When does nausea typically start in pregnancy?

When Does Nausea Start in Pregnancy?

Nausea in pregnancy typically begins at 4-6 weeks of gestation, peaks at 8-12 weeks, and usually subsides by week 20 for most women. 1

Timing and Prevalence

Nausea and vomiting of pregnancy (NVP) is extremely common, affecting approximately 70-90% of pregnant women. The pattern typically follows:

• Onset: Usually begins around 4-6 weeks of gestation
• Peak intensity: Occurs between 8-12 weeks
• Resolution: Most cases resolve by week 20
• Duration: For about 10% of women, symptoms may persist throughout pregnancy

Causes of Pregnancy Nausea

While the exact etiology remains incompletely understood, several factors likely contribute:

• Hormonal changes: Elevated levels of human chorionic gonadotropin (hCG) and estrogen
• GI motility changes: Progesterone has an inhibitory effect on gastrointestinal and small bowel motility, leading to delayed gastric emptying
• Genetic factors: Recent research has implicated placental proteins (GDF15 and IGFBP7) and hormone receptors in the etiology 2

Severity Assessment

The severity of nausea and vomiting can be quantified using the Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score:

• Mild: Score ≤6
• Moderate: Score 7-12
• Severe: Score ≥13

This assessment considers:

• Duration of nausea (hours per day)
• Frequency of vomiting episodes
• Frequency of retching/dry heaves

Progression to Hyperemesis Gravidarum

For approximately 0.3-2% of pregnant women, NVP progresses to hyperemesis gravidarum (HG), characterized by:

• Intractable vomiting
• Dehydration
• Weight loss >5% of pre-pregnancy weight
• Electrolyte imbalances

HG typically starts before week 22 of gestation, with symptoms resolving in >50% of affected women by week 16 and in 80% by week 20 1.

Management Considerations

Early recognition and treatment of nausea and vomiting in pregnancy is important as it may reduce progression to hyperemesis gravidarum. Initial management includes:

1. Dietary modifications:

   • Small, frequent meals
   • Bland foods (BRAT diet: bananas, rice, applesauce, toast)
   • High-protein, low-fat meals
   • Avoiding trigger foods and strong odors

2. First-line pharmacologic options (if needed):

   • Vitamin B6 (pyridoxine) 10-25 mg every 8 hours
   • Doxylamine (alone or in combination with pyridoxine)
   • Ginger supplements (250 mg four times daily)

Key Points to Remember

• Morning sickness is a misnomer as symptoms can occur at any time of day or night
• Early intervention may prevent progression to more severe forms
• Nausea in pregnancy is associated with normal pregnancy outcomes in most cases
• For most women, symptoms are self-limiting and resolve by mid-pregnancy
• Severe, persistent symptoms warrant medical evaluation to rule out hyperemesis gravidarum or other conditions

For women with history of severe nausea in previous pregnancies, early intervention may be particularly important, as there is often a pattern of recurrence in subsequent pregnancies.