Nausea in the Third Trimester: Uncommon but Present
Nausea in the third trimester is uncommon—it occurs in only approximately 16% of pregnant women and is not the typical pattern for pregnancy-related nausea. 1
Expected Timeline of Pregnancy-Related Nausea
The typical course of nausea and vomiting in pregnancy (NVP) follows a predictable pattern that is important to understand:
- Onset: 4-6 weeks of gestation
- Peak: 8-12 weeks of gestation
- Resolution: By week 20 in 90% of women 2, 1
By the third trimester, nausea should have resolved in the vast majority of pregnant women. The 2024 BJOG guideline explicitly states that NVP is defined as symptoms with "onset prior to 16 weeks of gestation" 2. The 2024 AGA guideline reinforces that NVP "subsides by week 20" 1.
Third Trimester Prevalence
When nausea does persist or occur in the third trimester:
- Weekly prevalence is approximately 16% 3
- Vomiting occurs in approximately 7% 3
- These symptoms appear occasionally and are not present for longer periods 3
This contrasts sharply with the 30-90% prevalence of nausea during early pregnancy 1.
Critical Clinical Caveat
If a patient presents with new-onset or persistent nausea in the third trimester, you must exclude other causes. This is not typical NVP. Consider:
- Acute fatty liver of pregnancy (AFLP): A rare but life-threatening condition that most commonly occurs in the third trimester, presenting with nausea, vomiting, and abdominal pain 4
- Preeclampsia/HELLP syndrome
- Gastroesophageal reflux (which IS common in late pregnancy, affecting ~60% of women) 3
- Gallstone disease
- Other acute abdominal pathology
The definition of NVP specifically requires that "there are no other causes" 2, making third-trimester nausea a red flag that warrants investigation rather than reassurance.
Hyperemesis Gravidarum Exception
For the minority (10%) of women with severe hyperemesis gravidarum (HG), symptoms can persist throughout pregnancy and occasionally into the postpartum period 1. However, even in HG cases, 80% improve by 20 weeks 1.
Bottom line: Third-trimester nausea is not the norm. While it can occur in about 16% of women, its presence—especially if new or severe—should prompt evaluation for alternative diagnoses rather than dismissal as typical pregnancy symptoms.