Abstract
Introduction
The aim of this study was to determine the extent to which regular monitoring of maternal
free thyroxine level and pregnancy-adapted L-thyroxine replacement therapy before
and during
pregnancy in patients with existing or newly diagnosed latent and manifest hypothyroidism
as well as hypothyroxinemia can influence the rate of premature births.
Materials and Methods
This is a retrospective cohort study assessing 1440 pseudonymized survey questionnaires
to evaluate the risks of premature birth with two study groups from the same medical
practice, and
a nationally recruited control group. Study group A (n = 360) had already been taking
L-thyroxine prior to conception, study group B (n = 580) started taking it after conception.
Both
study groups had a maximum gestational age of 12 + 0 GW. In the study groups, TSH
and free thyroxine levels were determined regularly for dose adjustment purposes.
The aim was to keep the
free thyroxine level in the euthyroid hyperthyroxinemic range within the pregnancy
adapted reference range. The control group (n = 500) had taken L-thyroxine during
pregnancy according to
criteria that were not known, as the questionnaire did not include any questions regarding
this matter. Taking other risk factors into account, the influence of pregnancy-adapted
L-thyroxine replacement therapy on the rate of premature births was determined using
logistic regression analysis.
Results
Compared with the control group, the premature birth rate was 70% lower (p < 0.0001)
in study group A and 42% lower in study group B (p = 0.0086), while the odds ratio,
at 3.46, was
particularly significant in study group A. High blood pressure (odds ratio 5.21),
body mass index per kg/m2 (odds ratio 0.91) and S. p. premature birth were identified as other
independent risk factors.
Conclusion
The results show an association between more intensive thyroid diagnostics and pregnancy-adapted
L-thyroxine replacement therapy and a decrease in premature births. Further studies
should
be conducted to confirm these results.
Keywords
premature birth - hypothyroidism - thyroxine - hypothyroxinemia - obstetrics
