Mirtazapine and Pregnancy: What You Need to Know About Safety and Risks

Thinking about taking mirtazapine while pregnant? You’re not alone. Thousands of women manage depression or anxiety during pregnancy, and mirtazapine is one of the medications doctors sometimes recommend. But the big question stays: mirtazapine and pregnancy - is it safe? The answer isn’t yes or no. It’s about weighing real risks against real benefits, and understanding what the data actually shows.

What Is Mirtazapine?

Mirtazapine is an antidepressant, classified as a noradrenergic and specific serotonergic antidepressant (NaSSA). Unlike SSRIs like sertraline or fluoxetine, it works differently in the brain. It boosts levels of norepinephrine and serotonin by blocking certain receptors, which can help lift mood, improve sleep, and increase appetite. Many people find it helpful when other antidepressants cause nausea, sexual side effects, or insomnia.

It’s prescribed for major depressive disorder, generalized anxiety, and sometimes for severe nausea during pregnancy. Brand names include Remeron and Zispin. It comes in tablet form, usually taken once daily at bedtime because it can cause drowsiness. Doses range from 15 mg to 45 mg, depending on the person and their symptoms.

Why Do Women Take Mirtazapine During Pregnancy?

Untreated depression during pregnancy carries serious risks - preterm birth, low birth weight, difficulty bonding with the baby, and even postpartum depression. For some women, the emotional toll of depression is worse than any potential medication risk. If other antidepressants haven’t worked or caused bad side effects, mirtazapine may be considered because it doesn’t typically cause GI upset or sexual dysfunction - two common reasons people stop taking SSRIs.

Some OB-GYNs and psychiatrists prefer mirtazapine in early pregnancy because it’s less likely to cause fetal heart issues compared to certain other drugs. It’s also used when weight loss or poor appetite is a concern, since it often increases appetite and can help with weight gain - which can be helpful in pregnancies where nutrition is already a challenge.

What Does the Research Say About Mirtazapine and Birth Defects?

Large studies tracking thousands of pregnancies exposed to mirtazapine show no clear increase in major birth defects. A 2020 review published in Acta Psychiatrica Scandinavica analyzed data from over 1,500 pregnancies and found no consistent pattern of congenital anomalies linked to mirtazapine use. The overall risk of major malformations stayed within the baseline rate of 2-4% seen in the general population.

One small study from 2017 looked at 107 pregnancies and found one case of a heart defect - but that’s within expected rates. No study has found a dose-dependent increase in risk. That means taking a higher dose doesn’t appear to make birth defects more likely.

That said, no drug is 100% risk-free in pregnancy. The FDA classifies mirtazapine as Category C - meaning animal studies showed some risk, but human data is limited. That doesn’t mean it’s dangerous. It just means we don’t have enough large, perfect studies to say it’s completely harmless.

What About Preterm Birth or Low Birth Weight?

Some studies suggest a slightly higher chance of preterm birth (before 37 weeks) and lower birth weight in babies exposed to mirtazapine. But here’s the catch: those same outcomes are also common in women with untreated depression. So it’s hard to tell if the medication is the cause - or if the underlying mental illness is.

A 2021 study in the Journal of Clinical Psychiatry followed 214 women who took mirtazapine during pregnancy and compared them to 312 women with depression who didn’t take medication. The group taking mirtazapine had a 12% rate of preterm birth vs. 14% in the untreated group. Birth weights were similar. The researchers concluded that the medication itself didn’t appear to be the driving factor.

In other words: the biggest risk might come from not treating depression - not from taking mirtazapine.

Neonatal Adaptation Syndrome: What Happens After Birth?

Babies exposed to antidepressants near delivery can sometimes show temporary withdrawal symptoms. This is called Neonatal Adaptation Syndrome (NAS). Signs include jitteriness, irritability, feeding difficulties, mild breathing problems, or sleep disturbances. These usually resolve within days to a couple of weeks.

With mirtazapine, reports of NAS are rare. In fact, it’s less commonly associated with this than SSRIs. That’s likely because mirtazapine doesn’t strongly affect serotonin reuptake like SSRIs do. A 2022 review in Archives of Women’s Mental Health found only 3 documented cases of possible NAS out of 200+ exposures - and all resolved without treatment.

If you’re taking mirtazapine late in pregnancy, your doctor may monitor your baby for the first 48-72 hours after birth. But most babies are fine.

Is Mirtazapine Safe While Breastfeeding?

Yes - and that’s one reason it’s often preferred over other antidepressants for nursing mothers. Mirtazapine passes into breast milk in very small amounts. Studies measuring levels in infant blood found concentrations below 1% of the mother’s dose. No adverse effects on infant weight gain, sleep, or development have been reported in over 100 exposed infants.

The American Academy of Pediatrics lists mirtazapine as compatible with breastfeeding. The LactMed database from the National Library of Medicine says it’s a reasonable choice for nursing mothers who need an antidepressant.

If your baby seems unusually sleepy, fussy, or has trouble feeding, talk to your pediatrician. But most babies show no signs at all.

When Might Mirtazapine Be a Better Choice?

Not every antidepressant works for every person. Here’s when mirtazapine might be the best option:

• You’ve tried SSRIs and had bad side effects like nausea, insomnia, or loss of libido
• You’re struggling with poor appetite or weight loss during pregnancy
• You have severe anxiety with trouble sleeping - mirtazapine helps both
• You’re planning to breastfeed and want a medication with low milk transfer
• Your depression is moderate to severe and hasn’t improved with therapy alone

It’s not the first-line choice for every pregnancy, but it’s a solid option when others fail.

What About the First Trimester?

The first trimester is when the baby’s organs are forming - so that’s when most people worry the most. But mirtazapine doesn’t appear to increase the risk of heart, brain, or limb defects during this time. The largest study to date, from the Norwegian Mother and Child Cohort, included 448 first-trimester exposures and found no elevated risk of major malformations.

That doesn’t mean you should start mirtazapine without talking to your doctor. But if you’re already on it and just found out you’re pregnant, don’t panic. Stopping suddenly can cause withdrawal symptoms or a return of depression - both of which carry their own risks.

What Should You Do If You’re Pregnant and Taking Mirtazapine?

Don’t stop cold turkey. Tapering off should only be done under medical supervision. Here’s what to do:

1. Call your OB-GYN and psychiatrist together. Coordinate care - they need to talk to each other.
2. Don’t switch medications unless necessary. Changing drugs mid-pregnancy can destabilize your mood.
3. Keep track of your symptoms. Use a mood journal if you can. Note sleep, appetite, energy, and anxiety levels.
4. Ask about therapy. Cognitive behavioral therapy (CBT) works well with medication and can reduce the dose needed.
5. Get regular prenatal care. Monitoring fetal growth is especially important if you’ve had depression or are on medication.

Many women take mirtazapine throughout pregnancy and deliver healthy babies. The goal isn’t to be medication-free - it’s to be mentally and physically well enough to care for your child.

Alternatives to Mirtazapine in Pregnancy

Other antidepressants are more studied in pregnancy. Here’s how they compare:

Sertraline is often the first choice because it’s the most studied and has the best safety profile overall. But if you can’t tolerate it, mirtazapine is a strong second option.

What If You’re Trying to Get Pregnant?

If you’re planning a pregnancy and taking mirtazapine, talk to your doctor before stopping or changing anything. Some women switch to sertraline ahead of conception because of more data. Others stay on mirtazapine if it’s working well.

Don’t assume you need to go off all meds. Many women conceive and carry healthy pregnancies while on antidepressants. The key is planning - not panic.

Final Thoughts: It’s About Balance

Mirtazapine isn’t perfect. But neither is untreated depression. The data tells us that for most women, the benefits of staying on mirtazapine during pregnancy outweigh the risks. Birth defects are rare. Withdrawal in newborns is uncommon. Breastfeeding is safe.

What matters most is your mental health. If you’re stable, sleeping well, eating enough, and able to connect with your baby - you’re doing better than you think.

Work with your care team. Don’t make changes alone. And remember: taking care of your mind is part of taking care of your baby.