Assessment of thyroid function during pregnancy: the advantage of self-sequential longitudinal reference intervals

Area of Science:

• Endocrinology
• Reproductive Medicine
• Clinical Chemistry

Background:

• Thyroid function undergoes significant changes during pregnancy.
• Accurate monitoring of thyroid function is crucial for maternal and fetal health.
• Existing general gestation-specific reference intervals may not fully capture individual physiological variations.

Purpose of the Study:

• To evaluate the clinical utility of novel self-sequential longitudinal reference intervals (SLRI) for thyroid function during pregnancy.
• To compare SLRI with general gestation-specific reference intervals (GSRI) in terms of accuracy and misclassification rates.
• To assess the prevalence of maternal thyroid disorders.

Main Methods:

• Established two sets of reference intervals: SLRI (serum collected five times per case from 301 pregnant women) and GSRI (serum from 1455 subjects across trimesters).
• Utilized TSH levels from both interval types to screen 1744 pregnant women.
• Compared the percentage of potential misclassifications between SLRI and GSRI.

Main Results:

• Both SLRI and GSRI differed significantly from non-pregnant ranges (p < 0.05).
• SLRI demonstrated smaller interquartile ranges (IQR) than GSRI, particularly in the first trimester.
• Using SLRI reduced misclassification by 14.4% compared to GSRI's 1.3% misidentification rate.
• Subclinical hypothyroidism was the most common maternal thyroid disorder, affecting 0.11-3.84% of pregnant women.

Conclusions:

• SLRI accurately reflect dynamic changes in thyroid function throughout pregnancy.
• SLRI significantly decrease the potential for misclassifying thyroid dysfunction in pregnant individuals.
• Routine screening for thyroid dysfunction in pregnant women is essential and recommended.