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HYPOTHYROIDISM IN PREGNANCY, o 1st trimester: < 2.5 mIU/L, o 2nd…
HYPOTHYROIDISM IN PREGNANCY
DEFINITION
Overt hypothyroidism: Elevated TSH plus low free T4 (FT4), or TSH > 10 mIU/L regardless of T4 levels.
Subclinical hypothyroidism (SCH): Elevated TSH with normal FT4.
Normal pregnancy alters normal ranges—TSH thresholds throughout trimesters are often lower: TSH > 2.5 mU/L in the first trimester, > 3.0 mU/L thereafter.
CLINICAL MANIFESTATIONS
Often subtle, especially in SCH—many signs mimic normal pregnancy
Possible signs: fatigue, weight gain, cold intolerance, dry skin, constipation, slowed reflexes.
COMPLICATIONS
Maternal risks:
miscarriage, anemia, pre-eclampsia, placental abruption, postpartum hemorrhage.
Fetal/neonatal risks:
preterm birth, low birth weight, neonatal respiratory distress, impaired neurodevelopment, lower IQ.
MANAGEMENT
•
First-line:
Levothyroxine (LT4) replacement therapy.
• Women already on LT4 should increase their dose by ~30–50% once pregnancy is confirmed.
•
Monitoring:
Check TSH (and ideally FT4) every 4–6 weeks until stable and then at least once each trimester.
•
TSH targets:
•
Treatment for SCH:
Typically recommended—especially if TPO antibodies are positive, TSH > 10 mIU/L, or other risk factors are present.
•
Iodine intake:
Ensure adequate iodine (recommended ~250 µg daily in pregnancy) to support thyroid hormone production.
o 1st trimester: < 2.5 mIU/L
o 2nd & 3rd trimesters: < 3.0 mIU/L