Getting sick during pregnancy is common and, in most cases, your body fights off the illness without lasting harm to you or your baby. A typical cold or mild stomach bug will generally run its course. But pregnancy does change your immune system, heart, and lungs in ways that make certain illnesses hit harder and, in some cases, pose real risks to fetal development. The key is knowing which illnesses matter, what symptoms to watch for, and how to manage things safely.
Why Pregnancy Makes You More Vulnerable
Your immune system dials down parts of its defenses during pregnancy to avoid attacking the developing baby. That trade-off means your body is slower to fight off certain infections. At the same time, your heart is pumping significantly more blood, your lungs have less room to expand as the uterus grows, and your oxygen demands are higher. These shifts make respiratory illnesses particularly dangerous.
The flu is the clearest example. CDC surveillance data from the 2022-2023 season found that nearly half of all women aged 15 to 49 hospitalized with confirmed influenza were pregnant. That’s a staggering overrepresentation, given that pregnant women make up a small fraction of that age group at any given time. Flu vaccination during pregnancy cuts the risk of getting the flu by about half and reduces the chance of flu-related hospitalization by 40%.
When Fever Is the Real Concern
For many common illnesses, the infection itself isn’t the main threat to the baby. The fever that comes with it is. A sustained temperature above 102°F (38.9°C) lasting at least 24 hours has been linked to an increased risk of miscarriage in early pregnancy, neural tube defects like spina bifida, and stillbirth later on.
Research from the CDC found that fever around the time of conception or in early pregnancy roughly doubled the risk of neural tube defects. That risk climbed even higher in women who weren’t getting enough folic acid. Women taking the recommended 400 micrograms of folic acid daily had a much smaller increase in risk compared to those with low intake, where the risk was about four times higher than normal. This is one reason prenatal vitamins with folic acid are so strongly recommended even before pregnancy begins.
Acetaminophen (Tylenol) is considered safe for bringing down a fever during pregnancy. Keeping a fever controlled is one of the most important things you can do when you’re sick.
Infections That Carry Specific Risks
Most colds and mild viral infections don’t cross the placenta or directly affect the baby. A handful of infections are different, and worth knowing about.
Listeria is a foodborne bacteria found in deli meats, unpasteurized cheeses, and sometimes pre-washed salad greens. Pregnant women are significantly more susceptible to it, and nearly 25% of pregnancy-associated listeriosis cases result in fetal loss or death of the newborn. This is why food safety guidelines during pregnancy are so specific about avoiding certain foods.
Cytomegalovirus (CMV) is a very common virus that most adults carry without knowing it. If you catch it for the first time during pregnancy, though, it can pass to the baby. About 1 in 5 babies born with congenital CMV will have birth defects or long-term health problems. Hearing loss is the most common outcome and can worsen over the first two years of life, a critical window for language development. CMV spreads through saliva and urine, so frequent handwashing, especially around young children, is one of the best preventive steps.
Foodborne illnesses in general hit harder during pregnancy. Severe vomiting and diarrhea can lead to dehydration, which carries its own set of risks.
How Dehydration Compounds the Problem
When illness causes vomiting or diarrhea, dehydration becomes a concern on its own. In pregnancy, dehydration can lower amniotic fluid levels, which cushion and protect the baby. It can also trigger Braxton-Hicks contractions, the tightening of the uterus that typically happens in the third trimester but can start earlier when you’re dehydrated.
If you can’t keep fluids down for more than 8 hours or food for more than 24 hours, that’s a point where you need medical attention. Small, frequent sips of water, electrolyte drinks, or even ice chips can help if full glasses feel impossible.
How Illness Can Trigger Preterm Labor
Serious infections, particularly those that reach the uterus, can set off a chain of inflammatory responses that mimic or trigger labor. When the body detects a pathogen, it launches an immune response that releases signaling molecules. These same molecules promote uterine contractions and can weaken the membranes surrounding the baby, potentially leading to premature rupture of membranes or preterm labor.
This doesn’t happen with a typical cold. The risk is primarily associated with more severe or systemic infections, urinary tract infections that go untreated, or infections that reach the reproductive tract. Prompt treatment of bacterial infections with pregnancy-safe antibiotics is one of the most effective ways to prevent this cascade.
Safe Medications During Pregnancy
One of the biggest frustrations of being sick while pregnant is the limited medicine cabinet. Here’s what’s generally considered safe:
- For pain or fever: Acetaminophen (Tylenol)
- For cough: Dextromethorphan (Robitussin), guaifenesin (plain Mucinex), mentholated cough drops
- For allergies or runny nose: Loratadine (Claritin) or diphenhydramine (Benadryl)
- For chest congestion: Mentholated rub (Vicks VapoRub)
Several common medications should be avoided. Ibuprofen (Advil, Motrin), naproxen (Aleve), and aspirin are all off the table. Decongestants containing pseudoephedrine are not recommended in the first trimester. Multi-symptom formulas like NyQuil and DayQuil should be avoided due to their alcohol content and certain antihistamines. Stick to single-ingredient products rather than combination formulas.
Vaccines That Protect You and the Baby
Several vaccines are specifically recommended during pregnancy because they protect both you and the newborn in the first weeks of life, before the baby can be vaccinated.
The flu shot is recommended at any point during pregnancy and during flu season. The Tdap vaccine, which protects against whooping cough, is recommended during each pregnancy between weeks 27 and 36. This timing allows your antibodies to transfer to the baby before birth. An RSV vaccine is recommended between weeks 32 and 36 during RSV season (September through January in most of the U.S.), though only the Pfizer version is approved for use in pregnancy.
Live vaccines, including MMR (measles, mumps, rubella), varicella (chickenpox), and the nasal spray version of the flu vaccine, are not safe during pregnancy.
Warning Signs That Need Immediate Attention
Most illnesses during pregnancy are manageable at home. But certain symptoms during or after an illness warrant urgent care:
- Fever of 100.4°F (38°C) or higher
- Trouble breathing or chest tightness
- Severe vomiting that prevents keeping fluids down for 8 or more hours
- Decreased baby movement or a noticeable change in your baby’s usual pattern of kicks
- Vaginal bleeding or fluid leaking
- Severe belly pain that comes on suddenly or worsens
- A headache that won’t go away, especially if accompanied by vision changes or dizziness
Some of these symptoms overlap with pregnancy complications like preeclampsia, so they’re worth taking seriously even if you think they’re just part of being sick. Trust your instincts. If something feels wrong, it’s always reasonable to call.