Infections in Pregnancy: Prevention, Causes and Treatment

Bacteria, parasites and viruses are everywhere.

Our bodies are normally colonized with a multitude of different organisms that we live with in harmony every day. Infection is very different than colonization, and infection results when either an overgrowth of an organism occurs due to an imbalance in the local flora, or when a natural barrier of the body, such as skin, respiratory tract or GI tract is invaded by a foreign organism. Infections can be mild and transient or severe and life threatening.

We certainly have a better handle on bacteria than we do on viruses, which despite advances in modern medicine, cure remains elusive, such as with the HPV, HIV and the herpes simplex virus. Infections in pregnancy take on an even more significant role, as our concern extends to both mother and fetus. Despite the fact that the fetus lives in a protected sterile environment within the uterine cavity, infectious organisms may access this sterile cavity through the maternal bloodstream, and cross the maternal-fetal barrier through the placenta, therefore infecting the fetus as well as the mother.

Fetal infection can lead to serious, long lasting sequelae and even death. Moreover, infections in pregnant women may be more severe than in non pregnant women due to the fact that pregnancy results in a state of immunosuppression in the mother. Some things in life we can’t prevent, but other risks can be mitigated by knowledge and precautions. This article will highlight some of the infections that we see in pregnancy and how these infections are acquired. Once we identify the route of transmission we can then talk about prevention, and if that fails, how to provide treatment.


Infuenza or “the flu” occurs in a seasonal fashion, usually between the months of October and May, and usually presents with high fever, muscle aches, sore throat, and cough. The flu is very contagious and is spread by respiratory droplets and contact. The majority of patients who acquire the flu have a self limited disease and improve within in a week. Some patients can have more significant sequelae and some patients wind up with pneumonia or a more virulent course and in some cases the flu can lead to death.

The very young and the very old, patients who are immunocompromised, and pregnant women are most likely to have severe sequelae. Prevention cannot be guaranteed, but to decrease transmission, hand washing is a prerequisite, and making sure that people who are sick with fever, especially those who have been diagnosed with the flu should stay home from work until they are no longer ill. In addition, vaccination yearly with the inactivated flu vaccine is of paramount importance in the general population, especially in high risk groups such as pregnant women.

Pregnant women who get the flu have a higher chance of developing pneumonia, winding up in the intensive care unit setting, and of dying. This has been the case with a disproportionate amount of pregnant women dying in flu pandemics such as the last one in 2009. The flu vaccine is inactivated and not a live vaccine, and is therefore totally safe to administer at any time in pregnancy (pregnant women cannot have any live or live-attenuated vaccines, so only the inactivated injectable one is appropriate in pregnancy. There are no birth defects or fetal sequelae from the flu vaccine.

The American College of Ob/Gyn strongly encourages women in any trimester of pregnancy to get vaccinated against the flu if they will be pregnant during flu season. Many women are concerned about Thimerosol, a mercury containing preservative used in multi dose vials of the flu vaccine is not an issue and has never been demonstrated to cause fetal issues, and the ACOG does not recommend withholding the flu vaccine from pregnant women if it contains thimerosol, but because of theoretical concerns, we offer pregnant women thimerosol free flu vaccines. If this is not available, still take the vaccine in pregnancy- it is much more dangerous to not get vaccinated and contract the flu in pregnancy.

Tamiflu, is the antiviral medication that is used for both prophylaxis to prevent contracting the flu in individuals who have been exposed, as well as for those who have documented disease, is completely safe in any trimester of pregnancy, and should absolutely be used for pregnant women exposed to and who have contracted the flu.


CMV or cytomegalovirus is a viral infection that occurs commonly in young children. It is transmitted by blood and body fluids (blood, saliva or urine) or by sexual contact. Most patients have no symptoms, but some experience a mononucleosis type illness (ACOG practice bulletin number 20, September 2000). CMV is the most common congenital infection (an infection the baby contracts from the mother) and is the most common cause of congenital hearing loss.

Other findings in babies that contract CMV in utero include jaundice, growth restriction, an enlarged liver and spleen and brain issues. It is often diagnosed after the pregnant woman has abnormal ultrasound findings which may include calcium deposits on the fetal liver and brain, echogenic bowel, enlarged liver and spleen and enlarged ventricles in the fetal brain.

The risk of infection with CMV is greatest later in pregnancy, but the infection and sequelae are more severe if it occurs earlier in the pregnancy. When a mother contracts CMV for the first time in pregnancy, there is a 30-40% chance that the baby will catch it. Of those babies that catch CMV in utero 10% will show signs of it at birth and develop problems. 30% of severely infected infants die and 80% of the survivors have severe neurologic problems due to the infection.

Prevention of CMV is especially important for health care workers and child care workers who are exposed to blood and body fluids. Universal precautions are mandatory, and wearing gloves, gowns and eye protection is a must when handling or coming into contact with blood and body fluids. There is no vaccine available against CMV and no known cure.


Toxoplasmosis is a parasitic disease that humans can contract. Infection of a pregnant woman can cause fetal transmission that can have very significant sequelae.

Humans can get toxoplasmosis by eating undercooked meat, by contact with cat feces where the oocysts of toxoplasmosis reside, and by having contact with toxoplasmosis in soil. Patients can present with symptoms of lymph node swelling, fever, night sweats, muscle aches and an enlarged spleen and liver. The later the pregnant woman contracts toxoplasmosis, the more likely it is to be transmitted to the fetus, but the earlier the fetus is infected, the more severe the infection is.

A large number of babies who contract toxoplasmosis in utero will develop chorioretinitis which can lead to blindness, hearing loss, or mental retardation. Prevention of toxoplasmosis includes eating meat well done and not rare, not allowing the pregnant woman to come into contact with cat feces (someone else should change the litterbox), and pregnant women should not garden in the soil without gloves on.

Pregnant women should not drink unfiltered water and they should make sure to wash all fruits and vegetables before eating them.There is no vaccination available for toxoplasmosis, but if it is found that a pregnant woman has a blood test that suggests she was infected, confirmation should be done to make sure it is not a false positive (send the blood to a specialized reference lab in Palo Alto California), and if she is truly infected, treatment of the pregnant woman with an antibiotic called Spiramycin can reduce the chance that the fetus will become infected (by about 60%) and that those serious sequelae will ensue.

Spiramycin is only used to reduce the chance of transmission of toxoplasmosis from an infected mother to her baby, but if it is found that the baby actually has a true infection with toxoplasmosis treatment with pyrimethamine, sufonamides and folinic acid is necessary to add to the regimen (Page 958, 2014 Compendium, practice bulletin number 20, September 2000).


There has been a very big push from the CDC (Center for Disease Control) and ACOG to vaccinate all women who are pregnant against pertussis. Pertussis, also known as whooping cough, is a severe respiratory infection that can occur at any age, but is particularly dangerous in babies and can lead to death.

There have been recent outbreaks of pertussis, and all individuals who will have close contact with the baby should be vaccinated. Pregnant women can be vaccinated at any time in pregnancy because the vaccine is inactivated and safe in pregnancy and it is usually given routinely between 28 and 32 weeks. Husbands, grandparents and siblings should also be vaccinated as well.

Even in women who have an up to date DPT (diptheria, pertussis, tetanus) shot, another vaccine for pertussis should be given with each pregnancy to make sure that immunity persists.


Varicella, or chicken pox, is a highly contagious virus that is transmitted by respiratory droplets or by close contact with an infected individual. The incubation period is 10-20 days and patients can transmit the disease 48 hours before the rash appears, and are still infectious to others until all of the skin lesions have completely crusted over. (page 954 compendium 2014).


The symptoms of chicken pox include fever and a rash that turns into vesicles on the skin which are small fluid filled blisters.

The disease is usually very benign in children, but is much worse in adults and can lead to brain infection (encephalitis), pneumonia, and even death. Pregnant women, because of their compromised immune systems, are particularly at risk of severe complications, and the virus can cross the placenta, leading to fetal infection which can be devastating.

When a fetus contracts varicella in the first 20 weeks of pregnancy they can get “congenital varicella syndrome” which can lead to skin scarring, limb defects, eye problems and brain problems. Only 1-2% of fetuses whose mothers contract varicella in pregnancy actually get this syndrome, but for the ones that do, the results can be very severe. If a mother contracts varicella 5 days before delivery up until 48 hours after birth, a baby can have “neonatal varicella infection” that has a high rate of death. Many women have contracted chicken pox as a child and have natural immunity.

Once you get chicken pox you cannot get it again. The varicella virus lives dormant in the body and can reactivate into herpes zoster, also known as shingles. You cannot catch shingles from someone else, but if you are pregnant and not immune to varicella, you should not come into direct contact with the lesions of shingles because from that you could contract chicken pox. If you are not immune to chicken pox you should stay away from people who do have chicken pox, as it is very contagious and can be very serious for mother and baby.

Another important way to protect yourself and your baby against varicella in pregnancy is to receive a varicella vaccine AT LEAST 3 MONTHS PRIOR to getting pregnant. The varicella vaccine is a live vaccine and cannot be given in pregnancy and ideally one should not get pregnant for 3 months after receiving the varicella vaccine.

If you did not have chicken pox as a child or if you are unsure, and you did not receive the vaccine, and are thinking of becoming pregnant in the next few months, talk to your doctor about getting blood drawn to see if you have immunity to varicella. If you do, there is nothing to worry about. If you don’t, then you can be proactive and get vaccinated.

If a pregnant women who is not immune to varicella comes into contact with someone who has chicken pox, she should be given VZIG ASAP, but particularly within 72 hours of exposure. This will help to ameliorate the maternal effects, but will not prevent fetal infection.


Treatment for varicella involves giving the mother oral acyclovir, preferably within 24 hours of getting the rash. Oral acyclovir is safe in pregnancy. If the mother has complications of varicella such as pneumonia or encephalitis, she should be hospitalized and given IV acyclovir. The acyclovir helps the mother, but won’t prevent complications in the baby. When the baby is born it should receive VZIG (varicella zoster immune globulin) if the mother got varicella between 5 days before and 2 days after delivery. Babies who get varicella in the first 2 weeks of life should get IV acyclovir. (Page 957, Compendium 2014).

PARVOVIRUS B19, the virus causing FIFTH'S DISEASE

Parvovirus B19 is the virus that causes Fifth’s disease. Fifth’s disease is a common childhood illness, and outbreaks occur commonly in nursery schools and day care centers. It is usually a benign and self limited disease in children, presenting with high fevers and a rash on the face that has a red “slapped cheek” appearance, and a body rash as well.

A person is infectious about 5-10 days after they are exposed, which is before the rash and symptoms, and they are no longer infectious once the rash is present. It is transmitted by hand to mouth contact and respiratory droplets. Pregnant women who contract parvovirus can infect the fetus, with the most significant effects occurring under 20 weeks of pregnancy.

Parvovirus is not associated with birth defects, but it can lead to miscarriage, fetal anemia that can cause death or require in utero fetal transfusion, or it can lead to stillborn. Pregnant women who contract parvovirus should have a sonogram weekly for 10 weeks to make sure that the baby is not getting anemic, and if it does, it may require in utero transfusions.

There is no vaccine to prevent parvovirus, and no known treatment except supportive care of the mother. If there is an outbreak of parvovirus, the pregnant patient can have titers done to see if she is immune to parvovirus. If she is there is nothing to do, and she cannot catch it again and there is no risk to the fetus. If the pregnant woman has no immunity to parvovirus she should attempt to avoid contact with and exposure to infected populations.


Yeast infections are very common in women but particularly in pregnancy due to the compromised immune system.

Yeast grows in warm, moist places, and staying dry and cool and avoiding tight clothes and synthetic materials may help.

Prevention of yeast infections involves wearing loose, cotton clothes that are not tight and are breathable. Avoidance of thong underwear, wiping front to back and practicing good hygiene is also important. Antifungals are the mainstay of treatment for yeast infections, with over the counter monistat being the most commonly used medication internally, and for external use, mycolog ointment (a combination of an antifungal and a steroid) works well and is safe in pregnancy.

Yeast cannot harm the developing fetus and does not cause any birth defects or any problems. Treatment of yeast is to relieve maternal discomfort.


Urinary tract infections are very common in women and easily treated with a variety of antibiotics.


Symptoms usually include burning with urination, frequency, urgency and occasionally grossly bloody urine.

In pregnancy, a condition called asymptomatic bacteruria may be present. The patient may not experience any symptoms at all, but can be harboring a significant amount of bacteria in the urine, which will only be found if a clean catch urine is obtained and a culture is done. This clean catch urine is done after wiping front to back with an antiseptic wipe 3 separate times, losing the first part of the urine stream in the toilet, and capturing the later part of the urine in the sterile cup.

Even if the patient doesn’t have symptoms, if the culture shows an infection, the patient should be treated with an antibiotic. If left untreated, asymptomatic bacteruria in pregnancy can lead to a kidney infection 30% of the time. Treating a symptomatic or asymptomatic UTI in the pregnant woman is different than treating the non pregnant woman.

Certain antibiotics are safe, while others are not.


The mainstay of treatment for UTIs in pregnancy are penicillins (ampicillin or amoxicillin) or cephalosporins (keflex) or macrobid. Antibiotics that are commonly used in non pregnant women that cannot be used in pregnant women include ciprofloxacin and levaquin.

Prevention of UTIs in pregnancy include not holding in the urine too long, voiding right after intercourse, wiping front to back, and in patients who have a history of recurrent UTIs, a daily preventative tablet of cranberry/vitamin C is used to acidify the urine which can prevent adherence of bacteria to the bladder wall.

Documented recurrent UTIs in pregnancy may require the use of suppression with antibiotics given nightly for the remainder of the pregnancy.

Untreated UTIs can lead to an ascending kidney infection called pyelonephritis. This can present with fever, chills, and back pain, and can lead to bacteria going into the bloodstream of the patient which can cause sepsis (an overwhelming whole body infection that travels through the bloodstream and which can affect many organ systems). This can lead to preterm labor and delivery and even maternal and or fetal death.

Pregnant patients with pyelonephritis should be admitted to the hospital and treated with intravenous antibiotics that are broader in spectrum than those used for the average urinary tract infection.


Listeria is a bacteria that is commonly identified in certain groups of food products, and is usually a more benign condition in non pregnant, immumocompetent patients.

In those patients who are pregnant, contracting Listeria can be dangerous or even deadly for mother or baby. Pregnant women present most commonly with flu like symptoms, fever, body aches, chills and back pain. Preterm labor may also be present.

The most common culprit for Listeria is soft unpasteurized cheeses such as feta, brie, cammembert, goat, Mexican queso blanco or gorgonzola cheese. Any of these cheeses that are pasteurized (where you actually see it on the label) are fine to have. Listeria can also be the result of drinking raw milk or eating contaminated or spoiled food. Listeria has also been found in hot dogs and deli meats.

Prevention includes avoiding raw milk and unpasteurized cheese, washing vegetables thoroughly before eating, keeping the refrigerator at 40F or lower and the freezer at OF or lower, washing hands, knives and cutting boards after they come into contact with raw food, cooking meats well (ground beef 160F, chicken 170F and turkey 180F internal temperatures). Hot dogs and lunch meats should only be eaten if reheated steaming hot (don’t use microwave for this because heating can be uneven), don’t eat prepackaged salads containing ham, chicken, egg, tuna or seafood, and don’t eat refrigerated smoked seafood. (up to date, LIsteria monocyogenes infection, Author Michael S. Gelfand, last updated July 9, 2013).

Diagnosis of Listeria in a patient with fever and flu like symptoms in pregnancy involves blood cultures that are positive for Listeria, and treatment involves IV penicillin and supportive care. Concern arises for pregnant women developing sepsis and even death from this disease and the baby is also at risk for severe sequelae, sepsis and death. Prompt care for any pregnant woman who develops a high fever and flu like symptoms is essential, as early diagnosis and treatment improves outcomes.


Group B strep is a bacteria that commonly colonizes the genital tract of pregnant women. About 30% of women carry group B strep. Untreated, this bacteria has the potential of infecting the fetus and causing pneumonia or meningitis and can lead to neonatal death.

Prevention involves culturing the vaginal/ anal area of the pregnant woman at 35-37 weeks gestation, and treating in active labor or with ruptured membranes. Women who have preterm premature rupture of the membranes less than 37 weeks, those who have fever in labor, those patients who have had a group B strep UTI in pregnancy and those who have had a prior baby with group B strep disease should be treated in labor regardless of culture.


The treatment of choice is penicillin, and for those patients who are allergic to penicillin, alternatives include clindamycin or vancomycin and the lab that does the culture will check to see if the bacteria is sensitive to these antibiotics. It is optimum for the mother to receive 2 doses of antibiotics 4 hours apart prior to delivery for maximal protection. If this does not occur, the nursery will observe the baby for signs and symptoms of infection. If any signs of infection in the baby are identified, antibiotics are promptly administered.


There are two types of herpes simplex virus- I and II. With oral herpes (oral cold sores) 80% are due to HSV 1 and 20% are due to HSV 2. With genital herpes, 80% is due to HSV type 2 and 20% is due to HSV type 1.

Oral herpes infection is extremely common with up to 60% of people being infected, while genital herpes infections can approach 30% in the population. Prevention of genital herpes is not perfect and cannot be guaranteed, but includes condom use, and not having sex with prodromal symptoms (tingling or burning prior to outbreak) or herpes infection until all of the lesions are totally gone. In patients who have genital herpes, taking suppression with valtrex on a daily basis can decrease viral shedding and transmission.

In pregnancy, patients who have a prior history of genital herpes but have no lesions or prodromal symptoms are at low risk of transmitting disease to their fetus, but are given daily suppression with valtrex from 36 to 40 weeks. This decreases the chances that the patient will have an outbreak around the time of delivery. These patients are permitted to deliver vaginally. If a patient has any signs or prodromal symptoms or evidence of an outbreak around the time of delivery, it is contraindicated for that patient to deliver vaginally, and a c-section should be performed as soon as labor ensues or if membranes rupture.

Primary genital herpes is a much more dangerous situation in pregnancy than recurrent herpes, especially if primary infection occurs late in the pregnancy, around the time of delivery. Primary genital herpes can present as an outbreak 3-21 days after exposure and can result in fever, swollen lymph nodes in the groins, blisters on the genital area, flu like symptoms, and difficulty urinating.

In the first trimester of pregnancy the virus can be transmitted through the maternal bloodstream via the placenta to the fetus and can cause serious birth defects. If it is contracted closer to term, the fetus can develop severe effects as well, and this can lead to neonatal encephalitis (brain infection) leading to brain damage and death.

Women who have never had genital herpes whose partner has a history of it should consider refraining from intercourse during the pregnancy to avoid contracting a primary infection in pregnancy. In pregnant patients who receive oral sex from a partner with oral herpes there is a risk of contracting genital herpes from an oral lesion.


Infections can be acquired at any age and stage of life.

Pregnancy is a particularly precarious time to catch an infection due to the relative state of immuno-compromise with a heightened risk of more serious and severe infection in the mother, with its resultant sequelae. In addition, the risk of transmission of the infection to the fetus or neonate adds an exponential element of risk and danger. Some infections can be transmitted through the placenta to the fetus, causing birth defects that can lead to lifelong disability or death.

Other infections can infect the neonate directly and cause equally devastating consequences. Prevention is always better than cure, and knowledge about the ways to prevent infections in pregnancy that can have untoward maternal and fetal outcomes can allow us to do our best in preventing the infection before it is contracted.

Some infections are amenable to vaccination before or during pregnancy, while others are preventable by restricting or eliminating foods or practices. If prevention is not possible and a pregnant woman contracts one of these virulent infections, it is important to know about what symptoms may be present and what to look out for, so that medical attention can be speedily obtained, potentially reducing the effects for mother and fetus, or allowing for treatment options in utero or after delivery.


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