Had vaginal or anal sex without a condom in the last 72 hours with someone who has HIV or whose status you don’t know? Go to an emergency department or sexual health clinic now and ask about PEP (post-exposure prophylaxis). Tell them you’re pregnant or recently gave birth. PEP must start within 72 hours, ideally within 24.

A possible exposure while you’re pregnant, or soon after birth, can feel frightening because you’re thinking about your baby as well as yourself. The good news is that there are clear steps that protect you both.

Why the risk is higher

A 2018 study found that the chance of getting HIV through vaginal sex was higher during pregnancy, and higher still in the six months after giving birth. The calculator multiplies the per-act risk of receptive vaginal sex by 2.82 during pregnancy (the study’s estimate from week 14 on) and by 3.97 after birth.

For one act of vaginal sex with a man who has HIV and isn’t on treatment, that means:

  • Not pregnant: 0.08% (about 1 in 1,200)
  • Pregnant: 0.23% (about 1 in 440)
  • After giving birth: 0.32% (about 1 in 310)

With a partner of unknown status the risk is usually much lower, but the same increase applies.

PEP during pregnancy and breastfeeding

CDC guidelines say pregnancy and breastfeeding are not reasons to withhold PEP. If you’ve had an exposure that calls for PEP, you should be offered it. Your clinician may consult an HIV specialist, because pregnancy can lower the levels of some HIV medicines and doses may need adjusting.

PEP works the same way as for anyone else: start within 72 hours, take it every day for 28 days, and have follow-up HIV tests 4 to 6 weeks and 12 weeks after the exposure. See how to get PEP.

Protecting your baby

HIV can pass to a baby during pregnancy, childbirth and breastfeeding. That’s why finding out early matters so much. If you did get HIV, starting treatment quickly protects your baby. The CDC says an undetectable viral load prevents HIV passing on during pregnancy, labor and delivery. The WHO says pregnant women with HIV should start treatment as soon as possible.

Tell your prenatal care team about the exposure, even if it feels awkward. They can plan the right tests at the right times.

Breastfeeding after a possible exposure

If you’re breastfeeding and may have been exposed to HIV, talk to a clinician as soon as you can. A very new infection may not show up on a test straight away, so CDC guidelines describe options to discuss with you:

  • stopping breastfeeding, or
  • pumping and storing your breast milk until HIV has been ruled out, then going back to breastfeeding.

This is a shared decision between you and your clinician, based on your situation and what matters to you.

PrEP while pregnant or breastfeeding

If you might be exposed again, ask about PrEP (pre-exposure prophylaxis). The CDC says PrEP can help prevent HIV while trying to conceive, during pregnancy and while breastfeeding. You’ll need a negative HIV test before you start.

Your testing plan

  • If you’re on PEP: tests at 4 to 6 weeks and 12 weeks after the exposure.
  • If you’re past 72 hours: an HIV test now, then a lab antigen/antibody test (blood from a vein) from 45 days after the exposure. See what to do after 72 hours.
  • If you get a fever, rash or sore throat in the weeks after the exposure, contact your clinician and ask for an HIV test.

HIV test accuracy by week explains when each kind of test gives a reliable answer.

What to do now

  1. Within 72 hours? Seek PEP now and say you’re pregnant or postpartum.
  2. Breastfeeding? Ask the same clinician about your options, including pumping and storing milk until HIV is ruled out.
  3. Tell your prenatal or postnatal team so they can plan testing.
  4. Book your follow-up tests, and ask about PrEP if you may be exposed again.