When does morning sickness typically start during pregnancy?

When Does Morning Sickness Start in Pregnancy?

Morning sickness typically begins at 4-6 weeks of pregnancy, peaks at 8-12 weeks, and usually subsides by week 20. 1

Timing and Duration

• First appearance: Nausea and vomiting of pregnancy (NVP) usually begins around 4-6 weeks of gestation 1
• Peak intensity: Symptoms typically reach their maximum between 8-12 weeks 1
• Resolution: For most women (approximately 80%), symptoms improve or disappear by around week 20 1, 2
• Persistence: In about 10% of women, symptoms may persist throughout pregnancy and occasionally into the postpartum period 1

Prevalence and Severity

Morning sickness affects approximately 70-90% of pregnant women, making it one of the most common symptoms of pregnancy 1, 3. Despite its name, symptoms can occur at any time of day or night 2.

The severity of symptoms can be quantified using the Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score 1, 4:

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

Hyperemesis Gravidarum

In 0.3-3% of pregnancies, NVP progresses to hyperemesis gravidarum (HG), which is characterized by:

• Intractable vomiting
• Dehydration
• Weight loss >5% of pre-pregnancy weight
• Electrolyte imbalances 1, 3

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

Clinical Significance

Morning sickness may serve a protective function for both mother and embryo. Research suggests that women who experience morning sickness are significantly less likely to miscarry than those who do not 5. This protective effect may be related to:

1. Causing women to avoid potentially harmful foods during the critical period of embryonic organogenesis (weeks 6-18) 5
2. Protecting against foodborne pathogens during a time when pregnant women are relatively immunosuppressed 5

Management Considerations

Early intervention is important as symptoms can become more difficult to control once they progress 6. The American Gastroenterological Association recommends:

• Non-pharmacological approaches first:

  • Small, frequent, bland meals (BRAT diet: bananas, rice, applesauce, toast)
  • High-protein, low-fat meals
  • Avoiding triggers with strong odors 1, 4

• First-line medications when needed:

  • Vitamin B6 (pyridoxine) 10-25 mg every 8 hours
  • Doxylamine 10-20 mg at bedtime or every 8 hours
  • Ginger 250 mg capsule 4 times daily 1, 4

Early treatment of nausea and vomiting may help prevent progression to hyperemesis gravidarum 1.

Key Takeaways

• Morning sickness typically begins at 4-6 weeks gestation
• Symptoms usually peak at 8-12 weeks and resolve by week 20 for most women
• Despite the name, symptoms can occur at any time of day or night
• Early intervention with dietary changes and approved medications can help prevent progression to more severe forms