Throwing up in the third trimester is more common than most people expect, and it has a wide range of causes, from ordinary mechanical pressure on your stomach to rare but dangerous liver conditions. While first-trimester nausea gets most of the attention, vomiting that appears or returns late in pregnancy deserves a closer look because some of its causes require prompt medical attention. The reassuring news is that the most frequent explanations are benign, but knowing the difference between uncomfortable and alarming can matter a great deal.
The Most Common Reason Is Simpler Than You Think
By the third trimester, your uterus has grown large enough to push your stomach and intestines upward and outward. That physical crowding reduces the space your stomach has to expand after a meal, and it increases pressure on the valve between your esophagus and stomach. The result is acid reflux, which can trigger not just heartburn but outright vomiting, especially after larger meals or when you lie down soon after eating. Rising levels of progesterone make this worse. Research has shown that progressively increasing progesterone during pregnancy relaxes the lower esophageal sphincter, allowing stomach acid to travel upward and cause reflux symptoms.1PubMed. Heartburn of pregnancy That hormonal relaxation effect is present from early pregnancy, but the mechanical crowding of the third trimester turns mild heartburn into something that can actually make you vomit.
Slow gastric emptying adds to the problem. Progesterone also slows the muscular contractions that move food through your digestive tract, so food sits in your stomach longer than usual. Combined with an increasingly compressed stomach, the sensation of fullness builds quickly, and nausea follows. Many women find they can only tolerate small meals by the final weeks of pregnancy for exactly this reason.
Nausea and Vomiting That Returns After Disappearing
A frustrating pattern many women notice is that nausea faded around weeks 12 to 14, only to return with a vengeance in the late second or third trimester. This is not the same phenomenon as first-trimester morning sickness. Early pregnancy nausea is driven primarily by rapidly rising hCG and estrogen levels, and it tracks closely with the peak and plateau of those hormones. Third-trimester nausea is more often driven by the mechanical and reflux-related issues described above, or by entirely different conditions.
That said, some women experience nausea that never fully goes away. For a subset of pregnant people, the hormonal sensitivity that caused first-trimester vomiting continues throughout pregnancy as hyperemesis gravidarum. When hyperemesis persists into the third trimester, it carries associations with low birth weight and preterm delivery, as large cohort studies from Sweden, Norway, and Canada have linked it to small-for-gestational-age births and placental dysfunction disorders.2MDPI (Medical Sciences). Hyperemesis in Pregnancy: Complications and Treatment – Section: 3.3. Complications Associated with HG If you have been vomiting throughout your entire pregnancy and it has not improved, this is worth discussing with your provider rather than assuming it is normal.
Serious Conditions That Cause Third-Trimester Vomiting
Most third-trimester vomiting is unpleasant but harmless. A small number of causes, however, are medical emergencies. The challenge is that their early symptoms can look a lot like ordinary pregnancy discomfort.
Preeclampsia and HELLP Syndrome
Preeclampsia is a condition involving high blood pressure and organ damage that typically develops after 20 weeks. When it progresses to HELLP syndrome, a severe variant involving the breakdown of red blood cells, elevated liver enzymes, and low platelet counts, nausea and vomiting become prominent symptoms. About 35% of women with HELLP syndrome experience nausea and vomiting, and around 65% have pain in the upper right abdomen or just below the breastbone.3PubMed Central. A typical presentation of previable HELLP syndrome: a case report What makes this dangerous is that the vomiting can be mistaken for a stomach bug or bad reflux, especially early on. As the syndrome worsens, so do the nausea, vomiting, and risk of serious complications including seizures and stillbirth.4PubMed. The spectrum of severe preeclampsia: comparative analysis by HELLP syndrome classification
The distinguishing features to watch for are persistent headache, visual changes like seeing spots or blurred vision, sudden swelling in the face or hands, and pain under the ribs on the right side. If vomiting appears alongside any of these symptoms, seek medical attention immediately rather than waiting it out.
Acute Fatty Liver of Pregnancy
Acute fatty liver of pregnancy is rare but life-threatening. It occurs almost exclusively in the third trimester or just after delivery, and nausea and vomiting are among its earliest symptoms.5PubMed Central. Acute fatty liver of pregnancy The condition involves fat accumulating in liver cells, which impairs liver function and can quickly cascade into organ failure. In a documented case, a 24-year-old woman at 36 weeks presented to the emergency department with nausea, vomiting, and abdominal pain that had appeared only 12 hours earlier, and she was found to meet the diagnostic criteria for acute fatty liver based on abnormal blood work including elevated bilirubin, low blood sugar, and signs of kidney injury.6American Journal of Case Reports. A 24-Year-Old Woman Presenting in the Third Trimester of Pregnancy with Nausea, Vomiting, and Abdominal Pain and Diagnosed with Acute Fatty Liver of Pregnancy
The speed of onset is what makes acute fatty liver distinctive. Women often feel fine one day and severely ill the next. Warning signs beyond vomiting include yellowing of the skin or eyes, dark urine, extreme fatigue, and confusion. Because the condition can deteriorate rapidly, delivery of the baby is typically the primary treatment, and early recognition is critical.
Gastrointestinal Problems That Mimic Pregnancy Discomfort
Pregnancy does not protect you from ordinary stomach problems, and in some ways it makes you more vulnerable. Your immune system shifts during pregnancy to tolerate the fetus, and those changes also reduce your defenses against infections. Pregnant women are more susceptible to enteric pathogens, meaning food poisoning and viral gastroenteritis can hit harder than they otherwise would.7PubMed Central. Gastroenteritis In Pregnancy: Relevance and Remedy A bout of stomach flu in the third trimester is usually self-limiting, but the dehydration risk is higher because you are already working with expanded blood volume and increased fluid demands.
More concerning are surgical conditions. Appendicitis during the third trimester is notoriously difficult to diagnose because the growing uterus pushes the appendix out of its usual location, which changes where the pain shows up. Delay in diagnosing appendicitis increases the risk of complications for both mother and baby, so clinicians tend to favor an aggressive approach, operating even when the diagnosis is uncertain rather than waiting and risking a rupture.8PubMed Central. Suspicion of acute appendicitis in the third trimester of pregnancy: pros and cons of a laparoscopic procedure
Bowel obstruction is another condition that gets missed in pregnancy. Women who have had previous abdominal or pelvic surgeries can develop adhesions that trap a loop of intestine, causing severe vomiting and abdominal pain. One case report described a woman at 28 weeks with a history of prior surgery who came to the emergency room with vomiting and epigastric pain. The obstruction was initially attributed to normal pregnancy discomfort before the correct diagnosis was made.9PubMed Central. Intestinal Obstruction in the Third Trimester of Pregnancy: Maternal and Fetal Outcomes If you have had previous abdominal surgery and develop sudden-onset vomiting with cramping that comes in waves, mention your surgical history to your care team.
How Third-Trimester Vomiting Can Affect Your Baby
Mild or intermittent vomiting in the third trimester generally does not harm the baby. Your body is remarkably good at prioritizing the fetus’s nutritional supply even when you feel terrible. The concern arises when vomiting is severe, prolonged, or accompanied by poor food intake over days or weeks. A large observational study in rural Nepal found that women who experienced nausea, vomiting, and poor appetite specifically during the third trimester had a modestly higher risk of delivering a baby with low birth weight or small for gestational age compared to women without those symptoms.10PubMed Central. Nausea, vomiting and poor appetite during pregnancy and adverse birth outcomes in rural Nepal: an observational cohort study
The key variable is how much nutrition you are actually able to keep down. A few episodes of vomiting per week with otherwise adequate intake is a different situation from vomiting multiple times a day and being unable to eat. If you are losing weight in the third trimester, unable to keep fluids down for more than 12 hours, or noticing decreased fetal movement, those are reasons to get evaluated rather than wait for your next scheduled appointment.
Medications That Can Help
The first-line approach for pregnancy nausea at any stage is typically vitamin B6, often combined with the antihistamine doxylamine. This combination is available over the counter in many countries and has a long safety record. When it is not enough, your provider may discuss ondansetron, a medication originally developed for chemotherapy-related nausea that has become widely used in pregnancy. A large multinational analysis found that ondansetron use during pregnancy was not associated with increased risks of fetal death, spontaneous abortion, stillbirth, or major birth defects.11JAMA Network Open. Comparison of Pregnancy Outcomes of Patients Treated With Ondansetron vs Alternative Antiemetic Medications in a Multinational, Population-Based Cohort A separate scoping review looking specifically at the safety profile of ondansetron for pregnancy nausea concluded that it carried minimal complications for maternal health and late pregnancy outcomes, with no elevated risk of birth defects overall.12PubMed Central. A Scoping Review of 5-HT(3) Antagonist Antiemetic Medication Safety in the Management of Nausea and Vomiting of Pregnancy
The evidence on ondansetron is not perfectly clean. Some earlier studies raised questions about a small possible increase in certain cardiac or oral cleft defects, but the absolute risk changes were tiny and the study designs had limitations. In practice, most providers consider ondansetron a reasonable option when other treatments have failed, especially in the second and third trimesters when the risk window for early organ formation has passed.
Ginger, Acupressure, and Other Non-Drug Approaches
If you prefer to avoid medication or want something to use alongside it, ginger has the strongest evidence among non-pharmaceutical options. An umbrella review of systematic reviews found that ginger supplements, usually taken at doses between 450 and 1,950 milligrams daily, significantly decreased the severity and occurrence of nausea compared to placebo, with the benefit being more consistent for nausea than for vomiting. The same body of research found that ginger did not raise the risk of miscarriage or notable side effects compared to placebo or vitamin B6.13PubMed Central. Treatment of Nausea and Vomiting With Zingiber officinale in Pregnancy: An Umbrella Review of Systematic Reviews With Meta-Synthesis Ginger tea, ginger capsules, and ginger chews are all reasonable options. The main side effect some women report is heartburn, which is worth knowing about since reflux may already be an issue in the third trimester.
Acupressure on the P6 point, a spot on the inner wrist about three finger-widths above the wrist crease, is another option with some supporting evidence. A systematic review of complementary therapies for pregnancy nausea found that both ginger and P6 acupressure could be recommended with reasonable confidence, with no adverse effects reported.14PubMed Central. Effects of Complementary Medicine on Nausea and Vomiting in Pregnancy: A Systematic Review Wristbands marketed for motion sickness work on this same principle. The evidence is not as strong as it is for ginger, but the intervention is essentially risk-free.
Practical meal strategies can also make a meaningful difference in the third trimester specifically. Because the physical compression of your stomach is a major driver of nausea at this stage, eating five or six small meals instead of three large ones reduces the amount of food pressing against that relaxed esophageal valve. Staying upright for at least 30 minutes after eating helps as well. Cold foods tend to have less odor than hot ones, which can be useful if smells are triggering your nausea. Keeping plain crackers or dry toast by the bed for early morning is a standard recommendation for first-trimester nausea, but it works just as well late in pregnancy when nighttime reflux leaves you feeling queasy at dawn.
The Anxiety Connection in Late Pregnancy
The emotional landscape of the third trimester is different from early pregnancy, and that can play into physical symptoms. Research on emotional experiences across the three trimesters found that while first-trimester feelings are dominated by the physiological symptoms of nausea, vomiting, and dizziness, the third trimester is characterized more by anxiety and emotional distress.15Journal of Clinical Psychology. Emotional experiences during the three trimesters of pregnancy Anxiety about labor, the health of the baby, and the transition to parenthood peaks in the weeks before delivery, and anxiety is a well-established trigger for nausea in people who are not pregnant at all. In the context of a body that is already primed for nausea by reflux, hormones, and mechanical compression, added stress and worry can push the balance from “I feel a little off” to “I’m actually vomiting.”
This does not mean the vomiting is “all in your head.” It means the nervous system that manages your gut and the nervous system that processes worry are deeply interconnected. If your nausea worsens during stressful moments or on nights when you are lying awake catastrophizing about delivery, the anxiety component is worth addressing on its own terms. Prenatal yoga, breathing exercises, and even just talking openly with your partner or a therapist about birth fears can reduce the physiological stress response enough to take the edge off nausea.
Why Pregnancy Nausea Exists at All
It is worth stepping back to consider why pregnancy produces nausea in the first place. One leading hypothesis, supported by a broad evidence review, is that nausea and vomiting during pregnancy evolved as a protective mechanism to keep pregnant women from eating foods that could carry dangerous pathogens or plant toxins during a period of heightened vulnerability.16PubMed. Nausea and vomiting of pregnancy in an evolutionary perspective The immune system is deliberately suppressed during pregnancy to prevent the body from attacking the fetus, and that suppression leaves you more open to foodborne infections. From this perspective, nausea is a behavioral strategy: if you feel sick at the smell of meat that might be slightly off, you are less likely to eat it and get infected.
A related analysis frames pregnancy sickness as behavioral prophylaxis against infection, noting that the period of greatest nausea sensitivity aligns with the period of maximal immune vulnerability, and that dietary behavior during this time shifts dramatically through aversions and cravings.17PubMed. Reproductive immunosupression and diet. An evolutionary perspective on pregnancy sickness and meat consumption This framework applies most neatly to first-trimester nausea, when the embryo is most vulnerable to toxins and the immune shift is most dramatic. Third-trimester nausea fits less cleanly into the evolutionary story, since by that point the baby’s organs are fully formed and the main risks are different. The mechanical and hormonal explanations covered earlier are more relevant for late-pregnancy vomiting. Still, some of the heightened smell sensitivity and food aversions that started early in pregnancy can linger or resurface, and understanding them as a feature rather than a defect of the pregnant body can make the experience slightly less miserable.
When to Call Your Doctor Versus When to Ride It Out
Sorting third-trimester vomiting into “unpleasant but fine” and “needs urgent attention” comes down to a handful of red flags. Seek same-day evaluation if vomiting is accompanied by any of the following:
- Upper abdominal pain: especially under the ribs on the right side, which can signal HELLP syndrome or acute fatty liver
- Headache with visual changes: flashing lights, blurred vision, or spots, which point toward preeclampsia
- Fever over 101°F (38.3°C): which suggests an infectious cause that may need treatment
- Inability to keep fluids down for more than 12 hours: dehydration in the third trimester can reduce blood flow to the placenta
- Yellowing skin or eyes: a sign of liver dysfunction requiring emergency workup
- Decreased fetal movement: always worth reporting, regardless of whether you are vomiting
- Sudden severe onset: vomiting that goes from absent to constant over a few hours, especially with abdominal pain
If your vomiting is more of a slow annoyance, happening a few times a week without those warning signs, you are likely dealing with reflux or mechanical pressure. Mention it at your next prenatal visit, try the dietary and ginger-based strategies, and track whether it is getting worse. The vast majority of third-trimester vomiting resolves the moment the baby is delivered, which is both the most frustrating and the most reassuring thing anyone can tell you about it.