BV, Thrush and UTIs in Pregnancy: What Is Treated and Safe

If you are pregnant and think you have BV, thrush or a urinary infection, speak to your midwife or GP first: all three have a treatment in pregnancy, and the choice changes. The NHS says some thrush medicines should not be used while you're pregnant, NICE says a UTI in pregnancy gets an antibiotic immediately, and BV gets one when it causes symptoms. Live cultures showed no safety problems and no benefit in four trials.^{1, 2, 3, 4} Part of the Wellgard guide to what BV is and why it starts.

Sources checked on 29 October 2026.

Why does pregnancy change the picture?

The NHS lists pregnancy among the triggers for thrush and the things that help bacteria reach the bladder.^{5, 6} Discharge also increases: NICE says it "is common during pregnancy", but itching, soreness, an unpleasant smell or pain on passing urine may mean an infection, with a swab "if there is doubt about the cause".³ So a midwife or GP decides.

Is BV common in pregnancy, and does it matter?

Common and usually harmless. The NHS says there is "a small chance of complications, such as premature birth or miscarriage", and that BV "causes no problems in the majority of pregnancies".⁷ Across 32 studies and 30,518 pregnant women, BV without symptoms more than doubled the odds of preterm delivery (odds ratio 2.16) and raised the odds of late miscarriage (odds ratio 6.32).⁸ Antibiotics do not remove that risk in trials: in 21 trials of 7,847 women they eradicated BV (risk ratio 0.42) and reduced late miscarriage (two trials) but did not reduce preterm birth before 37 weeks (risk ratio 0.88; 13 trials, 6,491 women).⁹ Hence symptoms first: NICE says "Consider oral or vaginal antibiotics" for BV in pregnant women; its clinical summary says "Routine screening for BV should not be offered to pregnant women".^{3, 11} See what untreated BV leads to.

Is metronidazole safe in pregnancy?

For symptomatic pregnant women "Oral metronidazole is the treatment of choice", with metronidazole gel or clindamycin cream as alternatives, and "Intravaginal clindamycin cream is not recommended in the first trimester".¹¹ On birth defects the pooled studies agree: odds ratios of 0.93 (1995, seven studies), 0.96 and 1.08 (two analyses in a 2020 US review) and 1.15 (0.98 to 1.34, not significant; 2021, 24 studies).^{10, 12, 13} The 2021 review also pooled five observational studies and found higher odds of miscarriage (odds ratio 1.72), but its authors asked for randomised trials "to assess the role of the underlying infection".¹³ The tablet's licence calls the pregnancy evidence inadequate, notes many years of use with no apparent ill consequence, and rules out short high-dose courses in pregnancy.²³ Your GP or midwife weighs this and sets the dose and course. Outside pregnancy: how BV is treated in the UK.

How is thrush treated in pregnancy?

With a cream or pessary first, after advice. The NHS says "If you get thrush when you're pregnant, it can easily be treated", and to talk to your doctor, pharmacist or midwife because "there are some thrush medicines you should not use while you're pregnant".¹ NICE says "Offer vaginal imidazole (such as clotrimazole or econazole)", a cream or pessary; the NHS fluconazole page says the oral tablet "is not usually recommended in pregnancy but may be used if the benefits outweigh the risks".^{3, 14} In a Danish cohort of 1.4 million pregnancies, oral fluconazole at 7 to 22 weeks was associated with more spontaneous abortions (hazard ratio 1.48, 1.23 to 1.77).¹⁵ The Cochrane review of ten trials opens with "There is no evidence that thrush in pregnancy is harmful to the baby".¹⁶ See vaginal thrush.

Are UTIs in pregnancy always treated, and why?

Yes. NICE says "Offer an immediate antibiotic prescription" to pregnant women with a lower UTI, after a urine sample has gone for culture; bacteria found without symptoms get an antibiotic too, because in pregnancy they are "a risk factor for pyelonephritis and premature delivery".² The GP chooses an antibiotic NICE lists as suitable in pregnancy, guided by the culture result. In the Cochrane review, antibiotics for symptomless bacteria may reduce kidney infection (risk ratio 0.24, low-certainty evidence).¹⁷ UTIs are "usually caused by bacteria from poo entering the urinary tract", pregnancy heads the NHS risk list, and the NHS says ask your doctor before cranberry or D-mannose in pregnancy.⁶ Outside pregnancy: cystitis and the red flags and recurrent UTIs.

Can live cultures be taken in pregnancy, and do they help?

Four trials found no safety problems and no benefit. In four UK maternity units, 304 women took two lactobacillus strains or placebo daily to delivery: BV at 18 to 20 weeks was 15% against 9%, not significant, and the capsules "did not modify the vaginal microbiota".⁴ In Canada, 86 women took the same pair for 12 weeks: 30% of both groups normalised, with "no adverse issues".¹⁸ In two Israeli trials of a six-species capsule (100 and 47 women), infections were 29% against 27% and 67% against 48%, neither significant.^{19, 20} A 2026 pooled analysis of 18 studies and 3,705 women found no significant effect on BV (odds ratio 0.91) or thrush (odds ratio 0.65).²¹ "Safe" is not a benefit: ask your midwife or GP before any supplement. More: taking live cultures while pregnant or breastfeeding.

What should never be used in pregnancy?

Boric acid pessaries: guidelines "recommend IBA avoidance in pregnancy" and "safety data are sparse" (boric acid in pregnancy).²² Oral antifungal tablets, unless a prescriber has judged that the benefit outweighs the risk.¹⁴ Douches, deodorants and perfumed soaps or bath products.^{1, 5} Any cream or pessary nobody has advised; antifungal creams also damage condoms and diaphragms.⁵ For a urinary infection, nothing you drink is a treatment.⁶

Can a miscarriage cause a UTI, and can a UTI affect the pregnancy?

No study has tested whether a miscarriage causes a UTI and no NHS page links them; bleeding in pregnancy means contacting your midwife or doctor immediately.¹ A UTI can affect the pregnancy if it climbs: the NHS warns that some UTI symptoms "could be symptoms of a kidney infection", which "can be serious if it's not treated as it could cause sepsis".⁶

When do I call the midwife, the maternity unit or 999?

Call your midwife if your discharge "smells unpleasant or strange", is green or yellow, or comes with itch, soreness or pain when you pee; contact your midwife or doctor immediately if "you have any vaginal bleeding while you're pregnant".¹ For urinary symptoms, pregnancy alone means an urgent GP appointment or NHS 111; so do a very high or low temperature, shivering, pain in the lower tummy or back under the ribs, blood in your pee, or symptoms that worsen or have not improved within 48 hours.⁶ Call 999 or go to A&E if you are confused, drowsy or have difficulty speaking.⁶

What we don't know

Whether antibiotics for BV found by screening, rather than by symptoms, protect the baby: the trials above cleared BV without reducing preterm birth, and screening itself has never been tested.^{9, 10} Whether the higher miscarriage odds seen with metronidazole belong to the medicine or to the infection it treats: observational studies cannot separate the two, and the same review flagged one defect, hydrocephaly, in two studies as needing confirmation.¹³ Whether any live-culture strain, dose or timing helps in pregnancy: four placebo-controlled trials and the 2026 pooled analysis found none.^{4, 21}

Frequently asked questions

Can you use thrush cream when pregnant?

After advice, yes: talk to your doctor, pharmacist or midwife first; NICE's pregnancy treatment is a vaginal imidazole such as clotrimazole, as a cream or pessary.^{1, 3}

Can I take live cultures while pregnant?

Four placebo-controlled trials, including a UK trial of 304 women, found no reduction in BV or thrush and no safety problems.^{4, 21} Ask your midwife or GP first.

Will a UTI harm my baby?

One dealt with promptly is unlikely to. The risk NICE names is kidney infection and premature delivery, which is why every UTI in pregnancy gets an antibiotic at once.²

Sources

1. NHS. Vaginal discharge in pregnancy. Reviewed 17 April 2024. nhs.uk.
2. NICE NG109. Urinary tract infection (lower), 1.1.5 to 1.2.2. 31 October 2018. nice.org.uk.
3. NICE NG201. Antenatal care, 1.4.10 to 1.4.14. 19 August 2021. nice.org.uk.
4. Husain S, et al. Oral probiotics in pregnancy: placebo-controlled trial, 304 women, four UK maternity units. BJOG, 2020. PubMed 30932317.
5. NHS. Thrush in men and women. Reviewed 28 July 2023. nhs.uk.
6. NHS. Urinary tract infections (UTIs). Reviewed 11 July 2025. nhs.uk.
7. NHS. Bacterial vaginosis. Reviewed 19 June 2026. nhs.uk.
8. Leitich H, Kiss H. Asymptomatic BV and pregnancy outcome: meta-analysis, 32 studies, 30,518 women. Best Practice & Research Clinical Obstetrics & Gynaecology, 2007. PubMed 17241817.
9. Brocklehurst P, et al. Antibiotics for BV in pregnancy: Cochrane review, 21 trials, 7,847 women. Cochrane Database of Systematic Reviews, 2013. PubMed 23440777.
10. Kahwati LC, et al. BV screening in pregnancy: US task force evidence review, 44 studies. JAMA, 2020. PubMed 32259235.
11. NICE Clinical Knowledge Summaries. Bacterial vaginosis: management. Last revised July 2023. cks.nice.org.uk.
12. Burtin P, et al. Safety of metronidazole in pregnancy: meta-analysis, seven studies. American Journal of Obstetrics and Gynecology, 1995. PubMed 7856680.
13. Ajiji P, et al. Metronidazole in pregnancy: systematic review and meta-analysis, 24 studies. European Journal of Obstetrics & Gynecology and Reproductive Biology: X, 2021. PubMed 34136799.
14. NHS. Pregnancy, breastfeeding and fertility while taking fluconazole. Reviewed 22 October 2026. nhs.uk.
15. Mølgaard-Nielsen D, et al. Oral fluconazole in pregnancy and miscarriage: Danish cohort, 1.4 million pregnancies. JAMA, 2016. PubMed 26746458.
16. Young GL, Jewell D. Topical treatment for thrush in pregnancy: Cochrane review, ten trials. Cochrane Database of Systematic Reviews, 2001. PubMed 11687074.
17. Smaill FM, Vazquez JC. Antibiotics for asymptomatic bacteriuria in pregnancy: Cochrane review, 15 trials, over 2,000 women. Cochrane Database of Systematic Reviews, 2019. PubMed 31765489.
18. Yang S, et al. Two-strain oral lactobacilli in pregnancy: placebo-controlled trial, 86 women, Canada. Nutrients, 2020. PubMed 32019222.
19. Yefet E, et al. Oral probiotic and vulvovaginal infection in pregnancy: placebo-controlled trial, 100 women, Israel. Nutrients, 2024. PubMed 39771026.
20. Nachum Z, et al. Oral probiotics and recurrent vulvovaginal infection in pregnancy: placebo-controlled trial, 47 women, Israel. Nutrients, 2025. PubMed 39940318.
21. Liu Z, et al. Probiotics in pregnancy: meta-analysis, 18 studies, 3,705 women. Acta Obstetricia et Gynecologica Scandinavica, 2026. PubMed 42047468.
22. Mittelstaedt R, et al. Safety of intravaginal boric acid in pregnancy: narrative review. Sexually Transmitted Diseases, 2021. PubMed 34561373.
23. Metronidazole 400 mg tablets: Summary of Product Characteristics, section 4.6. Revised 4 May 2023. medicines.org.uk.

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