Chlamydia in Pregnancy: Risks, Safe Treatment & What to Expect
Important: Doxycycline is contraindicated throughout pregnancy. It must not be used to treat chlamydia in pregnant women. Safe antibiotic alternatives are available — this guide covers them in full. If you are pregnant and have tested positive for chlamydia, contact your midwife, GP, or sexual health clinic without delay.
2–3%
Estimated prevalence of chlamydia in pregnant women attending UK antenatal clinics
30–50%
Of babies born to untreated mothers who develop neonatal conjunctivitis
5–6 wks
Post-treatment window before test of cure is performed in pregnancy
Why Chlamydia in Pregnancy Requires Prompt Action
Chlamydia during pregnancy creates a distinct clinical situation. The mother’s health, the developing baby, and the choice of antibiotic are all affected by pregnancy in ways that do not apply to standard chlamydia management. The first-line treatment in the non-pregnant population — doxycycline — is absolutely contraindicated in pregnancy. Alternative regimens are available, but all require careful prescribing and obstetric involvement.
The urgency of treatment in pregnancy is heightened by the risk of vertical transmission — passing the infection to the baby during birth. Approximately 50–70% of babies born vaginally to mothers with active, untreated chlamydia will acquire the infection at delivery. The consequences for the neonate range from treatable conjunctivitis to more serious neonatal pneumonia. None of these outcomes occur if the mother is diagnosed and treated before delivery.
Risks to the Mother
Chlamydia in pregnancy has been associated with several obstetric complications, though the strength of evidence varies:
- Preterm premature rupture of membranes (PPROM) — ascending chlamydial infection may contribute to weakening of the amniotic membranes, increasing risk of early rupture.
- Preterm birth — the association between untreated chlamydia and preterm delivery has been documented in several observational studies, though confounding factors make causal attribution complex.
- Postpartum endometritis — infection of the uterine lining after delivery, which can occur if chlamydia was not treated during pregnancy and ascends during or after birth.
- Low birth weight — some studies have identified an association, though this is not consistently confirmed across all populations.
The most important maternal risk is the progression to PID if chlamydia is left untreated — which carries its own risks of preterm labour and sepsis in the pregnant woman. Prompt diagnosis and treatment substantially mitigates all of these risks.
Risks to the Baby
The neonatal risks of untreated maternal chlamydia are the primary clinical driver for testing and treatment in pregnancy. Vertical transmission occurs during passage through the birth canal at the time of vaginal delivery.
Neonatal conjunctivitis (ophthalmia neonatorum)
The most common neonatal complication. Occurs in 30–50% of babies born to untreated mothers. Presents at 5–14 days of life with sticky, purulent eye discharge. Requires systemic antibiotic treatment; if untreated, can cause corneal scarring and visual impairment.
Neonatal chlamydial pneumonia
A more serious complication, developing at 1–3 months of age. Characterised by a distinctive staccato (stuttering) cough, fast breathing (tachypnoea), and patchy infiltrates on chest X-ray. Requires systemic erythromycin treatment for 14 days. Hospitalisation may be needed.
Caesarean section does not reliably prevent transmission. While transmission primarily occurs during vaginal delivery, chlamydia can ascend and infect the amniotic fluid, and neonatal exposure during caesarean section — particularly when membranes have ruptured — is possible. Treatment of the mother before delivery is the safest approach regardless of delivery mode.
Testing in Pregnancy
Chlamydia testing is not universally offered as part of the standard UK antenatal booking screen, but it is offered in many areas — particularly in regions with higher prevalence. Women who present to antenatal care should be offered testing if they have not been tested recently, have a new partner, or are under 25.
Testing method in pregnancy is the same as in the general population: a NAAT test on a self-taken low vaginal swab or a first-void urine sample. Both are safe to collect in pregnancy. Cervical sampling during a speculum examination may be performed in clinic if clinically indicated.
Tell your midwife or obstetrician. If you have tested positive for chlamydia during pregnancy — whether through a home kit, GP, or sexual health clinic — inform your antenatal team promptly. They will ensure the correct antibiotic is prescribed, arrange a test of cure, and ensure your baby is assessed after delivery.
Safe Treatment Options in Pregnancy
Treatment of chlamydia in pregnancy requires careful antibiotic selection. Doxycycline is absolutely contraindicated. Azithromycin, erythromycin, and amoxicillin are the available alternatives, each with different efficacy data, tolerability, and prescribing considerations.
| Antibiotic | Regimen | Evidence & notes |
|---|---|---|
| Azithromycin 1 g stat | Single oral dose of 1 g | Most evidence supports good efficacy and convenience. Preferred by BASHH as first option in pregnancy when specialist agrees. Test of cure at 5–6 weeks required. Some prescribers prefer erythromycin due to longer pregnancy safety data. |
| Erythromycin | 500 mg four times daily for 14 days or 250 mg four times daily for 14 days |
Longest pregnancy safety record of available options. Lower tolerability due to GI side effects at full doses — reduced dose regimen may improve compliance. Test of cure at 5–6 weeks required. |
| Amoxicillin | 500 mg three times daily for 7 days | Lower efficacy than azithromycin or erythromycin for chlamydia (approximately 90% vs 95%+). Reserved for cases where macrolides are contraindicated or not tolerated. Test of cure at 5–6 weeks required. |
| Doxycycline | — | Absolutely contraindicated in pregnancy. Causes foetal bone and teeth abnormalities. Do not prescribe or take. |
Decision with your clinical team. The choice of antibiotic in pregnancy should always be made in discussion with your midwife, GP, or obstetric team — not self-prescribed. Individual factors including gestational age, allergies, comorbidities, and local guidance influence the most appropriate choice. Access Doctor does not prescribe for chlamydia in pregnancy via online consultation alone; pregnant patients are directed to antenatal or obstetric services.
Test of Cure in Pregnancy
Unlike standard chlamydia treatment in non-pregnant adults — where a routine test of cure is not recommended — a test of cure is mandatory after chlamydia treatment in pregnancy. This is because the consequences of treatment failure are more serious (ongoing risk of neonatal infection) and because the evidence base for antibiotic efficacy in pregnancy is less robust.
The test of cure should be performed 5–6 weeks after completing antibiotic treatment, using the same NAAT methodology as the diagnostic test. A positive test of cure indicates either treatment failure or reinfection (from an untreated partner), and requires a further course of antibiotic treatment — ideally of a different agent — under specialist guidance.
Partner Notification in Pregnancy
Partner notification is as important in pregnancy as in any other clinical context — indeed, more so. Reinfection from an untreated partner during pregnancy would undermine treatment, lead to a positive test of cure, and again place the baby at risk. All recent sexual partners (past 6 months) must be informed, tested, and treated before sexual contact resumes.
A pregnant woman’s current partner should be treated promptly. If the partner is male and not pregnant, the standard regimen (doxycycline or azithromycin) applies to them. Abstain from sexual contact until both partners have completed treatment and observed the 7-day post-treatment abstinence period.
Concerned About Chlamydia in Pregnancy?
If you are not pregnant and have tested positive for chlamydia, Access Doctor (GPhC #9011198) can provide a same-day online consultation and prescription for doxycycline or azithromycin. For chlamydia in pregnancy, please contact your midwife or GP directly — prescribing in pregnancy requires obstetric-level oversight that falls outside the scope of an online pharmacy consultation.
Non-Pregnancy Consultation →Frequently Asked Questions
Can chlamydia cause a miscarriage?
There is limited and inconsistent evidence directly linking chlamydia to miscarriage. The association is stronger with preterm birth and preterm premature rupture of membranes than with first-trimester loss. However, ascending infection causing PID in early pregnancy is associated with increased miscarriage risk. The safest course is prompt diagnosis and treatment at any stage of pregnancy.
Is azithromycin safe in pregnancy?
Azithromycin is not classified as a Category A (absolutely safe) drug in pregnancy, as there are no large randomised controlled trials in pregnant women. However, a substantial body of observational data — including systematic reviews — has not found evidence of teratogenicity or significant foetal harm from azithromycin at standard doses used for chlamydia treatment. BASHH includes azithromycin as a recommended option for chlamydia in pregnancy, used under clinical supervision.
Will chlamydia affect my baby if I am treated before delivery?
If chlamydia is diagnosed and fully treated before delivery, and a test of cure confirms clearance, the risk of neonatal infection from vertical transmission is substantially reduced. Neonatal conjunctivitis and pneumonia occur as a consequence of active, untreated maternal infection at the time of delivery — not past infection that has been successfully treated.
What happens to my baby if I had untreated chlamydia during birth?
If active chlamydia was present at delivery and your baby was not exposed prophylactically, your neonatal team should be informed. Babies exposed to chlamydia at birth are monitored for conjunctivitis (typically appearing at 5–14 days) and pneumonia (appearing at 1–3 months). If neonatal conjunctivitis develops, systemic erythromycin for 14 days is the treatment of choice — topical antibiotics alone are insufficient as they do not prevent pneumonia.
Should I tell my midwife I have chlamydia?
Yes, absolutely. Your midwife and obstetric team need to know about any infection diagnosed during pregnancy. This is not a matter of stigma — chlamydia is extremely common and your clinical team’s only concern is your health and your baby’s. Informing your midwife ensures you receive the correct antibiotic, a test of cure is arranged, and the neonatal team can assess your baby appropriately after delivery.
Can I take chlamydia treatment while breastfeeding?
If you are diagnosed with chlamydia post-delivery while breastfeeding, the antibiotic choice depends on individual circumstances. Azithromycin is excreted into breast milk but at low concentrations, and short-term use is generally considered acceptable under clinical guidance. Erythromycin is also an option. Doxycycline was previously cautioned against in breastfeeding but current evidence and many guidelines suggest short-term use (up to 3 weeks) is of low risk — discuss with your prescriber or a pharmacist who can review your specific situation.
References
- BASHH. UK National Guideline for the Management of Infection with Chlamydia trachomatis. 2025. Available at: www.bashh.org/guidelines
- NICE. Chlamydia — uncomplicated genital: Clinical Knowledge Summary. 2025. Available at: cks.nice.org.uk
- Rahangdale L, Guerry S, Bauer HM, et al. An observational cohort study of Chlamydia trachomatis treatment in pregnancy. Sex Transm Dis. 2006;33(2):106–110.
- Rours GI, Hammerschlag MR, Ott A, et al. Chlamydia trachomatis as a cause of neonatal conjunctivitis in Dutch infants. Pediatrics. 2008;121(2):e321–e326.
- NHS. Chlamydia: Treatment. 2023. Available at: www.nhs.uk/conditions/chlamydia/treatment/
- BNF. Prescribing in Pregnancy. British National Formulary. 2025. Available at: bnf.nice.org.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Chlamydia in pregnancy is a clinical situation requiring management by a qualified healthcare professional — ideally your midwife, GP, or obstetric team. Doxycycline is contraindicated in pregnancy and must not be taken. If you are pregnant and have tested positive for chlamydia, contact your antenatal team immediately. In a medical emergency, call 999.