The return of nausea and vomiting in the third trimester is a common, yet often surprising, experience for many people. While the familiar “morning sickness” is strongly linked to the first trimester’s surge in hormones, symptoms of digestive distress can reappear or intensify as the pregnancy progresses into its final stage. This late-stage discomfort is typically the result of a combination of mechanical pressure and ongoing hormonal shifts specific to the rapidly concluding pregnancy. Understanding the various causes, from simple physical changes to more serious underlying conditions, is helpful for managing symptoms and knowing when to seek immediate medical advice.
Physiological Causes of Late-Stage Nausea
The primary reasons for late-stage nausea are directly related to the physical size of the growing fetus and uterus. As the baby expands, the uterus pushes upward, significantly reducing the space available for the stomach and intestines.
This physical crowding often leads to delayed gastric emptying, where food remains in the stomach for longer periods. The slowed movement of food causes feelings of fullness, bloating, and subsequent nausea. The effect of a full stomach being physically compressed causes significant symptoms.
The pressure from the uterus also worsens gastroesophageal reflux disease (GERD), which affects up to nine out of ten pregnant individuals by the third trimester. GERD occurs when stomach acid backs up into the esophagus. This reflux is made easier by the relaxation of the lower esophageal sphincter, caused by high levels of the hormone progesterone. Progesterone acts to relax smooth muscles throughout the body, and the combination of acid reflux and physical crowding can easily trigger severe nausea and vomiting.
External and Non-Pregnancy Related Factors
Not all vomiting in the third trimester is directly related to the pregnancy itself. Acute bouts of vomiting and diarrhea may be caused by a simple foodborne illness or a common stomach virus.
These external insults can be more severe in pregnancy because the body’s digestive system is already under strain. Dehydration is a major concern with any illness and can occur more quickly in pregnancy. Simple dietary triggers, such as overly spicy, greasy, or large meals, can overwhelm the compromised digestive system, leading to nausea and vomiting.
When Vomiting Signals Urgent Medical Attention
While most late-stage nausea is benign, certain accompanying symptoms signal a need for immediate medical evaluation. The sudden onset of nausea and vomiting after the midpoint of pregnancy, especially when coupled with other symptoms, can be a warning sign for preeclampsia. Preeclampsia is a serious condition characterized by new-onset high blood pressure and signs of damage to the liver or kidneys.
If vomiting is accompanied by a severe, persistent headache, sudden changes in vision (such as blurring or flashing lights), or intense pain in the upper right side of the abdomen (below the ribs), contact a healthcare provider immediately. This combination can indicate a progression to severe preeclampsia or HELLP syndrome, which involves the breakdown of red blood cells, elevated liver enzymes, and low platelet count.
Persistent, severe vomiting that prevents keeping down liquids and leads to dehydration requires prompt medical attention. Signs of severe dehydration include dizziness, dark-colored urine, and an inability to urinate frequently. Furthermore, vomiting that occurs alongside rhythmic abdominal pain, persistent low back pain, or a feeling of pelvic pressure may indicate preterm labor.
Practical Strategies for Managing Nausea
Managing third-trimester nausea often involves making small, consistent adjustments to eating habits and lifestyle. Eating small, frequent meals rather than three large ones helps prevent the stomach from becoming overly full and putting more pressure on the uterus.
Avoiding foods known to trigger acid reflux, such as spicy, fatty, or highly acidic items, can reduce the severity of GERD-related nausea. Instead, focus on bland, easily digestible, carbohydrate-rich foods like crackers, toast, or rice.
Hydration is best managed by sipping fluids slowly throughout the day rather than drinking large amounts during meals, which quickly fills the compressed stomach. After eating, remaining upright for at least 30 minutes prevents stomach contents from refluxing into the esophagus. Elevating the head of the bed by six inches while sleeping can also help manage nighttime reflux and associated nausea.