Genital herpes during pregnancy

By trimester

Weeks 1–13

1st trimester

Tell your provider about any herpes history at your first prenatal visit, even without a current outbreak, and share your partner's history too, since that shapes counseling on precautions like condom use.

Weeks 14–27

2nd trimester

A first-ever (primary) infection during pregnancy carries the highest risk to the baby and needs prompt medical care. A recurrence of a herpes history you already had before pregnancy is a much lower concern at this stage.

Weeks 28–birth

3rd trimester

Suppressive antiviral medication, typically acyclovir or valacyclovir starting around week 36, is standard for anyone with a herpes history to reduce the chance of an outbreak at delivery. A C-section is usually recommended only if you have active lesions or prodromal symptoms when labor starts.

What does the evidence show for genital herpes?

• Newborn infection risk depends heavily on timing: about 1 out of 100 babies became infected during childbirth when the mother's herpes infection occurred before or early in pregnancy, compared with 30 to 50 out of 100 when infection first occurs in the last trimester. 1
• Suppressive antiviral therapy lowers the cesarean rate for people with a herpes history, with cesareans occurring in 13 out of 100 untreated women versus 4 out of 100 who received suppressive therapy, and studies of acyclovir haven't found evidence that it harms the baby. 1
• In a suppressive acyclovir trial starting around week 36, only 1% of compliant patients had a clinical recurrence at delivery, compared with 18 to 37% in historical controls who didn't take suppressive therapy, and no significant maternal or fetal side effects were observed. 2
• The reason a recurrent outbreak is so much lower-risk than a first infection is maternal antibodies: a pregnant woman who already had HSV before pregnancy has circulating IgG antibodies that cross the placenta and protect the fetus, keeping transmission risk to 2 to 5% with visible lesions and under 0.05% without symptoms, versus 30 to 50% for a first-episode infection late in pregnancy. 3
• Neonatal herpes is classified into three patterns of increasing severity: skin-eyes-mouth disease (45% of cases, lower mortality but recurs in 90% of patients), central nervous system disease (30%), and disseminated disease affecting multiple organs (25%, the most severe, with death often from liver failure or respiratory failure), which is far more serious than a typical adult outbreak. 4

When should I call my provider about genital herpes?

A first-ever genital herpes outbreak anytime in the third trimester is the highest-risk scenario for the baby and needs prompt antiviral therapy and close coordination with your delivery team, since it can raise newborn transmission risk to 30 to 50 percent versus about 1 percent for infection earlier in pregnancy. Active lesions or prodromal symptoms (tingling, pain) when labor starts are the main reason providers recommend a cesarean instead of vaginal delivery. Any signs of neonatal herpes after birth, such as skin blisters, lethargy, poor feeding, or fever in the first weeks of life, need emergency evaluation, since untreated neonatal HSV can rapidly become disseminated or affect the brain. Trust your read on your own body. If something feels off beyond the list above, please consult your healthcare provider rather than waiting it out.