Why you were tested at all

Hepatitis B is one of three infections screened for in every pregnancy in England through the NHS Infectious Diseases in Pregnancy Screening programme, alongside HIV and syphilis. The programme overview says healthcare professionals "should offer and recommend screening to all pregnant women as part of their antenatal care", with a blood test "as early as possible in pregnancy to ensure timely referral and management of care".

Prevalence is low and very unevenly distributed. The IDPS handbook reports that hepatitis B prevalence in the pregnant population in England varies "from 0.05% to 0.08% in some rural areas, rising to 1% or more in certain inner-city areas". Those are English maternity population figures, not global ones. WHO's global picture is different again: it estimates 240 million people living with chronic hepatitis B in 2024, with the highest burden in the Western Pacific and African Regions.

What happens after a positive result, and how fast

The UK pathway is unusually specific about timeframes, which makes it easy to check whether your care is on track.

Screening results should be available to maternity services "within 8 working days" of the sample reaching the laboratory.
You should be offered an appointment to discuss a confirmed positive result "in less than or equal to 5 working days" of the maternity service being notified, with the day of notification counted as day 1.
"All women with a new diagnosis of hepatitis B in pregnancy should be seen within 6 weeks regardless of their infectivity status."

An inconclusive result is handled differently: a repeat sample is taken at least 2 weeks after the first, and the handbook says that to avoid unnecessary distress, referral to specialist services is not recommended unless the repeat confirms infection.

Higher and lower infectivity: what the second round of tests is for

After a positive screening result, further tests determine your infectivity level, using HBeAg and anti-HBe status together with your hepatitis B viral load.

Higher infectivity means a positive HBeAg, negative anti-HBe status, or a high viral load. The IDPS handbook says you should be seen by specialist hepatitis B services within 6 weeks of the maternity service receiving your positive result, and that all babies born to women in this group require hepatitis B immunoglobulin in addition to the vaccine.

Lower infectivity means a negative HBeAg and positive anti-HBe status with a viral load below 2x10⁵ IU/ml. Here the handbook says you should be seen by specialist hepatology services within 18 weeks, and that babies require vaccination only.

There is one wrinkle the handbook flags directly. Women with a viral load at or above 2x10⁵ IU/ml may be offered antiviral medication in the third trimester to reduce the amount of virus present at birth, and the handbook notes that "this is lower than the threshold for infants who require HBIG, meaning some women may require treatment in pregnancy but their infants will not require HBIG". Those are two different thresholds doing two different jobs, and confusing them is easy. This page names the treatment and gives no dose.

What the risk to your baby actually is

The IDPS handbook is direct about the untreated figures, and they are why the pathway exists. Without intervention, the risk of a baby acquiring hepatitis B at birth "can be as high as 90% for women with higher infectivity level, and between 10% to 40% for women with lower infectivity". And whereas around 90% of adults who newly acquire hepatitis B clear it, "90% of infants who acquire hepatitis B vertically will develop chronic infection", which carries an increased lifetime risk of liver cancer.

Those are the untreated numbers. With the pathway in place, the handbook describes high antenatal screening coverage plus a timely birth dose of vaccine as "the most effective method of preventing vertical transmission". A birthweight exception applies: babies weighing 1500 g or less receive immunoglobulin as well as vaccine regardless of maternal infectivity status.

What does not change

This is the sentence most people are looking for, and the handbook says it plainly: "a woman's hepatitis B status should not impact decisions about delivery or choice of infant feeding."

You can have a vaginal birth. You can breastfeed. Neither is restricted by hepatitis B, and if you are told otherwise it is worth asking which guidance that advice comes from.

Your own health, beyond the pregnancy

It is easy for a hepatitis B diagnosis found in pregnancy to be treated entirely as a baby-protection exercise. The handbook is clear that chronic infection carries an increased risk of cirrhosis and liver cancer and that management should be by a hepatologist or gastroenterologist, so the referral is for you as well as for your baby. Make sure the follow-up continues after birth rather than stopping at discharge.

Household and sexual contacts should be offered testing and vaccination. The NHS pages on hepatitis B describe the infection, its transmission routes and its long-term management, and are a reasonable thing to share with family.

Elsewhere

ACOG's 2023 clinical practice guideline on viral hepatitis in pregnancy sets out the US approach, which also involves universal screening in pregnancy and infant immunoprophylaxis. WHO recommends testing all pregnant women in order "to provide the opportunity to institute measures for prevention of mother-to-child transmission". The national pathways differ in the details of thresholds and timing, so if you have been treated in more than one country, expect the specifics to differ without either being wrong.

Hepatitis B in Pregnancy