Vomiting in the third trimester of pregnancy, which begins around week 28, can be an unexpected symptom. While nausea and vomiting are hallmarks of the first trimester, their reappearance late in pregnancy often causes concern. Late-term vomiting has a range of causes, from the normal physical stresses of a growing baby to rare but serious medical complications. This article explores the reasons behind this late-stage symptom, clarifying when it is manageable discomfort and when it requires immediate medical attention.
Common Physiological Causes
The most frequent causes of third-trimester vomiting relate directly to physical changes in the body. As the uterus expands to accommodate the baby, it exerts significant mechanical pressure on the abdominal organs. This crowding pushes the stomach upward, reducing its capacity and easily triggering feelings of fullness and vomiting after a meal.
Hormonal shifts also play a substantial role, particularly the continued presence of progesterone. Progesterone relaxes smooth muscles throughout the body to prevent premature contractions, and this effect extends to the digestive tract. This relaxation slows digestion and gastric emptying, meaning food remains in the stomach longer and increases the likelihood of reflux and nausea.
This muscular relaxation also affects the lower esophageal sphincter, the valve between the esophagus and the stomach. When this sphincter loosens, stomach acid travels back up into the esophagus, causing Gastroesophageal Reflux Disease (GERD), commonly known as heartburn. GERD is prevalent in late pregnancy, and in severe cases, the intense irritation can lead to vomiting. The return of nausea and vomiting may also be a late recurrence of morning sickness, driven by fluctuating pregnancy hormones like estrogen and human chorionic gonadotropin (hCG).
Serious Medical Conditions
While most late-term vomiting is benign, it can signal a serious underlying medical condition requiring urgent care. A primary concern is preeclampsia, a disorder characterized by high blood pressure and damage to organ systems, often the liver and kidneys. Sudden vomiting after the midpoint of pregnancy can be an advanced symptom, often accompanied by severe headaches, visual disturbances, or pain just below the ribs.
A more severe complication associated with preeclampsia is HELLP syndrome, which involves Hemolysis (red blood cell breakdown), Elevated Liver enzymes, and Low Platelet count. Liver involvement causes severe upper right-sided abdominal pain and tenderness. The worsening nausea and vomiting often feel like a severe case of the flu, and this condition is a medical emergency due to the risk of liver rupture and hemorrhage.
Acute fatty liver of pregnancy (AFLP) is an extremely rare, life-threatening liver disorder that manifests late in the third trimester. It involves excess fat accumulation in liver cells, leading to acute liver insufficiency. Symptoms begin with malaise, nausea, and vomiting, progressing rapidly to include jaundice and pain in the upper right abdomen.
Vomiting can also indicate severe dehydration or electrolyte imbalance, often resulting from a gastrointestinal virus or inability to keep fluids down. Less commonly, some people report nausea and vomiting during the onset of active labor, thought to be a physiological response to intense hormonal surges and strong uterine contractions.
Lifestyle and Dietary Management
For non-pathological causes of third-trimester vomiting, such as mechanical pressure and acid reflux, several management strategies can provide relief. Modifying eating habits to reduce food volume is effective; eating smaller, more frequent portions prevents the stomach from becoming overly full and mitigates pressure from the growing uterus.
Staying hydrated is important, but liquids should be consumed by sipping slowly between meals, not by gulping large amounts with food. This prevents stomach distension and reduces vomiting risk while combating dehydration. Identifying and avoiding trigger foods is beneficial, as high-fat, spicy, or acidic items take longer to digest and exacerbate reflux symptoms.
To manage nighttime GERD, elevating the head of the bed by six inches uses gravity to keep stomach acid down. Natural remedies like ginger (tea, lozenges, or supplements) and peppermint are widely used for their anti-nausea properties and can soothe the digestive tract.
Knowing When to Contact a Healthcare Provider
While occasional vomiting can be normal in late pregnancy, certain symptoms require immediate medical contact to rule out serious complications. An inability to keep down liquids for 12 hours or more is a serious warning sign, indicating a high risk of dehydration and electrolyte imbalance.
Symptoms suggesting a more serious underlying issue necessitate urgent medical evaluation:
- Severe, constant abdominal pain, especially focused in the upper right side of the belly.
- A severe, persistent headache that does not improve with over-the-counter pain medication.
- Any visual changes, such as blurring or seeing flashing lights.
- A sudden, significant increase in swelling of the face or hands.
- Fever or chills accompanying the vomiting.
- Any noticeable reduction in the baby’s usual movement patterns.