The third trimester, which begins around the 28th week of pregnancy, is often anticipated as a period of final preparation for birth. While many people associate nausea and vomiting—commonly referred to as “morning sickness”—with the first trimester, an unexpected return of queasiness late in pregnancy can be unsettling. This late-term nausea affects an estimated 15 to 20 percent of pregnant people. Understanding the distinct causes of third-trimester nausea is important for knowing when to employ simple relief strategies and when to seek medical advice.
Understanding Late-Term Nausea
The return of nausea in the final months of pregnancy is often a result of physical and hormonal shifts. One primary cause is the sheer size of the growing uterus, which exerts significant pressure on the surrounding organs. As the baby expands, the stomach and digestive tract are compressed, which can easily trigger feelings of nausea and indigestion.
This physical crowding often contributes to or worsens gastroesophageal reflux disease (GERD), commonly known as heartburn. High levels of the hormone progesterone relax the valve connecting the esophagus and stomach. The increased abdominal pressure makes acid reflux more likely, causing stomach acid to back up into the esophagus and manifest as a persistent sensation of nausea.
Pregnancy hormones also slow down the entire digestive process, known as decreased gastric motility, meaning food stays in the stomach longer. This slowed transit time can lead to feelings of uncomfortable fullness, bloating, and gas, contributing to queasiness. Hormonal fluctuations remain a factor, and the shifting balance of hormones as the body prepares for labor can directly affect digestive sensitivity, sometimes re-triggering early pregnancy nausea.
Strategies for Relief and Comfort
Managing the common, non-threatening causes of third-trimester nausea often involves simple, consistent adjustments to daily habits. Eating smaller portions more frequently throughout the day is highly effective because it prevents the stomach from becoming overly distended due to reduced abdominal space. Focus on bland, easily digestible, and carbohydrate-heavy foods like crackers, toast, or rice, while avoiding anything spicy, greasy, or heavily seasoned that could irritate the stomach lining.
Hydration is also important, as dehydration can exacerbate nausea. Sipping on water, clear broths, or herbal teas with ginger or peppermint throughout the day can help settle the stomach. Avoid drinking large quantities of fluid with meals to prevent excess fullness.
Positional changes can reduce reflux-related nausea. Avoid lying down immediately after eating, and sleep with the head and upper body slightly elevated to help keep stomach acid down. If symptoms persist, discuss the use of over-the-counter antacids with a medical professional first.
When Nausea Signals a Serious Issue
While most late-term nausea is benign, its sudden onset or presence alongside other symptoms can indicate a serious pregnancy complication requiring immediate attention. The most significant concern is pre-eclampsia, a condition characterized by high blood pressure and signs of organ system damage, often the liver or kidneys. Nausea and vomiting can be a symptom of pre-eclampsia, especially when accompanied by a severe headache that does not improve with medication, changes in vision such as blurred sight or seeing flashing lights, or sudden, notable swelling in the hands and face.
Another serious, though rare, condition is HELLP syndrome, which is often considered a variant of severe pre-eclampsia and is a medical emergency. Nausea and vomiting are key symptoms of HELLP, which stands for Hemolysis, Elevated Liver enzymes, and Low Platelet count. The nausea is typically severe and may be accompanied by intense pain in the upper right side of the abdomen, which is where the liver is located.
Any persistent, severe vomiting that prevents the ability to keep down food or fluids should prompt a call to a healthcare provider due to the risk of dehydration. Nausea that occurs alongside signs of preterm labor, such as regular contractions, vaginal bleeding, or a sudden gush of fluid, should be evaluated immediately. If any of these concerning symptoms are present, contact a doctor or go to the emergency room immediately.