Fatigue in the first trimester

By trimester

Weeks 1–13

1st trimester

Fatigue often peaks between weeks 8 and 14. It's driven by progesterone's sedating effect plus the metabolic work of building the placenta. Napping when you can, protecting your sleep, and staying lightly active with short walks all help.

What does the evidence show for fatigue in the first trimester?

• Fatigue is a common early-pregnancy symptom, driven mainly by the rise in progesterone. 1
• Iron needs rise substantially during pregnancy, to 27 mg a day, and iron-deficiency anemia is a common cause of worsening fatigue. 2
• Thyroid disorders are worth screening for when clinically indicated, since untreated hypothyroidism can cause worsening fatigue and other symptoms. 3
• Getting about 150 minutes of moderate aerobic activity a week is linked to better energy, sleep, and mood during pregnancy. 4
• Iron-deficiency anemia in pregnancy commonly presents with fatigue, palpitations, shortness of breath, dizziness, and pallor, and is generally flagged at a hemoglobin below 110 g/L in the first trimester and below 105 g/L in the second and third trimesters. 5

When should I call my provider about fatigue in the first trimester?

Fatigue that comes with shortness of breath, a racing heart, dizziness, or unusual paleness can point to iron-deficiency anemia, which is common enough in early pregnancy to be worth a same-day mention to your provider rather than waiting for your next visit. Anemia in pregnancy is generally flagged at a hemoglobin below 110 g/L in the first trimester, a number your provider checks with routine bloodwork. Fatigue this severe, especially paired with those other symptoms, deserves a blood check rather than being written off as normal tiredness. None of these lists replace your own judgment: if this symptom worries you, that on its own is enough reason to check in with your healthcare provider.