When Morning Sickness Starts in Pregnancy
Morning sickness typically begins at 4-6 weeks of gestation, peaks at 8-12 weeks, and resolves by week 20 in most women. 1, 2
Typical Timeline
Onset occurs at 4-6 weeks gestation in the majority of affected women, coinciding with rising human chorionic gonadotropin (hCG) levels 1, 2
Peak symptoms manifest at 8-12 weeks gestation, corresponding to the period when embryonic organogenesis is most susceptible to chemical disruption 2, 3
Resolution by week 20 occurs in most cases, though symptoms may persist longer in some women 1, 2
Symptoms can occur at any time of day or night, despite the term "morning sickness" 4
Prevalence and Clinical Significance
Nausea and vomiting affects 30-90% of pregnant women, making it one of the most common pregnancy symptoms 1
The pathophysiology involves elevated hCG and estrogen levels, along with progesterone-mediated delayed gastric emptying 1
Women who experience morning sickness have significantly lower miscarriage rates compared to those without symptoms, as demonstrated in 9 of 9 studies reviewed 3
Progression to Severe Disease
Hyperemesis gravidarum develops in 0.3-3% of pregnant women, representing the severe end of the spectrum 2, 4
This severe form is characterized by intractable vomiting, dehydration, and electrolyte imbalances, typically starting before week 22 of gestation 2
In 10% of hyperemesis cases, symptoms persist throughout pregnancy and occasionally into the postpartum period 2
Clinical Pitfall
The critical window is weeks 6-18 when organogenesis is most vulnerable, making early recognition and treatment essential to prevent progression to hyperemesis gravidarum, which requires hospitalization 1, 2. Do not dismiss early pregnancy nausea as benign—proactive management prevents severe complications.