Prevention of Prenatal Infectious Disease

Sick baby sleeping in NICU bed with oxygen monitor and head bandages

(Adobe Stock 580421099 by Leslie Rodriguez)

Every woman who becomes pregnant should be aware that her personal health decisions will play a critical role in the health of her fetus. In fact, the first 1000 days of a child’s life (from conception to the child’s second birthday) are thought to be the time required to ensure that the child will be healthy and develop properly. During those 1000 days, the mother’s diet will be important and affect fetal health.¹

However, nutritional health for a newly pregnant mother is not the only thing that she should be concerned about. There are lifestyle choices she must make even before she becomes pregnant to help provide a developing embryo and fetus with the best chances at a safe pregnancy. When mothers do not follow basic rules regarding their lifestyles, their newborns may have a low weight at birth. These neonates with low birth weight are 5 times more likely to die than neonates of mothers who follow prenatal guidelines.²

Table 1. List of Measures a Pregnant Woman Can Follow to Help Ensure the Birth of a Healthy Neonate³

Credit: Author

For many pregnant mothers, information to help them provide the best conditions for their developing fetus may come from a basic self-help list. One such list from the Eunice Kennedy Shriver National Institute of Child Health and Human Development in the National Institutes of Health provides guidelines that include 11 items she should follow for a healthy pregnancy (Table 1).³ Many of these self-help lists focus on fetal prenatal care from the perspective of the mother’s lifestyle. Items she must consider include things to do and things not to do related to diet, exercise, alcohol consumption, and smoking.

For example, the mean gestational age at birth of neonates of women who smoked and drank heavily was found to be significantly lower than that of neonates of women who did not smoke or drink during pregnancy (267 vs 274 days; P < .01).⁴ A pregnant mother should consider developing a plan for regular prenatal care from an experienced health care provider. These caregivers can include obstetricians, family practice physicians, or a certified nurse-midwife or certified professional midwife.⁵ If a newly pregnant woman follows these guidelines, is that all she should be concerned about?

As noted in Table 1, the last entry points show the need for a pregnant woman to be careful not to become infected by a pathogen while carrying her fetus. A pregnant woman is susceptible to infection by various pathogens. Vaginal yeast infections are relatively common during pregnancy but usually cause no complications. Other infections by pathogens can include the usual list of suspects: bacteria, viruses, fungi, and parasites. The source of these pathogens can be from other individuals, insect bites, contact with animals, airborne exposure, contaminated food or water, or sexual contact. Many such infections during pregnancy may be harmless to the developing fetus. However, some may cause premature birth, low birth weight, congenital disabilities, learning problems, and possible loss of the fetus.⁶ Physicians treating a pregnant woman infected by bacterial pathogens have limited choices in their response due to the impact that certain drugs (eg, antibiotics) may have on the developing fetus.⁷

Table 2. List of Infectious That Can Cause Damage to a Fetus^7-11

Credit: Author

Infections linked to problems during pregnancy include many pathogens such as bacteria, viruses, yeasts, and some protozoa (Table 2^7-11). Sexually transmitted pathogens, such as those that cause chlamydia and gonorrhea, can result in conjunctivitis or pneumonia in a neonate.⁷ If gonorrhea is transferred to the neonate’s eyes as they pass through the birth canal, blindness can result. Numerous viral pathogens can cause serious problems for a developing fetus.

One well-known virus, the Zika virus, affects pregnancy and caused a great deal of concern in the US in 2015 and 2016 when an outbreak of the mosquito-borne virus occurred. It is estimated that 5% of pregnant women infected by the Zika virus had fetuses with brain abnormalities, with the most common being microcephaly (smaller than normal head size).¹¹

More likely, problems associated with viral infections will be caused by
cytomegalovirus (an estimated 60% of women in developed countries are infected by this virus), which can result in neonatal hearing loss. Infection by rubella virus can result in spontaneous abortion or stillbirth. HIV infection of a developing fetus is much less common than it once was, but it can still cause major problems for neonates. As of 2015, the rate of transfer of HIV from infected mothers to their fetuses decreased to less than 1%, but any fetus that contracts the virus will have HIV positivity as a neonate, and the disease can later progress to AIDS.

Infection by the influenza virus in pregnant women has been linked to an increased risk of pregnancy complications.⁹ Many other types of viral infection have been linked to lowered incidence of survival for neonates.

During pregnancy, bacterial urinary tract infections (UTIs) are more common than in the general population. Pregnant women with UTIs are often asymptomatic, requiring periodic screening of urine for possible positive culture results.

Generally, levels of pathogens in the urine must be higher than 105 colony-forming units for many pathogens and lower if group B Streptococcus (GBS) is observed for preventive measures to be recommended.7 The gastrointestinal and genital tracts of an estimated 18% of women worldwide have GBS colonization. If a prenatal infection due to GBS occurs, the outcome can be maternal death, stillbirth, or neonatal death.¹² In fact, infection by GBS is the leading cause of life-threatening bacterial infections in neonates.¹³ Antibiotics are generally prescribed for a pregnant mother if any GBS is detected in her urine. However, care must be given to the type of antibiotic used (eg, penicillins and cephalosporins are generally considered safe during pregnancy, whereas tetracyclines should be avoided).

Suppose the use of antibiotics to manage bacterial infections in a pregnant woman is potentially hazardous to her developing fetus. Are there any other proactive treatments that may help reduce the impact of infection on neonates? In addition, because antibiotics do not target viral pathogens, is there anything that can be done to help reduce fetal pathologies due to viral infection in pregnant women?

The obvious answer to both questions is through vaccination. There is abundant evidence that developing fetuses receive antibodies from their mothers transplacentally (and later via breast milk) in a version of passive immunity. Thus, if bolstered through vaccination to include resistance to many common pathogens that can harm a fetus, the mother’s antibody reserves can help give the neonate a much greater chance of surviving infections. In findings from a study of the cost-effectiveness of a vaccine against GBS in pregnant women in Japan, where costs associated with the treatment of neonates infected by GBS in utero were compared with the cost of the vaccine (estimated to be $35 per dose), the use of this vaccine was found to be highly cost-effective. Additional benefits from using this vaccine may be seen through other perinatal outcomes.¹³ Another study about vaccine efficacy against a bacterial infection in pregnant mothers focuses on the tetanus, diphtheria, and pertussis (Tdap) vaccine (against Bordetella pertussis, which causes whooping cough). The Tdap vaccine has been found to be safe for both the mother and the developing fetus.¹⁴

For viral infections in pregnant women, vaccines can also help reduce the impact of infection on fetal health. Viral vaccines against influenza and SARS-CoV-2 have been found to be safe and effective at reducing the chance of fetal infection by those viruses.¹⁵ Other vaccines for viruses such as rubella (eg, the measles, mumps, and rubella vaccine) that involve a live virus are not recommended for pregnant women. As new vaccines for viral and bacterial pathogens that pose a risk to mothers and their developing fetuses are produced, there are many agencies considering their safety. Hopefully, new vaccine regimens will become available to women who are considering becoming pregnant and provide their developing fetuses with the best possible protection against infection via passive immunity.

Overall, any woman considering pregnancy should consider all the precautions recommended in Table 1. As they develop a relationship with their caregiver, they will hopefully discuss healthy lifestyles that will include measures to help them avoid infection by pathogens that could lead to an undesirable outcome for their pregnancy.

References

1. Baker SK. 1000 days of good nutrition: in the United States or abroad, it is about equity, evidence, and leadership. Am J Public Health. 2022;112(S8):S776-S778. doi:10.2105/AJPH.2022.307077
2. Pregnancy care. Healthline. Accessed December 21, 2023. https://www.healthline.com/health/pregnancy-care
3. What can I do to promote a healthy pregnancy? Eunice Kennedy Shriver National Institute of Child Health and Human Development. Accessed December 21, 2023. https://www.nichd.nih.gov/health/topics/preconceptioncare/conditioninfo/healthy-pregnancy
4. Odendaal HJ, Kruger M, Botha MH. Dangers of smoking cigarettes and drinking alcohol during pregnancy. S Afr Med J. 2020;110(11):1066-1067. doi:10.7196/SAMJ.2020.v110i11.14738
5. Prenatal care and tests. Office on Women’s Health. Accessed December 17, 2023. https://www.womenshealth.gov/pregnancy/youre-pregnant-now-what/prenatal-care-and-tests
6. Ledan S. Infectious diseases in pregnancy. U.S. Pharmacist. September 16, 2020. Accessed December 17, 2023. https://www.uspharmacist.com/article/infectious-diseases-in-pregnancy
7. Leeper C, Lutzkanin A III. Infections during pregnancy. Prim Care. 2018;45(3):567-586. doi:10.1016/j.pop.2018.05.013
8. Friel LA. Infectious disease in pregnancy. Merck Manual Professional Version. Accessed December 21, 2023. https://www.merckmanuals.com/professional/gynecology-and-obstetrics/pregnancy-complicated-by-disease/infectious-disease-in-pregnancy
9. Silasi M, Cardenas I, Kwon JY, Racicot K, Aldo P, Mor G. Viral infections during pregnancy. Am J Reprod Immunol. 2015;73(3):199-213. doi:10.1111/aji.12355
10. Mesini A, Saffioti C, Mariani M, et al. First case of Candida auris colonization in a preterm, extremely low-birth-weight newborn after vaginal delivery. J Fungi (Basel). 2021;7(8):649. doi:10.3390/jof7080649
11. Pregnancy. CDC. Accessed December 21, 2023. https://www.cdc.gov/zika/pregnancy/index.html
12. Seale AC, Bianchi-Jassir F, Russell NJ, et al. Estimates of the burden of group B streptococcal disease worldwide for pregnant women, stillbirths, and children. Clin Infect Dis. 2017;65(suppl 2):S200-S219. doi:10.1093/cid/cix664
13. Sorano S, Procter SR, Seale AC. Cost-effectiveness analysis of maternal vaccination against group B Streptococcus in Japan. Vaccine X. 2023;14:100332. doi:10.1016/j.jvacx.2023.100332
14. Whooping cough vaccines are safe. CDC. Accessed December 21, 2023. https://www.cdc.gov/pertussis/pregnant/mom/safety-side-effects.html
15. Vaccine safety for moms-to-be. CDC. Accessed December 21, 2023. https://www.cdc.gov/vaccines/pregnancy/vacc-safety.html