Search for: All records

Abstract PurposeIt remains unknown to what degree thyroid hormone replacement therapy (THRT) during and initiation after pregnancy determines pregnancy outcomes. The present study primarily aimed to quantify the impact of THRT patterns (including trajectories) on gestational age, birth weight, and head circumference of infants. The secondary aim was to compare results of trajectory with traditional analysis. MethodsWe combined data from the Norwegian Mother, Father and Child Cohort Study (MoBa) to other Norwegian registry data and the Norwegian Environmental Biobank. The study population included 54 020 women enrolled in MoBa in 2005 to 2008. On the basis of prescription records, we classified women into nonhypothyroid (n = 51 390; reference group), THRT after delivery (n = 1397), or medicated (n = 1233) groups. Applying Group‐Based‐Trajectory Models (GBTMs), we determined THRT trajectories among women in the medicated group. Propensity score weighting linked multiple treatment groups to pregnancy outcomes. ResultsPatterns were identified among women using medication during (Decreasing‐Low, Increasing‐Medium, Constant‐Medium, and Constant‐High) and after pregnancy. Women in the Increasing‐Medium (adjusted Odds Ratio [aOR] = 1.69; 95% Confidence Interval [CI], 1.06‐2.73) and the THRT after delivery (aOR = 1.19; 95% CI, 1.01‐1.42) groups had increased risk of giving birth to an LGA infant. In the traditional analysis, only women in the THRT after delivery group showed increased risk for an LGA infant (aOR = 1.19; 95% CI, 1.00‐1.42). We found no other differential effect among the five THRT patterns on the other outcomes. ConclusionsWomen with THRT after delivery or late onset THRT treatment showed increased risk of LGA infants.