Why Early Pregnancy Feels Like the Flu (and How to Tell the Difference From Actual Illness)

Reviewed by FormBlends Medical Team · Last updated September 5, 2026 · Sources listed below

Key Takeaways

• Progesterone elevation in early pregnancy causes fatigue, low-grade temperature increases, nasal congestion, and body aches that closely mimic viral illness
• Fatigue, nasal congestion, mild aches and a sense of warmth are common in weeks 4 to 8; an earlier version of this page attached a 60 percent figure to them, and that number had no source
• Real influenza during pregnancy is more likely to cause illness that results in hospitalization (CDC, reviewed September 2024); in one large study the odds rose across pregnancy from 1.4 times in weeks 14 to 20 to 4.7 times in weeks 37 to 42 (Neuzil et al., 1998)
• Fever above 100.4°F (38°C) is NOT a normal pregnancy symptom and requires same-day medical evaluation

The short answer

Early pregnancy triggers progesterone surges that raise basal body temperature, suppress immune signaling, increase nasal blood flow, and cause widespread inflammation. The combination produces fatigue, congestion, mild body aches, and low-grade warmth that feel identical to early viral illness. Most symptoms peak at 6 to 8 weeks and improve by week 12 as the body adapts.

Table of contents

1. The hormone-immune mechanism: why pregnancy mimics infection
2. What most articles get wrong about "pregnancy flu"
3. Symptom-by-symptom breakdown: pregnancy vs actual flu
4. The decision tree: when flu-like symptoms mean real illness
5. Medications safe and unsafe during early pregnancy
6. The GLP-1 complication: pregnancy symptoms on weight-loss medications
7. When to call your provider (same-day vs emergency criteria)
8. The immune suppression question: are you actually more vulnerable?
9. Corrections and updates, September 2026
10. Acetaminophen in pregnancy: what changed in September 2025
11. What the GLP-1 labels say about pregnancy
12. FAQ
13. Sources

The hormone-immune mechanism: why pregnancy mimics infection

The "flu-like" sensation in early pregnancy comes from three overlapping physiological changes, all driven by the same hormone cascade that maintains the pregnancy.

1. Progesterone-induced temperature elevation.

Progesterone rises steeply through the first trimester as the corpus luteum and then the placenta produce it. Correction, September 2026: an earlier version printed specific ng/mL ranges attributed to Csapo et al. (1973); those papers studied progesterone replacement after removal of the corpus luteum and are not a reference-range source, so the numbers have been removed. Progesterone acts on the hypothalamic thermoregulatory center, raising basal body temperature by roughly 0.5 to 1.0°F above the pre-pregnancy baseline.

This is the same mechanism fertility tracking relies on: the temperature shift after ovulation confirms progesterone production. In pregnancy, the shift persists instead of dropping before menstruation. The sustained elevation feels like low-grade fever, especially in the evening when core temperature naturally peaks.

The key distinction: progesterone-induced warmth stays below 100.4°F (38°C). Anything higher suggests infection, not hormonal change.

2. Immune system recalibration.

Pregnancy requires partial immune suppression to prevent rejection of the fetus, which is genetically half foreign tissue. The shift happens through changes in T-helper cell balance, specifically a Th1-to-Th2 shift (Wegmann et al., Immunology Today 1993).

Th1 cells produce pro-inflammatory cytokines (IL-2, IFN-gamma, TNF-alpha) that fight intracellular pathogens but also attack foreign tissue. Th2 cells produce anti-inflammatory cytokines (IL-4, IL-10) that tolerate foreign antigens but are less effective against viruses.

The Th2 shift is protective for the pregnancy but creates a cytokine profile similar to early viral infection: elevated IL-6, increased acute-phase proteins, generalized inflammation. The body interprets this as mild systemic illness, triggering fatigue, malaise, and muscle aches.

Correction, September 2026: an earlier version cited a 2011 Journal of Reproductive Immunology study (Kraus et al.) reporting IL-6 levels 40 percent higher at 6 weeks and a correlation with fatigue. The Kraus VIP study is in the Journal of Clinical Immunology (2012) and reports neither figure. The mechanism above rests on Wegmann et al. (1993) for the Th1-to-Th2 shift; we no longer attach a percentage to it.

3. Vascular and mucous membrane changes.

Estrogen rises in parallel with progesterone, increasing blood volume by 40 to 50% across pregnancy (Bernstein et al., Obstetrics & Gynecology 2001). The expansion starts in the first trimester, causing:

• Nasal mucosa engorgement (pregnancy rhinitis), producing congestion identical to viral upper respiratory infection
• Increased capillary permeability, causing mild tissue swelling
• Sinus pressure from increased blood flow to facial vasculature

About 22 percent of pregnant women develop pregnancy rhinitis, the cumulative incidence in a study of 599 women (Ellegård et al., Gynecologic and Obstetric Investigation 2000). It feels like a head cold but produces clear discharge, not the yellow or green mucus typical of bacterial infection.

What most articles get wrong about "pregnancy flu"

The term "pregnancy flu" appears across patient education websites, but it's medically imprecise in a way that causes real harm. The error: conflating normal pregnancy symptoms with actual influenza risk.

The misconception: "Pregnancy flu is a harmless early pregnancy symptom that goes away on its own."

Why it's dangerous: Actual influenza during pregnancy is a medical emergency. The CDC says flu during pregnancy is more likely to cause illness that results in hospitalization (CDC, reviewed September 17, 2024). The best-known estimate comes from Neuzil et al. (American Journal of Epidemiology 1998): compared with postpartum women, the odds of a cardiopulmonary hospitalization during flu season rose from 1.44 at 14 to 20 weeks to 4.67 at 37 to 42 weeks. The risk is highest late in pregnancy but present throughout. Correction, September 2026: an earlier version attributed a flat fourfold figure to Rasmussen et al. (2012); the citation was wrong and has been replaced.

The 2009 H1N1 pandemic data is stark: pregnant women accounted for 5 percent of reported deaths from April to August 2009 (30 deaths), and 22.6 percent of hospitalized pregnant patients were admitted to intensive care (Siston et al., JAMA 2010). Correction, September 2026: an earlier version added population-share and per-100,000 mortality figures that are not in that paper; they have been removed.

The physiological reason: the Th2 immune shift that prevents fetal rejection also impairs antiviral defense. Pregnant women clear influenza virus more slowly, develop higher viral loads, and progress to pneumonia faster than non-pregnant adults.

The correction: Flu-like symptoms from hormonal changes are normal. Actual influenza is a serious threat. The distinction matters, and the decision tree below provides the criteria to tell them apart.

The second error in popular content: overstating the "pregnancy glow" narrative while understating how miserable early pregnancy can feel. Correction, September 2026: an earlier version cited a 2016 BMC Pregnancy and Childbirth meta-analysis (Lacasse et al.) with 70 and 40 percent fatigue figures. No such meta-analysis exists; Lacasse et al. published a 2008 BJOG study on nausea and quality of life. The figures have been removed.

Normalizing the experience is important. Telling women they should feel "glowing" when they actually feel like they have mono creates unnecessary anxiety.

Symptom-by-symptom breakdown: pregnancy vs actual flu

Symptom	Early pregnancy pattern	Influenza pattern	Key distinguishing feature
Fatigue	Gradual onset over 1-2 weeks, constant, improves with rest but returns quickly	Sudden onset, severe, accompanied by weakness that prevents normal activity	Flu fatigue is incapacitating; pregnancy fatigue is profound but functional
Body temperature	Basal temp elevated 0.5-1.0°F, feels warm but not feverish, no chills	Fever 100.4°F+, often 102-104°F, with rigors and chills	Actual fever (100.4°F+) is NOT a pregnancy symptom
Body aches	Mild, diffuse, worse in lower back and pelvis, improves with position change	Severe myalgia, especially legs and back, does not improve with rest	Flu aches are described as "bones hurting"
Nasal congestion	Clear discharge, worse at night, no facial pain, lasts weeks to months	Yellow/green discharge after 2-3 days, facial pressure, resolves in 7-10 days	Pregnancy rhinitis produces clear mucus only
Headache	Mild, frontal, related to hydration and blood sugar, improves with eating	Severe, retro-orbital, photophobia, does not improve with food	Flu headache is often described as "worst headache of my life"
Nausea	Gradual onset, worse with empty stomach, improves with small frequent meals, lasts weeks	Sudden onset, often with vomiting, improves in 24-48 hours	Pregnancy nausea is food-triggered; flu nausea is constant
Onset pattern	Symptoms build over 5-10 days	Symptoms appear within 6-12 hours	Sudden onset strongly suggests infection
Duration	Weeks to months (typically peaks week 6-8, improves week 12+)	5-7 days for acute phase	Symptoms lasting >2 weeks without improvement suggest pregnancy, not flu

The single most reliable distinguishing feature: fever. Progesterone raises basal body temperature but never above 100.4°F. If you measure 100.4°F or higher on an oral thermometer, you have an infection, not pregnancy symptoms.

The decision tree: when flu-like symptoms mean real illness

Use this framework to decide whether your symptoms require medical evaluation.

START: You have flu-like symptoms and suspect early pregnancy.

Question 1: Do you have measured fever ≥100.4°F (38°C)?

• YES → Call your provider same day. Fever is not a normal pregnancy symptom.
• NO → Continue to Question 2.

Question 2: Did symptoms start suddenly (over 6-12 hours)?

• YES → High suspicion for viral illness. Continue to Question 3.
• NO (gradual onset over days to weeks) → More consistent with pregnancy. Continue to Question 4.

Question 3: Do you have respiratory symptoms (cough, shortness of breath, chest pain)?

• YES → Call your provider same day. Influenza or other respiratory infection likely.
• NO → Continue to Question 4.

Question 4: Can you perform normal daily activities despite fatigue?

• NO (bedbound, unable to work, severe weakness) → Call your provider within 24 hours.
• YES (tired but functional) → Consistent with early pregnancy. Continue to Question 5.

Question 5: Have symptoms been stable or worsening for >14 days?

• WORSENING → Call your provider within 48 hours.
• STABLE or IMPROVING → Consistent with normal early pregnancy. Monitor at home with the following red flags.

RED FLAGS requiring same-day contact:

• Fever ≥100.4°F at any point
• Vomiting more than 3 times in 24 hours
• Unable to keep down liquids for >12 hours
• Severe headache with vision changes
• Severe abdominal pain
• Vaginal bleeding
• Dizziness or fainting

RED FLAGS requiring emergency care:

• Difficulty breathing or shortness of breath at rest
• Chest pain
• Confusion or altered mental status
• Severe dehydration (no urination for >12 hours, dark urine, dry mouth)
• Coughing up blood

Medications safe and unsafe during early pregnancy

Most women reach for over-the-counter medications when they feel flu-like symptoms. The safety profile changes dramatically in pregnancy.

SAFE for symptom management in early pregnancy:

• Acetaminophen (Tylenol): for body aches or mild temperature elevation, at the lowest effective dose and within the package maximum. It remains the analgesic generally regarded as appropriate throughout pregnancy. On September 22, 2025 the FDA and HHS announced a label change concerning acetaminophen use in pregnancy; the same day ACOG stated that not a single reputable study has concluded that acetaminophen use in any trimester causes neurodevelopmental disorders, and the American Academy of Pediatrics reaffirmed its position on September 30, 2025 (as summarized by the University of Illinois Chicago Drug Information Group, November 2025). Discuss dose and duration with your provider.
• Vitamin B6 (pyridoxine): 25 mg three times daily for nausea. Well-studied for pregnancy nausea with strong safety data (Matthews et al., Cochrane Database of Systematic Reviews 2015).
• Doxylamine (Unisom SleepTabs): 12.5 mg at bedtime for nausea and sleep. Often combined with B6 (Matthews et al., Cochrane 2015).
• Saline nasal spray: Unlimited use for congestion. No systemic absorption.
• Humidifier: For nasal congestion and dry airways.

UNSAFE or use with caution:

• Ibuprofen (Advil, Motrin): Avoid in the first trimester; a Danish registry study found NSAID prescriptions associated with higher miscarriage risk (Nielsen et al., BMJ 2001). Use only if acetaminophen fails and under provider guidance, and ask about NSAID restrictions later in pregnancy.
• Aspirin: Avoid in first trimester except low-dose (81 mg) for specific medical indications.
• Naproxen (Aleve): Same concerns as ibuprofen. Avoid.
• Decongestants (pseudoephedrine, phenylephrine): Avoid in the first trimester unless your provider advises otherwise; pseudoephedrine is among the most commonly used over-the-counter drugs in pregnancy (Werler et al., American Journal of Obstetrics and Gynecology 2005), and concern about a small increase in some birth defects has been raised in the literature. Second and third trimester use is controversial.
• DayQuil, NyQuil, Theraflu: Contain multiple ingredients including decongestants and sometimes alcohol. Avoid.
• Cough suppressants with codeine: Avoid unless prescribed.

The influenza vaccine:

• SAFE and RECOMMENDED at any point in pregnancy.
• Inactivated vaccine only (not live attenuated nasal spray).
• Reduced the risk of flu-associated hospitalization in pregnancy by about 40 percent in a 2010 to 2016 multi-site study (Thompson et al., Clinical Infectious Diseases 2019), and the CDC cites a 2013 study finding vaccination cut the risk of flu by up to one-half (CDC, reviewed September 17, 2024).
• If you have flu-like symptoms and are unvaccinated, ask your provider about the vaccine once illness resolves.

Antiviral medications (oseltamivir/Tamiflu):

• Recommended by the CDC for pregnant people with confirmed or suspected influenza; prompt treatment matters.
• Most effective when started within 48 hours of symptom onset.
• Reduces duration of illness and risk of complications.
• Do not wait for test results if clinical suspicion is high. Call your provider immediately if you suspect flu.

The GLP-1 complication: pregnancy symptoms on weight-loss medications

This intersection is increasingly common as GLP-1 receptor agonist use expands. If you're taking semaglutide or tirzepatide (compounded or brand-name) and develop flu-like symptoms, you face a three-way diagnostic problem: pregnancy, medication side effects, or actual illness.

The overlap:

GLP-1 medications cause nausea, fatigue, and sometimes low-grade headache, especially during titration. Early pregnancy causes the same symptoms. Both can occur simultaneously.

The critical rule: the Wegovy label (June 2026) and the Zepbound label (September 2026) both say the drug may cause fetal harm based on animal studies and instruct patients to discontinue when pregnancy is recognized. Pregnancy is not listed under Contraindications, and FDA pregnancy letter categories were retired on June 30, 2015, so "Category C" no longer applies. If you suspect pregnancy:

1. Stop the GLP-1 medication immediately.
2. Take a home pregnancy test (accurate 10-14 days after conception, which is around the time of missed period).
3. Contact your provider same day for confirmation and guidance.

Why this matters: The medication half-life is long (semaglutide about 1 week; tirzepatide about 5 days, per the labels). Stopping at the first suspicion of pregnancy minimizes fetal exposure. Both labels summarize animal reproduction studies showing potential fetal risk; the Wegovy label adds that available human data are insufficient to establish a drug-associated risk. Correction, September 2026: an earlier version cited Knudsen et al. (Reproductive Toxicology 2010), which could not be found in PubMed; it has been removed.

A practical rule: if you are on a GLP-1 medication and develop new or worsening nausea after weeks of tolerance, take a pregnancy test, because both labels say to stop the drug when pregnancy is recognized. Correction, September 2026: an earlier version claimed pregnancy nausea and GLP-1 nausea follow opposite meal patterns; that heuristic had no source and has been removed.

For detailed guidance on GLP-1 side effect patterns, see our article on managing nausea on compounded semaglutide.

When to call your provider (same-day vs emergency criteria)

The threshold for medical contact is lower in pregnancy than outside pregnancy because of the influenza risk and the medication safety questions.

Call within 2-4 hours (same day, urgent):

• Measured fever ≥100.4°F (38°C)
• Sudden onset of severe symptoms over 6-12 hours
• Cough producing colored sputum
• Shortness of breath with exertion
• Inability to keep down liquids for >12 hours
• Severe headache that doesn't respond to acetaminophen
• Abdominal pain beyond mild cramping
• Any vaginal bleeding
• Exposure to confirmed influenza case

Go to emergency department immediately:

• Difficulty breathing at rest
• Chest pain or pressure
• Severe dizziness or fainting
• Confusion or difficulty staying awake
• Severe persistent vomiting (>6 episodes in 6 hours)
• No urination for >12 hours with dark urine
• Coughing up blood
• Severe abdominal pain
• Heavy vaginal bleeding

Routine prenatal visit (schedule within 1 week):

• Mild fatigue and body aches, gradual onset, no fever
• Nasal congestion with clear discharge
• Mild nausea improving with small meals
• Symptoms consistent with early pregnancy, no red flags

The conservative approach: if you're uncertain whether symptoms are pregnancy or illness, call. The risk of untreated influenza outweighs the inconvenience of a phone consultation or office visit.

The immune suppression question: are you actually more vulnerable?

The short answer: yes, but selectively.

The Th2 immune shift impairs defense against intracellular pathogens (viruses, some bacteria) but preserves or enhances defense against extracellular bacteria and parasites. The clinical result: pregnant women are more vulnerable to severe influenza, varicella (chickenpox), and COVID-19, but not more vulnerable to common cold viruses or most bacterial infections.

The data on specific infections:

Infection	Increased severity in pregnancy?	Mechanism
Influenza	Yes (odds of hospitalization rise through pregnancy, to 4.7 times in late pregnancy; Neuzil 1998)	Impaired viral clearance, reduced lung capacity in later pregnancy
COVID-19	Yes (ICU admission about 3 times as likely; Zambrano et al., MMWR 2020)	Similar mechanism to influenza
Varicella (chickenpox)	Yes (higher risk of varicella pneumonia; no reliable percentage cited)	Impaired cell-mediated immunity
Common cold (rhinovirus)	No	Preserved mucosal immunity
Strep throat	No	Preserved antibody response
Urinary tract infection	Yes (higher progression to pyelonephritis)	Anatomical changes, not immune
Listeria	Yes (about 10 times more likely; CDC Vital Signs, June 2013)	Impaired intracellular pathogen defense

The practical implication: the flu-like symptoms you're experiencing are probably hormonal, but if they're actually influenza, the stakes are higher than they would be outside pregnancy. The decision tree above is designed around that asymmetric risk.

Prevention strategies:

• Influenza vaccine (inactivated) as soon as pregnancy is confirmed, regardless of trimester
• COVID-19 vaccination per current CDC guidance
• Avoid close contact with anyone who has confirmed respiratory illness
• Hand hygiene (the 20-second rule actually works)
• Avoid crowded indoor spaces during peak respiratory virus season (November through March in Northern Hemisphere)

For women on Wegovy who are planning pregnancy, the label says to discontinue at least 2 months before a planned pregnancy because of semaglutide's long half-life (section 8.3); the Zepbound label says to discontinue when pregnancy is recognized. Ask your prescriber about timing, then receive flu and COVID vaccines before conception if planning pregnancy during respiratory virus season.

Corrections and updates, September 2026

As of September 5, 2026, this page has been re-checked against its sources. The FDA pregnancy letter categories (A, B, C, D and X) that an earlier version used for acetaminophen, doxylamine, ibuprofen, codeine, oseltamivir and GLP-1 drugs were retired by the FDA's Pregnancy and Lactation Labeling Rule effective June 30, 2015, and have been removed; current labels describe risk in narrative form instead. Several statistics could not be traced to the studies they were attributed to and have been removed or corrected: a 60 percent prevalence of flu-like symptoms, a 40 percent IL-6 increase (Kraus), a 70 percent fatigue figure (Lacasse), a 30 percent rhinitis figure (now 22 percent, Ellegård 2000), a flat fourfold influenza hospitalization risk (now the Neuzil 1998 gradient), per-100,000 H1N1 mortality rates (Siston 2010 reports only the 5 percent share of deaths), vaccine figures attributed to Omer 2011 (now Thompson 2019 and CDC), a 20-fold Listeria risk (CDC says about 10 times), a 20 percent afebrile-flu figure, and an animal-study citation (Knudsen 2010) that could not be found. Journal names for Nielsen 2001 (BMJ) and Werler 2005 (American Journal of Obstetrics and Gynecology) were corrected. First-person claims about patterns seen in FormBlends consultations were removed.

Acetaminophen in pregnancy: what changed in September 2025

On September 22, 2025 the FDA and the Department of Health and Human Services announced a label change for acetaminophen concerning use during pregnancy. The response from professional bodies was immediate and consistent. The American College of Obstetricians and Gynecologists said the same day that not a single reputable study has successfully concluded that acetaminophen use in any trimester of pregnancy causes neurodevelopmental disorders; the World Health Organization commented on September 24, 2025; and the American Academy of Pediatrics reaffirmed its guidance on September 30, 2025 (all as summarized by the University of Illinois Chicago Drug Information Group, November 2025). For a pregnant patient with aches or a mild temperature elevation, the practical guidance is unchanged: acetaminophen at the lowest effective dose for the shortest time, within the package maximum, and a call to your provider for any measured fever of 100.4°F or higher, which MedlinePlus (reviewed August 18, 2025) also flags as the threshold for possible flu.

What the GLP-1 labels say about pregnancy

Question	Wegovy (semaglutide), label revised June 2026	Zepbound (tirzepatide), label revised August 2026
Is pregnancy a contraindication?	No; section 4 lists only medullary thyroid carcinoma or MEN 2 history and hypersensitivity	No; same two categories
What does the label say about fetal risk?	May cause fetal harm based on animal studies; human data insufficient to establish a drug-associated risk (8.1)	May cause fetal harm based on animal studies (8.1)
What to do if pregnant	Discontinue when pregnancy is recognized for weight or cardiovascular indications (8.1)	Discontinue when pregnancy is recognized (8.1)
Planning pregnancy	Discontinue at least 2 months before a planned pregnancy because of the long half-life (8.3)	No specific lead time stated
Half-life	About 1 week (12.3)	About 5 days (12.3)
Contraception note	None	Oral hormonal contraceptives may be less effective; use a non-oral or barrier method for 4 weeks after starting and after each dose escalation (7.2, 8.3)

Compounded semaglutide and tirzepatide carry no label of their own; the approved labels are the only published guidance and should be treated as the minimum.

FAQ

Are flu-like symptoms a sign of early pregnancy?

Yes, commonly. Progesterone elevation causes fatigue, mild body aches, low-grade warmth, and nasal congestion that feel similar to early viral illness. Symptoms typically start around week 5 to 6 and improve by week 12.

Can early pregnancy feel like the flu?

It can feel similar, but true influenza has distinct features: sudden onset (over hours, not days), high fever (100.4°F or higher), severe body aches, and respiratory symptoms like cough. Pregnancy symptoms build gradually and don't include actual fever.

What week of pregnancy do flu-like symptoms start?

Most women notice symptoms starting around week 5 to 6 (1 to 2 weeks after missed period), peaking at week 6 to 8, and improving by week 12. The timeline follows the progesterone curve.

Is feeling warm a sign of early pregnancy?

Yes. Progesterone raises basal body temperature by 0.5 to 1.0°F. You may feel warm, especially in the evening, but your measured temperature should stay below 100.4°F. Anything higher suggests infection.

Can you get a fever in early pregnancy?

No. Fever (100.4°F or higher) is NOT a normal pregnancy symptom. It indicates infection and requires same-day medical evaluation. Progesterone raises temperature but not to fever levels.

How long do flu-like symptoms last in early pregnancy?

For most women, symptoms peak at 6 to 8 weeks and improve significantly by 12 to 14 weeks. Some fatigue and congestion may persist into the second trimester, but the severe "flu-like" feeling typically resolves by the end of the first trimester.

Can you take Tylenol for body aches in early pregnancy?

Yes. Acetaminophen (Tylenol) remains the analgesic generally regarded as appropriate throughout pregnancy for body aches, headache or mild temperature elevation; ACOG restated this on September 22, 2025 after the FDA and HHS announced a label change. Use the lowest effective dose within the package maximum, for the shortest time. Avoid ibuprofen and aspirin in the first trimester unless prescribed.

Should I get a flu shot if I have flu-like pregnancy symptoms?

Yes, once you confirm the symptoms are from pregnancy and not active infection. The inactivated influenza vaccine is safe and recommended at any point in pregnancy. The CDC cites studies showing it cut the risk of flu by up to one-half and reduced flu hospitalization in pregnancy by about 40 percent, and it also helps protect the newborn in the first months of life.

Can pregnancy cause sinus congestion?

Yes. About 22 percent of pregnant women develop pregnancy rhinitis from increased blood flow to nasal mucosa (Ellegård et al., 2000). It produces clear nasal discharge, congestion worse at night, and can last throughout pregnancy. It's annoying but harmless. Saline spray and humidifiers help.

What's the difference between pregnancy fatigue and flu fatigue?

Pregnancy fatigue builds gradually over days to weeks, is profound but allows you to function, and improves with rest. Flu fatigue hits suddenly, is incapacitating (you can't get out of bed), and doesn't improve much with rest. If you were fine yesterday and can't function today, suspect flu.

Can I have the flu without a fever during pregnancy?

Yes, but it's less common, and some flu cases do occur without fever. Other features (sudden onset, severe body aches, cough, known exposure) help identify flu even without fever. When in doubt, call your provider.

Is it normal to feel sick all day in early pregnancy?

Yes. Despite the term "morning sickness," nausea and malaise can occur any time of day. Most pregnant women experience some nausea, and for many it occurs throughout the day, not just in the morning. The pattern is worse on empty stomach, better with small frequent meals.

Can GLP-1 medications cause pregnancy-like symptoms?

Yes. Semaglutide and tirzepatide cause nausea and fatigue, especially during dose escalation. There is no reliable way to tell them apart by timing. If you're on a GLP-1 medication and develop new symptoms, take a pregnancy test; both the Wegovy and Zepbound labels say to stop the drug when pregnancy is recognized because of potential fetal harm.

When should I go to the ER for flu-like symptoms during pregnancy?

Go immediately if you have difficulty breathing, chest pain, confusion, severe persistent vomiting, no urination for more than 12 hours, or coughing up blood. These suggest serious complications requiring emergency care.

Can early pregnancy cause chills without fever?

Mild chills can occur during rapid hormone fluctuations, but they're uncommon and should be brief. Chills with rigors (shaking) suggest infection even if you haven't measured a fever yet. Take your temperature and call your provider if chills persist.

Are FDA pregnancy categories like Category B or C still used?

No. The FDA's Pregnancy and Lactation Labeling Rule removed the letter categories A, B, C, D and X from prescription drug labels effective June 30, 2015, replacing them with narrative summaries of risk, data and clinical considerations. Older articles, including an earlier version of this one, still quote letters; they are not part of any current label. Ask a pharmacist or your provider what the current label says about a specific medicine.

Did the FDA say acetaminophen is unsafe in pregnancy in 2025?

On September 22, 2025 the FDA and HHS announced a label change concerning acetaminophen use in pregnancy. The same day ACOG stated that not a single reputable study has concluded that acetaminophen in any trimester causes neurodevelopmental disorders, and the American Academy of Pediatrics reaffirmed its guidance on September 30, 2025 (University of Illinois Chicago Drug Information Group, November 2025). Acetaminophen remains the analgesic generally regarded as appropriate in pregnancy at the lowest effective dose.

Is Wegovy contraindicated in pregnancy?

Not formally. The June 2026 Wegovy label lists only two contraindications, neither of them pregnancy. It does say the drug may cause fetal harm based on animal studies, that patients taking it for weight or cardiovascular risk should stop when pregnancy is recognized, and that it should be stopped at least 2 months before a planned pregnancy because of its roughly one-week half-life. The Zepbound label says to discontinue when pregnancy is recognized.

Related guides

• Flu-Like Symptoms During Early Pregnancy: The Hormonal Mechanism, the Actual Flu, and the Red Flags That Mean Something Else
• Early Pregnancy and Flu-Like Symptoms: The Hormonal Overlap, the Decision Tree, and When to Test
• Why Phentermine Feels Like It's Not Working After 1 Week (and What's Actually Happening)
• First Tirzepatide Injection: What It Feels Like
• Is Ozempic a Shot? Everything About Semaglutide Injection Delivery, Needle Size, and What the Injection Actually Feels Like
• Amide vs Peptide Bond: What Is the Actual Difference? | FormBlends

Sources

1. Wegmann TG et al. Bidirectional cytokine interactions in the maternal-fetal relationship: is successful pregnancy a TH2 phenomenon? Immunology Today. 1993.
2. Kraus TA et al. Characterizing the pregnancy immune phenotype: results of the viral immunity and pregnancy (VIP) study. Journal of Clinical Immunology. 2012.
3. Bernstein IM et al. Maternal plasma volume expansion in early pregnancy. Obstetrics & Gynecology. 2001.
4. Ellegård EK et al. Pregnancy rhinitis. Gynecologic and Obstetric Investigation. 2000.
5. Neuzil KM et al. Impact of influenza on acute cardiopulmonary hospitalizations in pregnant women. American Journal of Epidemiology. 1998.
6. Siston AM et al. Pandemic 2009 influenza A(H1N1) virus illness among pregnant women in the United States. JAMA. 2010.
7. Matthews A et al. Interventions for nausea and vomiting in early pregnancy. Cochrane Database of Systematic Reviews. 2015.
8. Nielsen GL et al. Risk of adverse birth outcome and miscarriage in pregnant users of non-steroidal anti-inflammatory drugs: population based observational study and case-control study. BMJ. 2001.
9. Werler MM et al. Use of over-the-counter medications during pregnancy. American Journal of Obstetrics and Gynecology. 2005.
10. Thompson MG et al. Influenza vaccine effectiveness in preventing influenza-associated hospitalizations during pregnancy: a multi-country retrospective test negative design study, 2010-2016. Clinical Infectious Diseases. 2019.
11. Centers for Disease Control and Prevention. Pregnant Women and Influenza (Flu). CDC Guidelines. 2024.
12. Centers for Disease Control and Prevention. Pregnant people and influenza (flu): hospitalization risk, vaccination in any trimester, antiviral treatment. Page reviewed September 17, 2024 (cdc.gov/flu/highrisk/pregnant.htm).
13. MedlinePlus (NIH). Flu and pregnancy: fever of 100.4°F or higher, medicine use. Reviewed August 18, 2025. https://medlineplus.gov/ency/article/007443.htm
14. U.S. Food and Drug Administration. Pregnancy and Lactation Labeling Rule: removal of pregnancy letter categories, effective June 30, 2015. https://www.fda.gov/media/100406/download
15. University of Illinois Chicago Drug Information Group. What do national and international health organizations say about the link between acetaminophen use and autism? (FDA/HHS September 22, 2025; ACOG; AAP September 30, 2025; WHO September 24, 2025). November 2025. https://dig.pharmacy.uic.edu/faqs/2025-2/november-2025-faqs/what-do-national-and-international-health-organizations-say-about-the-link-between-tylenol-acetaminophen-use-and-autism/
16. Neuzil KM et al. Impact of influenza on acute cardiopulmonary hospitalizations in pregnant women. American Journal of Epidemiology, 1998. PMID 9850132. https://europepmc.org/article/MED/9850132
17. Siston AM et al. Pandemic 2009 influenza A(H1N1) virus illness among pregnant women in the United States. JAMA, 2010. PMID 20407061. https://europepmc.org/article/MED/20407061
18. Thompson MG et al. Influenza vaccine effectiveness in preventing influenza-associated hospitalizations during pregnancy, 2010-2016. Clinical Infectious Diseases, 2019. PMID 30307490. https://europepmc.org/article/MED/30307490
19. Ellegård EK et al. Pregnancy rhinitis (cumulative incidence 22 percent). Gynecologic and Obstetric Investigation, 2000. PMID 10671815. https://europepmc.org/article/MED/10671815
20. Zambrano LD et al. Characteristics of symptomatic women of reproductive age with laboratory-confirmed SARS-CoV-2 infection by pregnancy status. MMWR, November 2020. PMID 33151921. https://europepmc.org/article/MED/33151921
21. Centers for Disease Control and Prevention. Vital Signs: Listeria illnesses, deaths and outbreaks (pregnant women about 10 times more likely to get Listeria infection). June 4, 2013. https://archive.cdc.gov/www_cdc_gov/media/releases/2013/p0604-listeria-poisoning.html
22. DailyMed (NIH). Wegovy (semaglutide) prescribing information: sections 4, 8.1, 8.3 and 12.3. Revised June 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b
23. DailyMed (NIH). Zepbound (tirzepatide) prescribing information: sections 4, 7.2, 8.1, 8.3 and 12.3. Published September 2, 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b

Footer disclaimers

Platform Disclaimer. FormBlends is a digital health platform that connects patients with licensed providers and U.S.-based pharmacies. We do not manufacture, prescribe, or dispense medication directly. All clinical decisions are made by independent licensed providers.

Compounded Medication Notice. Compounded semaglutide and tirzepatide are not FDA-approved. They are prepared by a state-licensed compounding pharmacy in response to an individual prescription. Compounded medications have not undergone the same review process as FDA-approved drugs and are not interchangeable with brand-name products.

Results Disclaimer. Individual results vary. Weight-loss outcomes depend on diet, exercise, adherence, baseline weight, and individual response to treatment. Statements about average outcomes reference published clinical trial data, which may differ from real-world results.

Trademark Notice. Tylenol, Advil, Motrin, Aleve, Unisom, DayQuil, NyQuil, Theraflu, and Tamiflu are registered trademarks of their respective owners. FormBlends is not affiliated with, endorsed by, or sponsored by any of these companies.