that “untreated UTIs can have serious consequences for the mother and baby,” Dr. Ailes says. So work with your doctor to find a solution that benefits all of you.