Trichomoniasis in pregnancy is treated with oral metronidazole, taken as a multi-day course, and it's considered safe in any trimester. Tinidazole is avoided during pregnancy because there's less safety data. Treatment doesn't undo all obstetric risk, so screen early, treat your partner at the same time, and avoid alcohol during the medication.
with the right treatment
testing, not symptoms, decides
| Item | Value |
|---|---|
| Curable? | yes — with the right treatment |
| Tested by | NAAT / lab |
| Often | no symptoms |
| If you may have it | get tested — testing, not symptoms, decides |
Why trichomoniasis matters more when you're pregnant
Trichomoniasis is caused by Trichomonas vaginalis, a single-celled protozoan parasite that lives in the lower genital tract. It's the most common curable STI, with an estimated 2.6 million infections in the US, and it falls disproportionately on women, who make up over 80% of cases Sex Transm Dis, 2018. About 70% of infected people have no signs or symptoms at all CDC.
That silence raises the stakes in pregnancy. An untreated infection sits in the vaginal environment doing damage you can't feel, and the immune and hormonal changes of pregnancy don't clear it. Because it inflames the genital tract, trich also makes it easier to acquire or pass other STIs, including HIV, which is a real concern when there's a baby on the way.
What the infection can do to the baby
The two outcomes clinicians watch for are preterm birth (delivery before the pregnancy reaches full term) and low birth weight (a baby born smaller than expected, which carries its own short- and long-term health risks). Trichomoniasis in pregnancy increases the chance of both CDC STI Treatment Guidelines, 2021. The leading theory is that the parasite triggers inflammation in the lower genital tract that can ripple upward and disturb the membranes and the timing of labor.
A second risk is indirect but important. By irritating and inflaming the genital tissue, trich raises your susceptibility to other sexually transmitted infections, HIV among them. Picking up a second infection during pregnancy compounds the risk to both you and the baby, one more reason not to leave a positive result untreated.
When trichomoniasis screening happens in pregnancy
There's no universal recommendation to screen every pregnant person who has no symptoms, but two situations clearly call for testing. The first is any symptoms: itching, burning, soreness, painful urination, or a clear, white, yellowish or greenish discharge with a fishy smell are worth flagging to your prenatal provider. The second is HIV: routine annual screening for trichomoniasis is recommended for women living with HIV, including during pregnancy, because the infection is both more common and more consequential in that group.
Diagnosis is straightforward. A clinician collects a vaginal swab, and modern nucleic-acid amplification tests are far more sensitive than the old microscope-slide method, catching infections that a quick wet-mount would miss. If you want the full picture of how each method works and how accurate it is, see our guide to trichomoniasis testing & diagnosis. And if you're testing because of a recent exposure rather than symptoms, the timing matters, so read up on when to test after exposure so you don't test too early and get false reassurance.
If you're noticing changes and want to know what's typical before your appointment, our overview of trichomoniasis symptoms in women walks through what each sign actually feels like. Most infections produce nothing at all, so a test beats waiting.
Safe treatment during pregnancy
The drug of choice in pregnancy is metronidazole, an antibiotic in the nitroimidazole class that kills the parasite by damaging its DNA. It's the same medication used outside pregnancy and has a long track record across all trimesters. The standard course for women is metronidazole 500 mg orally twice daily for seven days. That multi-day regimen replaced the old single 2-gram dose for women in the 2021 guidelines because it works better.
In a randomized trial, about 19% of women given the single 2-gram dose were still infected at follow-up, versus about 11% of those who took the seven-day course, roughly half the failure rate Muzny et al., Sex Transm Dis. Cutting reinfection and treatment failure is worth a few extra days of pills, especially during a pregnancy you're trying to protect.
Tinidazole, the usual single-dose alternative for non-pregnant people, is not recommended in pregnancy because there's insufficient safety data to support it. Stick with metronidazole unless your obstetrician advises otherwise.
| Regimen | Who it's for | Use in pregnancy |
|---|---|---|
| Metronidazole 500 mg orally twice daily for 7 days | Women (preferred) | Considered safe; the preferred course |
| Metronidazole 2 g orally, single dose | Men / partner treatment | Discuss with clinician; the 7-day course is preferred for women |
| Tinidazole 2 g orally, single dose | Alternative for non-pregnant adults | Avoid — insufficient pregnancy safety data |
A few practical rules make or break treatment. Don't drink any alcohol while you're on metronidazole, and for a short window after, since the combination can cause a disulfiram-like reaction with nausea, flushing, and vomiting. Finish every pill even after symptoms fade, because stopping early leaves parasites behind. And ask whether your partner needs treating, since reinfection from an untreated partner is common, so both of you should be treated at the same time, and many clinicians retest sexually active women about three months after treatment. For the full breakdown of doses and how the drug works, see trichomoniasis treatment.
On breastfeeding: metronidazole does pass into breast milk, and the multi-day oral course is generally considered compatible with nursing. Some clinicians prefer the lower divided dose over a single large dose while breastfeeding, and a few suggest a short pump-and-discard window after a large single dose, so confirm the plan with your own provider, who knows your situation.
Reducing transmission around delivery
Trichomoniasis spreads through sex, including penis-to-vagina, vagina-to-penis, and vagina-to-vagina contact, not casually. The goal before delivery is to clear the infection and keep it cleared. Treating an active infection before you go into labor lowers the genital-tract inflammation tied to preterm birth and removes the small possibility of passing the parasite to the baby during a vaginal delivery.
- Treat early once a positive test comes back, rather than waiting, so the seven-day course is well behind you before your due date.
- Make sure your partner is treated at the same time, otherwise you can be reinfected right before delivery.
- Use condoms every time after treatment to keep new exposures out while you finish the pregnancy.
- Follow your provider's advice on a retest if there's any chance of reinfection before delivery.
When to see a clinician
Bring up any genital itching, burning, soreness, painful urination, or unusual discharge with your prenatal provider, and don't self-diagnose or wait it out during pregnancy. You should also ask to be tested if a partner is diagnosed with trichomoniasis or another STI, if you have HIV, or if you've had a new sexual partner. If you'd rather check discreetly between visits, you can get tested and bring the result to your obstetrician.