Mother-to-child STIs transmission

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Pregnant women can contract a sexually transmitted infection (STI) just in the same way as non-pregnant women, but they also face an additional problem because some STIs can be transmitted to and infect the foetus or newborn if not treated at the right time. As such, it is important that the preventive measures described earlier are still used throughout pregnancy. The false sense of security that arises because there is no need to prevent an unwanted pregnancy may reduce the perception of risk, both in the pregnant patient and her sex partner, such that they relax the use of condoms.

Depending on the type of STI, the infection can be transmitted across the placenta during pregnancy, at the time of birth when the foetus comes into contact with vaginal secretions, or even after childbirth in breast milk, as is the case for HIV.

Newborns infected with some of these infections may present specific symptoms such as conjunctivitis (in the case of Chlamydia and Gonorrhoea, others could manifest a severe neonatal infection (genital herpes), others may pass undetected at delivery and later develop into a chronic infection (HIV, hepatitis B and C), and if some go undiagnosed and untreated, then they may have permanent physical and mental consequences for the baby (syphilis). Fortunately, transmission to the foetus and newborn can be prevented in most cases so long as the infection is diagnosed in the expectant mother and the appropriate treatment is administered.

Generally, the symptoms of STIs are the same in pregnant women as in non-pregnant women, although they are sometimes more obvious. Infections with a higher risk are those that do not present any symptoms. That is why pregnant women are indicated to undergo tests for certain STIs which could go undetected and may be transmitted to the baby.

It is particularly important that STIs are treated during the pregnancy because of the dual risk for mother and child. To avoid damaging the foetus, the treatments may differ from those used in non-pregnant women and so it is essential that patients do not self-medicate.

Infections with repercussions for the foetus or newborn


​​​​​​HIV. All women must carry out a HIV test during pregnancy. HIV infection can be transmitted to the newborn during pregnancy, at the time of delivery or through breast milk. There are currently some very effective measures available to prevent transmission to the baby. All pregnant women infected by HIV are recommended to follow combination antiretroviral therapy and maintain an undetectable viral load in blood for as long as possible. In the case of optimal infection control, vaginal birth is an option, although in certain situations a caesarean section is recommended. Breastfeeding is contraindicated in all cases of a HIV-infected mother. Pregnant women with HIV infection can present a higher risk of complications, consequently they should be managed by specialised units and in coordination with the doctor directing treatment for the HIV infection.

Liver and Hepatitis C virus

Hepatitis B and C. The possibility of hepatitis B infection must be studied in all pregnant women. It is mostly likely to be transmitted to the newborn during childbirth, although in some cases it occurs during pregnancy. The newborn has to be treated and administered the first dose of a vaccine within a few hours of birth to avoid becoming infected. Some women may also require treatment during the third trimester of the pregnancy to prevent infecting the baby or for their own health. Hepatitis C infection must be ruled out during pregnancy in women who present certain risk factors (a tattoo or piercing, drug users, recipient of a blood transfusion or transplant in the past, partner infected with hepatitis C, liver dysfunction). Hepatitis C is transmitted to the baby in approximately 3% of cases. There are treatments that can cure the infection if administered after childbirth.

Pubic irritation in a woman

Syphilis. A syphilis test must be carried out at least once during all pregnancies or every trimester in high-risk cases. Besides affecting the mother, syphilis can be transmitted to the unborn baby during pregnancy and result in congenital syphilis. Congenital syphilis can lead to miscarriage or foetal death, or potentially cause certain malformations and intellectual disability in the newborn. More active cases of syphilis present a greater risk of harming the baby. A very effective treatment is available for both the mother and foetus which prevents or cures congenital syphilis. Pregnant women who test positive for syphilis and have not been treated previously must receive treatment during the pregnancy. Patients should use a condom and their sexual partners be tested for syphilis to prevent reinfection.

Genital herpes in women

Genital herpes. Pregnant women with a history of genital herpes infection often suffer from a new episode (recurrence) at some point in the pregnancy. The virus can be transmitted to the newborn during childbirth, particularly in cases in which the first episode of herpes occurs at the time of delivery or in the preceding weeks. The newborn’s infection could be very severe and appear a few days after birth, manifesting with skin lesions, eye lesions or central nervous system compromise. A caesarean section can protect the baby from infection and so they are recommended if herpes lesions are present at the time of delivery and in women who were first infected in the last few weeks of the pregnancy. Pregnant women affected by an episode of genital herpes (either the first or a recurrence) are treated throughout the final weeks of pregnancy and up until childbirth to ensure they are herpes-free at the time of birth and vaginal delivery is therefore a safe option. 

As for all women, the use of condoms is recommended to prevent sexual transmission from the onset of any discomfort until the ulcers have been cured and particularly if their sexual partner presents lesions.

Symptoms of gonorrhoea in a man

Chlamydia and gonococcal infection. Both infections can go undetected in women, including during pregnancy. Apart from the possible complications this can imply, both infections may also be transmitted to the newborn during childbirth, primarily causing a potentially very severe eye infection and sometimes a lung infection in the case of Chlamydia or a systemic infection for gonococcal infection. All newborns should be treated with an eye ointment immediately after childbirth to prevent eye infections, regardless of whether it was a vaginal or caesarean delivery. Furthermore, many pregnancy monitoring protocols recommend screening for these two infections using a sample of vaginal discharge in the first and third trimesters in at-risk expectant mothers (under 25 years old, sexually promiscuous, recent change of partner, etc.) so those who test positive can be treated.

Female reproductive tract and human papilloma virus

Human papillomavirus (HPV). HPV infection may be more apparent during pregnancy and infected women often present genital warts or condylomas, or these grow and become more visible. Condylomas sometimes disappear spontaneously after childbirth. HPV infection is considered low risk for both the foetus and the newborn, the pregnancy can be managed according to normal protocols and a vaginal delivery is possible even when condylomas are present. A caesarean section is only indicated if the condylomas are bleeding or large enough to interfere with delivery. If the genital warts grow, bleed or cause discomfort they can be treated during pregnancy but many of the usual creams should be avoided and it is better to remove them with laser treatment or by applying a cold compress. A condom should be used whenever condylomas are present.

Women with a cancer or precancerous lesion caused by HPV (diagnosed by histology or biopsy) should see a gynaecologist before becoming pregnant.

The HPV vaccine and pregnancy

The HPV vaccine is contraindicated during pregnancy. If a pregnant woman needs to be given a dose of vaccine it is better to delay it until after the delivery. In any event, there is no need to worry if you accidentally receive the vaccine while pregnant or are vaccinated shortly before becoming pregnant because it has not been associated with any adverse effects or defects in newborns.

Substantiated information by:

Irene Fuertes De Vega
José Luis Blanco Arévalo
Mercè Alsina Gibert
Núria Borrell Iragari

Published: 20 February 2018
Updated: 20 February 2018

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