Pregnancy and hair-loss treatments: what do we really know about the risks for the baby?

Hair loss affects millions of people worldwide and, in many cases, requires treatment for months or even years. However, when a desire for pregnancy arises or an unexpected pregnancy occurs, one of the most frequent questions in consultation is inevitable:

Should I stop my treatment?

This concern worries not only women. Many men who take finasteride or dutasteride also ask whether their treatment could affect a future pregnancy of their partner or increase the risk of malformations in the baby.

The answer, as is often the case in medicine, is not a simple "yes" or "no." It depends on the drug, the route of administration, the stage of pregnancy and the quality of the available scientific evidence.

In recent years, numerous studies have made it possible to understand much better the safety profile of the main treatments used against hair loss. Thanks to them, we now have far more precise international recommendations that allow decisions to be made based on evidence and not on fear.

In this article we review what we really know about minoxidil, finasteride and dutasteride, what their possible effects are during pregnancy, what happens when it is the father who receives the treatment, and what the main international scientific societies currently advise.

What does it mean for a drug to be teratogenic?

A teratogenic effect is the ability of a substance to alter the normal development of the embryo or fetus, producing congenital malformations or permanent functional alterations.

Not all drugs cross the placenta in the same way. Nor do they all cause harm, even when they reach the fetus.

For a real risk to exist, several factors must coincide:

• that the drug reaches the fetal circulation;
• that the dose is sufficient;
• that the exposure occurs during a critical period of embryonic development;
• that the developing tissue is sensitive to that mechanism of action.

The period of greatest vulnerability corresponds approximately to the first weeks of pregnancy, when most organs are formed. This is why many drugs considered potentially teratogenic are contraindicated especially during the first trimester.

It is important to remember that the absence of studies in pregnant women does not necessarily mean that a drug is dangerous. In many cases there are simply no clinical trials for ethical reasons, so recommendations are based on animal studies, isolated clinical cases or data from pharmacovigilance registries.

Do all hair-loss treatments carry the same risk?

No.

This is probably the most important message of the whole article.

Each drug has a completely different mechanism of action and, therefore, a distinct safety profile during pregnancy.

In general terms, we can divide the treatments into three broad groups:

1. Drugs with a demonstrated or highly probable teratogenic risk, such as the 5-alpha-reductase inhibitors (finasteride and dutasteride), which can interfere with the normal development of the external genitalia of the male fetus.
2. Drugs with limited data and uncertain risk, such as minoxidil, for which the available information is scarce and recommendations are based mainly on the precautionary principle.
3. Non-pharmacological treatments, which in many cases can be maintained or adapted during pregnancy under medical supervision.

Understanding these differences makes it possible to avoid both unnecessary exposure to potentially dangerous drugs and the unjustified discontinuation of treatments when the real risk is very low.

Minoxidil: is it safe during pregnancy?

Minoxidil is probably the most widely used treatment in the world for androgenetic alopecia. Initially developed as an oral antihypertensive, one of its most striking side effects was observed to be hair growth, which led to the development of its topical formulation.

Today there are two main forms of administration:

• Topical minoxidil, applied directly to the scalp.
• Oral minoxidil, increasingly used at low doses (Low-Dose Oral Minoxidil, LDOM) in the treatment of different types of alopecia.

Although both contain the same active ingredient, their systemic exposure — and therefore their implications during pregnancy — are different.

Topical minoxidil

Topical minoxidil has a relatively low skin absorption.

Under normal conditions, approximately 1% to 2% of the applied dose reaches the systemic circulation, although this figure may increase if:

• there is inflammation of the scalp;
• it is applied to injured skin;
• amounts higher than recommended are used;
• very extensive applications are performed;
• it is combined with techniques that increase skin penetration, such as microneedling.

This low absorption explains why the treatment is usually very safe in the general population.

However, during pregnancy the question changes.

Are there studies in pregnant women?

There are no controlled clinical trials, for ethical reasons.

The available information comes from:

• published clinical cases;
• pharmacovigilance registries;
• experimental studies;
• systematic reviews.

The data are limited and do not allow a cause-and-effect relationship to be established with certainty.

Nevertheless, a few isolated cases of newborns exposed in utero who presented congenital anomalies or neonatal hypertrichosis have been described. Because of the small number of cases and the presence of multiple confounding factors, it cannot be affirmed that minoxidil was directly responsible, but it is also not possible to completely rule out a risk.

For this reason, the main scientific societies adopt a cautious stance.

What do the international guidelines recommend?

Current recommendations are fairly consistent.

During pregnancy:

• it is advised to stop topical minoxidil;
• if pregnancy is discovered while the patient is using it, it should be stopped and discussed with the doctor;
• accidental exposure in the first weeks does not automatically imply that a malformation will occur, so it should not cause unnecessary alarm.

The recommendation is based mainly on the precautionary principle, since the available evidence remains insufficient to guarantee its safety.

What about breastfeeding?

Minoxidil may be excreted in small amounts in breast milk.

Although the information is scarce and no serious problems have been consistently described, most guidelines recommend avoiding its use during breastfeeding or carefully assessing the benefit-risk balance in each case.

Oral minoxidil

In recent years, the use of low-dose oral minoxidil has grown enormously in dermatology and trichology.

Its efficacy has been demonstrated in both men and women for different forms of alopecia, especially when topical treatment is insufficient or poorly tolerated.

However, from the point of view of pregnancy, the situation changes significantly.

Unlike the topical formulation, oral minoxidil reaches much higher plasma concentrations and easily crosses the maternal systemic circulation.

As a result, the potential fetal exposure is significantly greater.

What do we know about the fetal risk?

The clinical evidence remains limited, but precisely because of this greater systemic exposure, the international recommendations are stricter.

Currently:

• oral minoxidil is not recommended during pregnancy;
• nor should it be started in women with an immediate desire for pregnancy;
• if a patient becomes pregnant while taking it, she should consult her doctor as soon as possible to assess stopping the treatment and to arrange appropriate follow-up.

There are no studies that conclusively demonstrate an increase in malformations, but the absence of evidence is not equivalent to proof of safety.

Should it be stopped before trying to conceive?

Yes.

Although there is no universally established interval, most specialists advise stopping the treatment before attempting conception, in order to avoid any exposure during the first weeks of embryonic development, which constitute the period of greatest susceptibility.

In clinical practice, the cosmetic benefit of continuing the treatment during that period does not outweigh the existing uncertainty about its fetal safety.

Key messages about minoxidil

• Topical minoxidil has low but not zero systemic absorption.
• The data available in pregnant women are scarce and do not allow its safety to be guaranteed.
• The main international guidelines recommend stopping minoxidil during pregnancy as a precaution.
• Oral minoxidil produces a much greater systemic exposure and should not be used during gestation.
• Accidental exposure at the start of pregnancy does not automatically mean a high risk of malformations, but it should be assessed by a healthcare professional.

Finasteride: the treatment with the strongest evidence of risk during pregnancy

If there is a hair-loss drug whose relationship with teratogenicity is clearly established, it is finasteride.

Unlike minoxidil, whose use during pregnancy is discouraged mainly for lack of sufficient data, finasteride has a biological mechanism that perfectly explains why it can be harmful to fetal development, especially in male fetuses.

For this reason, all regulatory agencies and international scientific societies agree on a clear recommendation: finasteride is contraindicated during pregnancy.

How does finasteride work?

Finasteride inhibits the enzyme 5-alpha-reductase type II, responsible for converting testosterone into dihydrotestosterone (DHT).

DHT plays an essential role in:

• the development of the prostate;
• the growth of the hair follicle;
• androgenetic alopecia;
• the development of the external genitalia of the male fetus.

It is precisely this last aspect that explains the concern during gestation.

During the first weeks of pregnancy, DHT is essential for the correct formation of the penis, the scrotum and other male genital structures.

If its production is blocked at a critical moment of embryonic development, congenital alterations known as virilisation disorders may appear.

What do the experimental studies show?

Most of the evidence comes initially from animal studies.

When pregnant females were exposed to finasteride during the period of organogenesis, the following were observed:

• alterations in the development of the male external genitalia;
• hypospadias;
• ambiguous genitalia;
• reduced prostate size;
• alterations of the urogenital tract.

These findings were consistent and dependent on the administered dose.

Although animal studies cannot always be directly extrapolated to humans, the physiological mechanism involved is sufficiently well known to justify the current recommendations.

What do we know in humans?

For ethical reasons, clinical trials have never been conducted in pregnant women.

The available information comes from:

• accidental exposures;
• pharmacovigilance registries;
• case series;
• systematic reviews.

Fortunately, the number of documented exposures is small, so there is not a large amount of clinical cases.

However, given the experimental evidence and the drug's mechanism of action, it would not be ethical to attempt to demonstrate its safety through prospective studies.

In medicine, there are situations in which biological knowledge is solid enough to establish a contraindication without needing randomised clinical trials.

Finasteride is one of those examples.

Is there a risk with topical finasteride?

In recent years, topical formulations of finasteride have appeared in an attempt to reduce systemic exposure.

Various studies have shown that systemic absorption is much lower than with the oral route.

Nevertheless, it is not zero.

There are currently no sufficient studies demonstrating its safety during pregnancy.

Therefore, the main guidelines consider that topical finasteride should also be avoided during gestation.

The lower absorption does not guarantee the absence of fetal risk.

Can a woman handle finasteride tablets?

This is another very frequent question.

Finasteride tablets are coated with a protective film that prevents direct contact with the active ingredient while they remain intact.

Therefore:

• a whole tablet does not pose a relevant risk through simple contact;
• on the other hand, broken, crushed or damaged tablets can release the drug.

Pregnant women or those who may become pregnant should not handle broken or crushed tablets, since there is a theoretical risk of skin absorption.

Although the amount absorbed would probably be very small, the international recommendation is to avoid this exposure completely.

Should contraception be used?

In women of childbearing age who receive finasteride for exceptional indications (for example, certain forms of female alopecia), it is essential to carefully assess the risk of pregnancy.

In clinical practice, most specialists recommend:

• confirming the absence of pregnancy before starting treatment;
• using an effective contraceptive method for the duration of the treatment;
• stopping the drug if a pregnancy is planned.

The decision must always be individualised for each patient.

Dutasteride: is it different?

Dutasteride belongs to the same pharmacological family as finasteride, but it has some important differences.

Whereas finasteride mainly inhibits 5-alpha-reductase type II, dutasteride blocks both type I and type II, producing a much more intense suppression of DHT.

This explains its high clinical efficacy, but it also justifies why the recommendations during pregnancy are even stricter.

The importance of its long half-life

One of the main differences between the two drugs is their persistence in the body.

Finasteride disappears relatively quickly after stopping treatment.

Dutasteride, on the other hand, has a half-life of approximately five weeks and may take several months to be completely eliminated.

From a practical point of view, this means that:

• it should not be started in women with an upcoming desire for pregnancy;
• if a pregnancy is planned, the treatment must be stopped well in advance;
• planning is especially important because of the drug's persistence in the body.

Current recommendations

The main scientific societies agree that:

• Oral finasteride: contraindicated during pregnancy.
• Topical finasteride: should also be avoided due to insufficient data.
• Dutasteride: contraindicated during pregnancy and in women who may become pregnant if there is no effective contraception.

In all cases, the decision must be based on an individual assessment of the expected benefit against the potential risk.

Key messages about finasteride and dutasteride

• The teratogenic risk of 5-alpha-reductase inhibitors is supported by a solid biological mechanism and by experimental studies.
• The main concern relates to the development of the external genitalia of the male fetus during the first weeks of gestation.
• Both oral finasteride and dutasteride are contraindicated during pregnancy.
• Topical finasteride reduces systemic exposure, but it cannot currently be considered safe during gestation either.
• Dutasteride, because of its long half-life, requires special planning before a pregnancy project.

What happens if it is the man who takes finasteride or dutasteride?

This is probably the question that most worries couples who wish to have a child.

"I have been taking finasteride for years. Can it affect my partner's pregnancy?"

"Is there a risk of malformations if the father is on treatment?"

The answer is reassuring.

With the scientific evidence available to date, it has not been demonstrated that treatment of the father with finasteride or dutasteride increases the risk of congenital malformations in the baby.

However, it is worth understanding why.

Does finasteride pass into semen?

Yes, but in extremely small amounts.

Various studies have shown that small amounts of finasteride can be detected in the seminal fluid of treated men.

Nevertheless, the concentration is so low that the amount to which the partner could be exposed during sexual intercourse is far below that needed to produce a biological effect on fetal development.

Pharmacokinetic models estimate that this exposure is thousands of times lower than the dose capable of altering embryonic development.

For this reason, indirect exposure through semen is considered clinically irrelevant.

Are there cases of malformations related to the father's treatment?

To date, there is no solid scientific evidence demonstrating an increase in the risk of congenital anomalies when the father receives finasteride or dutasteride at the time of conception.

The available observational studies and pharmacovigilance registries have not identified a consistent increase in:

• congenital malformations;
• spontaneous miscarriages;
• obstetric complications;
• disorders of child development.

Although no study can affirm that the risk is absolutely zero, the accumulated evidence is clearly reassuring.

So why is there so much concern?

Largely because the risk of a direct exposure of the mother during pregnancy is often confused with the situation in which only the father is treated.

These are two completely different scenarios.

In the pregnant woman, the drug can reach the fetal circulation directly.

By contrast, when it is the man who receives the treatment, the potential exposure of the embryo through semen is minimal and, according to current knowledge, insufficient to produce a teratogenic effect.

Can it affect male fertility?

Here the answer is different.

Although the teratogenic risk does not seem to increase, some studies have observed that 5-alpha-reductase inhibitors can modify certain semen parameters.

In some patients the following have been described:

• a decrease in ejaculate volume;
• a reduction in the number of spermatozoa;
• a drop in motility;
• slight alterations of sperm morphology.

Most of these changes are modest, variable between individuals and, in many cases, reversible after stopping treatment.

It is important to stress that the majority of treated men maintain normal fertility.

Do all men show these changes?

No.

The response is highly variable.

Many patients never experience any significant alteration.

Others may present discreet modifications with no clinical repercussion.

However, in men whose fertility is already compromised or who have other associated factors (age, varicocele, smoking, obesity or hormonal disorders), these drugs could contribute to reducing semen quality even further.

For this reason, some specialists recommend individually assessing the temporary discontinuation of the treatment when there are difficulties in achieving a pregnancy.

Should finasteride be stopped if the couple is trying to conceive?

In general terms, there is no universal recommendation to stop the treatment solely because of a possible risk to the baby, since this risk has not been demonstrated.

Nevertheless, if the couple has fertility problems or has been trying for several months to conceive without success, it may be reasonable to review all potentially involved factors, including the drug treatment.

The decision must be individualised after assessing:

• the severity of the alopecia;
• the psychological impact of stopping the treatment;
• the age of the couple;
• the results of the fertility work-up.

And what about dutasteride?

The conclusions are very similar.

Although dutasteride can also be detected in semen at very low concentrations, there is no evidence that paternal treatment increases the risk of fetal malformations.

Nevertheless, because its suppression of DHT is more intense and its half-life much longer, some specialists consider it prudent to assess stopping it in certain cases of male infertility, especially when there are documented semen alterations.

This recommendation is based mainly on the possible effect on fertility and not on a teratogenic risk for the future baby.

What do the scientific societies advise?

Current recommendations are clear:

• Treatment of the father with finasteride or dutasteride is not an indication to avoid pregnancy.
• It is not recommended to systematically stop these drugs solely out of fear of fetal malformations.
• If there are male fertility problems, a complete andrological assessment should be carried out before attributing the cause to the treatment.

Key messages about paternal treatment

• The available scientific evidence does not demonstrate an increase in the risk of malformations when the father takes finasteride or dutasteride.
• The amounts present in semen are extremely low and are considered insufficient to produce teratogenic effects.
• These drugs can, however, modify some semen parameters in certain men, although the effect is usually mild and reversible.
• In couples with difficulties conceiving, the decision to maintain or stop the treatment must be individualised after a medical assessment.
• It is important to clearly distinguish two concepts: the risk to fetal development and the possible impact on male fertility.

Comparative table of the main hair-loss treatments during pregnancy

Treatment	Risk during pregnancy	Level of evidence	Male fertility	Recommendation
Topical minoxidil	Risk not demonstrated, but cannot be excluded	Moderate	No evidence of impairment	Suspend during pregnancy as a precaution
Oral minoxidil	Not recommended due to greater systemic exposure	Moderate	No evidence of impairment	Contraindicated during gestation
Oral finasteride	Contraindicated due to potential risk to the genital development of the male fetus	High	May reversibly decrease some semen parameters	Contraindicated during pregnancy
Topical finasteride	Lower systemic absorption, but not zero	Moderate	No evidence of significant impairment	Avoid during gestation
Dutasteride	Contraindicated due to its potent DHT inhibition and its long half-life	High	May alter some semen parameters; recovery may be slower after discontinuation	Contraindicated during pregnancy. In women wishing to conceive, it must be stopped several months in advance because of its prolonged persistence in the body.

Myths and facts

"If my husband takes finasteride, our baby may be born with malformations."

False. To date, the available studies have not demonstrated an increase in the risk of congenital malformations when the treatment is received solely by the father.

"Topical minoxidil does not enter the bloodstream."

False. Its systemic absorption is low, but it exists. This is why it is recommended to stop it during pregnancy as a precaution.

"All hair-loss treatments are equally dangerous."

False. Each drug has a different mechanism of action and a distinct safety profile. It is not correct to extrapolate the risk of one drug to the others.

"If I used minoxidil without knowing I was pregnant, my baby will have a malformation."

False. Accidental exposure does not automatically imply a high risk. It is advisable to stop the treatment and consult the professional following the pregnancy.

"Finasteride causes permanent infertility."

False. In some men it can modify certain semen parameters, but most of the described changes are mild and reversible after stopping treatment.

The Clínica Valorian perspective

At Clínica Valorian we believe that the best medical decision is always the one that combines scientific evidence with the individual circumstances of each patient.

Hair-loss treatments are often maintained for years and are part of the quality of life of many people. However, a pregnancy project requires carefully reconsidering their benefit-risk balance.

Our approach consists of informing clearly, avoiding unnecessary alarmism and planning any therapeutic change in advance. Most situations can be resolved safely through a personalised assessment, making it possible to protect both the patient's health and the correct development of the future pregnancy.

Evidence-based medicine does not consist only of knowing the risks, but also of correctly interpreting their real magnitude and conveying that information in an understandable way so that each patient can make decisions with confidence.

Conclusion

Current scientific evidence allows a clear message to be conveyed: the main teratogenic risk in the treatment of hair loss corresponds to maternal exposure to finasteride and dutasteride during pregnancy, while treatment received by the father has not been associated with a demonstrated increase in congenital malformations. As for minoxidil, the absence of robust data requires a cautious attitude and a recommendation to stop it during gestation.

With correct planning and individualised medical follow-up, it is possible to treat hair loss effectively without compromising the safety of a future pregnancy, reconciling the patient's well-being with the protection of fetal development.