Reducing vertical HIV transmission: a story of success

Posted 12 Dec 2022

Date: 12 Dec 2022

Author: Helen Peters

Following on from World AIDS Day on 1 December, this month’s eFeature, written by Helen Peters – Manager of the Integrated Screening Outcomes Surveillance Service (ISOSS) – reflects on the success of antenatal screening and HIV treatment in reducing vertical HIV transmission.

Helen PetersOn the 1st December it was World AIDS Day – a great opportunity for us to reflect on how far we have come in the fight against HIV and AIDS and how we can continue to make progress. In the UK, alongside major successes such as meeting the UNAIDS’s global 90-90-90 treatment targets, we have achieved and sustained a rate of vertical HIV transmission (when HIV is passed on from a mother to her baby during pregnancy, labour or breastfeeding) at below 0.4% since 2012 among women who are known to be living with HIV during pregnancy.

As a part of the NHS Infectious Diseases in Pregnancy Screening programme (IDPS), commissioned by NHS England, the Integrated Screening Outcomes Surveillance Service (ISOSS) carries out surveillance of women (and their infants) who screen positive for HIV, syphilis or hepatitis B in pregnancy. ISOSS is delivered by a team based at UCL Great Ormond Street Institute of Child Health. NHS England have recently published the annual ISOSS HIV report which focuses on women who booked for antenatal care in 2020.

Screening in pregnancy

Screening for infections in pregnancy enables detection and treatment to significantly reduce the risk of vertical transmission of infection and to improve health outcomes for women and their babies.

In England, antenatal screening for HIV, syphilis and hepatitis B is offered and recommended to all women in every pregnancy, regardless of previous results or treatment. Uptake of screening remains high at 99.8% for all 3 infections in 2021 to 2022. Approximately 4,000 women will have a confirmed screen positive result each year for HIV, hepatitis B and/or syphilis, (or will be identified as having a prior diagnosis of HIV or hepatitis B) and will be referred into specialist care during pregnancy.

Surveillance of HIV in pregnancy

HIV surveillance of all pregnancies to women diagnosed with HIV, their babies and any children diagnosed with HIV has been undertaken in the UK for over 30 years. There are approximately 900 pregnancies to women living with HIV every year in the UK. In line with figures for all adults living with HIV nationally, around 90% of pregnant women living with HIV are already aware of their status before they become pregnant. Around 92% of these women are already on antiretroviral therapy when they conceive, and over 90% of deliveries are to women who have an undetectable viral load (the treatment they are taking is suppressing their HIV).

In addition to the role of the IDPS, the consistently low vertical transmission rate in the UK is a result of the effective treatments and interventions and well-established clinical pathways in line with the British HIV Association (BHIVA) and the Children’s HIV Association (CHIVA) guidelines.

Changing demographics

In recent years, we have noted some interesting changes in the demographics of pregnant women living with HIV. As in the general population, pregnancies to women of older age is increasing, with around 1 in 5 pregnancies now in women over 40. Whilst pregnancies to women born in sub-Saharan Africa have declined (from 72% in 2015 to 59% in 2020), we are seeing more pregnancies among women from Eastern Europe.

An important emerging group are those pregnant women who acquired HIV vertically themselves, with a 10-fold increase from 0.3% of in 2006-09 to 3.5% in 2018-21. As more women growing up with HIV reach reproductive age, their experiences and pregnancy outcomes continue to improve, although more work is needed to understand the specific challenges facing this group.

Pregnancy management

Most women are now already on treatment when they become pregnant and have undetectable viral loads throughout pregnancy. For the small number of women diagnosed for the first time in pregnancy following screening, treatment is starting earlier. As part of a drive to normalise the pregnancy journey, women living with HIV with suppressed viral loads can make more active choices such as being supported to have a vaginal delivery and in some cases to breastfeed (BHIVA guidelines). Now nearly half of women deliver vaginally (48% in 2020) and 6% of births were to women who were supported to breastfeed.

Monitoring vertical transmissions

For the very small number of children who acquire HIV vertically, ISOSS investigate the management and circumstances around transmission. These cases are then taken anonymously to a multidisciplinary Clinical Expert Review Panel, who identify likely timings of infections and discuss common themes, good practice points and missed opportunities.

Among 13 transmissions reported since 2020, 6 were to women who were diagnosed postnatally.

In over half of cases (7/13), there were complicating issues during pregnancy included safeguarding, mental health issues and insecure housing.

Contributing factors identified included women acquiring HIV during pregnancy/breastfeeding after an initial negative result. Among women aware of their diagnosis in pregnancy factors included poor adherence, late booking, no antenatal care and undisclosed breastfeeding.

Findings have highlighted the importance of sexual health awareness in pregnancy, including making sure it is understood that the negative result means negative at the point of testing and does not confer protection throughout pregnancy (‘negative now’) and urgent intrapartum screening for women presenting in labour without a screening result.

Looking forward

The comprehensive national surveillance carried out by ISOSS provides valuable insights that support the screening programme to ensure women and their babies get the best care possible. For example, we can see that the changes in the population of women living with HIV accessing antenatal care in the UK will have implications for services across the NHS.

Late booking for antenatal care, undisclosed breastfeeding and women acquiring HIV during pregnancy/breastfeeding are among drivers of transmission and therefore important to monitor, whilst investigating and addressing health inequalities remains a priority.

By working closely with our valued maternity, paediatric and sexual health colleagues across the country and with continued funding from NHS England, ISOSS is able to provide high quality, robust and timely data to support women and their babies by informing clinical guidelines and the NHS IDPS screening programme.


Published in the December 2022 edition of the Sexual Health, Reproductive Health and HIV Policy eBulletin.  The content of all eFeatures represents the views and opinions of the authors. FSRH and coalition partners do not necessarily share or endorse the views expressed within them.