Sexually transmitted diseases (STDs) pose a significant health challenge during pregnancy. An infection present in a pregnant individual can directly threaten the developing fetus or the newborn baby. These pathogens can cause complications, including premature birth, low birth weight, and long-term health issues or developmental differences in the child. The mechanism by which an infection is passed from the parent to the child is known as vertical transmission.
Understanding how these infections move from the parent to the baby is central to preventing adverse outcomes. The specific timing of transmission dictates the potential severity of the resulting condition. Some infections impact the fetus early in development, while others pose a risk primarily during the birthing process itself.
How STDs Transmit to the Fetus or Newborn
Infections reach the developing baby through three primary routes, defined by the timing of exposure. The first is transplacental transmission, where the pathogen crosses the placental barrier during gestation. This allows the infection to enter the fetal bloodstream and organs directly while the baby is still in the uterus. Infections utilizing this route can cause widespread damage to developing organ systems, often leading to severe congenital differences.
The second and most common route is perinatal, or intrapartum, transmission, occurring during the delivery process. As the baby passes through the birth canal, they are exposed to maternal blood, genital secretions, and infected lesions. Pathogens like Herpes Simplex Virus, Neisseria gonorrhoeae, and Chlamydia trachomatis are typically acquired this way, leading to infections that manifest shortly after birth.
A third, less frequent pathway is postnatal transmission, occurring after birth. This can happen through direct contact with active lesions or through bodily fluids, such as breast milk, for certain viruses. Although the risks are usually lower than with the other two routes, the precise moment of transmission is determined by the specific organism and its ability to penetrate biological barriers.
Specific Infections and Associated Birth Outcomes
Syphilis
Syphilis, caused by the bacterium Treponema pallidum, is concerning because it crosses the placenta and causes congenital syphilis. Untreated primary or secondary syphilis carries a significant risk; approximately 40% of babies born to affected mothers are stillborn or die shortly after birth. The systemic nature of the infection in the fetus can damage multiple organ systems.
Babies with congenital syphilis may develop skeletal deformities, such as a flattened nasal bridge (“saddle nose”) or abnormal bone thickening of the shins (“saber shins”). Late-stage manifestations, often appearing after two years, include dental abnormalities (Hutchinson teeth), progressive sensorineural deafness, and interstitial keratitis, which can lead to blindness. The infection can also result in neurological problems, including meningitis, seizures, and developmental delay.
Herpes Simplex Virus (HSV)
Herpes Simplex Virus (HSV), typically HSV-2, is usually transmitted perinatally during delivery when the infant contacts active genital lesions or infected secretions. Neonatal herpes is a serious condition, and the risk is highest when the mother acquires a primary HSV infection late in pregnancy. While rare, some cases are acquired in utero, leading to congenital HSV infection with outcomes like microcephaly and ocular issues.
Neonatal herpes can manifest as localized disease affecting the skin, eyes, and mouth, or progress to more serious forms. Disseminated infection involves multiple organs, including the liver and lungs, and carries a high mortality rate. The most severe outcome is central nervous system (CNS) disease, which results in herpetic encephalitis, seizures, and permanent neurological disability.
Hepatitis B
The Hepatitis B virus (HBV) is primarily transmitted during the birthing process through exposure to maternal blood and fluids. Most newborns infected with HBV are asymptomatic at birth but have a high likelihood of developing a chronic infection. Without immediate intervention, up to 90% of infants infected around birth will develop chronic Hepatitis B.
This chronic infection can lead to long-term liver complications later in life, even if the child remains symptom-free for years. These complications include cirrhosis (scarring of the liver) and an increased risk of developing liver cancer. Preventing this chronic state requires immediate intervention at delivery.
Gonorrhea and Chlamydia
Both Neisseria gonorrhoeae (Gonorrhea) and Chlamydia trachomatis (Chlamydia) are bacterial infections transmitted to the newborn during passage through the birth canal. These organisms typically cause localized infections rather than widespread congenital differences. The most common outcome is ophthalmia neonatorum, a severe conjunctivitis that develops shortly after birth.
Gonococcal ophthalmia neonatorum is a rapidly progressive infection that can lead to corneal ulceration and permanent visual impairment if untreated. Chlamydia infection is commonly associated with pneumonia in the infant, occurring in 10% to 20% of exposed newborns, in addition to causing conjunctivitis. These infections can often be prevented with timely prenatal treatment.
HIV
The human immunodeficiency virus (HIV) can be transmitted during pregnancy, delivery, or after birth through breastfeeding. The primary concern is the infant acquiring the virus, which compromises the immune system and leads to acquired immunodeficiency syndrome (AIDS). The risk of transmission is dramatically reduced with modern medical management.
Infants who acquire HIV face a weakened immune system, making them susceptible to opportunistic infections and developmental delays. Current protocols aim to maintain a low or undetectable viral load in the pregnant person, which significantly lowers the risk of transmission.
Prenatal Screening and Mitigation Strategies
Screening and intervention protocols manage the risks associated with STDs during pregnancy. Routine prenatal care involves testing all pregnant individuals for Syphilis, HIV, and Hepatitis B during the first prenatal visit. Screening for Chlamydia and Gonorrhea is also recommended for all pregnant people under 25 years old and those at increased risk.
For bacterial infections, such as Syphilis, Gonorrhea, and Chlamydia, antibiotic treatment is highly effective at eliminating the infection and preventing vertical transmission. Treatment for Syphilis with penicillin has an efficacy of approximately 98% in preventing congenital syphilis when administered early. Individuals at high risk often receive repeat screening for Syphilis and HIV in the third trimester to catch new infections.
Mitigation strategies during delivery are tailored to the specific infection. For a pregnant person with active genital herpes lesions at labor, a Cesarean section is often recommended to prevent the baby from contacting the virus. In cases of HIV, the parent receives antiretroviral therapy (ART) throughout pregnancy, and the newborn is given prophylactic medication immediately after birth. For Hepatitis B, the newborn receives the Hepatitis B vaccine and Hepatitis B Immune Globulin within hours of birth, which prevents chronic infection.