When does fatigue typically occur during pregnancy?

When Fatigue Typically Occurs During Pregnancy

Fatigue is most pronounced during the first trimester of pregnancy, typically beginning around 6-12 weeks, and often returns in the third trimester, while the second trimester usually offers some relief from fatigue symptoms. 1, 2

First Trimester Fatigue

• Fatigue is one of the earliest and most common symptoms of pregnancy, with studies showing significantly higher fatigue scores in women during the first trimester compared to non-pregnant women 1
• First trimester fatigue typically begins around 4-6 weeks of pregnancy and peaks between 8-12 weeks 3, 4
• Approximately 94.2% of pregnant women experience some degree of fatigue during pregnancy, with the first trimester being a particularly challenging period 2
• Younger maternal age and lower pre-pregnancy levels of iron, ferritin, and hemoglobin are associated with increased first trimester fatigue 5

Physiological Causes of Early Pregnancy Fatigue

• The first trimester fatigue is primarily attributed to the dramatic hormonal changes occurring during early pregnancy 4
• Increased progesterone levels, which have sedative-like effects, contribute significantly to early pregnancy fatigue 4
• The body experiences increased oxygen consumption and metabolic demands to support fetal development, which can deplete energy reserves 4
• Nausea and vomiting of pregnancy (NVP), which typically begins at 4-6 weeks and peaks at 8-12 weeks, can exacerbate fatigue due to decreased nutritional intake and disrupted sleep 3

Second Trimester Relief

• Many women experience a reduction in fatigue during the second trimester (weeks 13-26) as the body adapts to hormonal changes 5
• The placenta takes over hormone production, and nausea/vomiting typically subsides by week 20, which can improve energy levels 3
• Despite this general improvement, some women continue to experience moderate fatigue throughout pregnancy 2

Third Trimester Fatigue Return

• Fatigue often returns and intensifies during the third trimester (weeks 27-40) 2, 5
• The mean fatigue score progressively increases from the first trimester (23.53) to the second (25.78) and third trimesters (26.46) 2
• Third trimester fatigue is strongly associated with reduced total sleep time, as physical discomfort, frequent urination, and fetal movements disrupt sleep 5
• The increasing physical burden of carrying the growing fetus contributes to energy depletion and fatigue 6

Sleep Quality and Fatigue

• There is a significant inverse correlation between fatigue and sleep quality throughout pregnancy - as fatigue increases, sleep quality decreases 2
• Pregnant women typically report needing more sleep hours than non-pregnant women (8 hours vs. 7 hours) 1
• Sleep disturbances due to physical discomfort, frequent urination, and hormonal changes contribute to persistent fatigue 5

Work and Environmental Factors

• Work-related stress and adverse working conditions can exacerbate pregnancy fatigue and potentially impact pregnancy outcomes 6
• Healthcare providers should recognize fatigue as a significant issue during pregnancy and counsel women about preparing their work and home environments to achieve adequate rest, especially during the first trimester 5, 6

Clinical Implications

• Severe fatigue during pregnancy has been associated with increased risks of preterm labor, prolonged labor, cesarean section, and postpartum depression 2
• Postpartum fatigue is related to reduced sleep and low levels of ferritin and hemoglobin, suggesting the importance of addressing these factors during pregnancy 5
• Early intervention for symptoms like nausea and vomiting may help reduce fatigue progression, as these symptoms often coincide with peak fatigue periods 3