The third trimester of pregnancy, beginning around week 28, is often anticipated as a period of final preparation, but it can unexpectedly bring back a familiar discomfort: nausea. Many assume that the digestive distress known as “morning sickness” is strictly confined to the first trimester due to the initial surge of pregnancy hormones. However, for a significant number of expectant mothers, queasiness or outright vomiting can return during the final months. This late-stage nausea is a distinct experience from early pregnancy sickness, raising questions about its causes and significance as the body nears labor.
The Resurgence of Nausea
The short answer to whether nausea can return in the third trimester is yes; it is a relatively common experience. While the intense, hormonally-driven sickness often peaks between weeks nine and sixteen, symptoms can persist or reappear later. Studies suggest that between 15% and 20% of pregnant people report experiencing nausea that continues or returns in the third trimester.
This discomfort is usually a direct result of the dramatic physical changes occurring as the pregnancy progresses. The mechanisms driving third-trimester nausea are typically more mechanical and less purely hormonal than in the first trimester. Healthcare providers often normalize this experience, but it must be distinguished from the persistent, severe vomiting characteristic of hyperemesis gravidarum, which may continue throughout the entire pregnancy.
Physical and Hormonal Drivers of Late Nausea
Physical Compression
The primary causes of third-trimester nausea stem from the size of the growing uterus and its influence on the digestive tract. As the fetus reaches its maximum size, the uterus expands upward, exerting significant pressure on surrounding organs, including the stomach. This physical compression reduces the available space for the stomach to expand, leading to a feeling of fullness, discomfort, and subsequent nausea after small meals.
Hormonal Effects and Digestion
The hormone progesterone plays a continuous role by relaxing smooth muscles throughout the body, including those in the digestive system. This relaxation slows down gastric emptying, meaning food remains in the stomach for longer periods. The combination of a compressed stomach and slower digestion increases the likelihood of contents backing up into the esophagus, known as gastroesophageal reflux disease (GERD) or heartburn, which frequently manifests as nausea.
Hormonal fluctuations in the final weeks also contribute to digestive upset. While the initial human chorionic gonadotropin (hCG) surge subsides, estrogen levels continue to rise in preparation for labor. High levels of estrogen are known to irritate the stomach lining, which can trigger or exacerbate feelings of nausea. Even the intense movements of the growing fetus can occasionally cause a sharp discomfort or shift in internal pressure that is perceived as a wave of nausea.
Management and Comfort Strategies
Managing third-trimester nausea involves strategic adjustments to eating habits to minimize the impact of physical compression and slowed digestion. Consuming small, frequent meals throughout the day prevents the stomach from becoming overly full. Avoiding trigger foods, particularly those that are spicy, fatty, or highly acidic, also lessens the burden on the digestive system.
Positional adjustments provide relief by counteracting physical pressure and reflux. Remaining upright for at least an hour after eating helps gravity keep stomach contents in place, reducing acid reflux. When sleeping, elevating the head of the bed by six to nine inches can help prevent nighttime symptoms.
Staying well-hydrated is crucial, as dehydration can worsen nausea and discomfort. Sipping on clear fluids or water throughout the day, rather than drinking large amounts at once, is better tolerated. Natural remedies, such as ginger in the form of tea, candies, or supplements, can be soothing. Healthcare providers may also suggest Vitamin B6, often dosed at 25mg three times daily, to alleviate persistent nausea.
When Nausea Signals a Deeper Concern
While most third-trimester nausea is benign, its reemergence can occasionally signal a serious condition requiring immediate medical evaluation. Persistent, severe vomiting that prevents keeping down fluids for 24 hours is a red flag, as this can lead to severe dehydration. Signs of dehydration include reduced urination, dark-colored urine, and lightheadedness.
Nausea accompanied by other symptoms can be a warning sign of preeclampsia, a serious high blood pressure disorder that usually develops after 20 weeks. These concerning symptoms include:
- A new, severe headache that does not improve with standard pain medication.
- Sudden visual changes like blurred vision or seeing spots.
- Pain in the upper right side of the abdomen, related to the liver.
- A noticeable decrease in fetal movement.
Any sudden, sharp abdominal pain combined with nausea should prompt an immediate call to a healthcare provider. Conditions like preeclampsia or the related HELLP syndrome can progress quickly in the third trimester, making prompt recognition necessary for the safety of both the mother and the baby.