Thyroid function and autoantibody status among women who spontaneously deliver under 35 weeks of gestation.
OBJECTIVE
Recent studies report an association between maternal thyroid auto-antibodies and preterm birth. None have made the important distinction between spontaneous and iatrogenic preterm birth. We investigated the association between spontaneous preterm birth before 35-week gestation and both thyroid function and auto-antibody status.


METHODS
Retrospective nested case-control study, samples retrieved from a biobank of around 8000 samples.


METHODS
Forty-six cases of spontaneous preterm birth <35-weeks gestation compared with 124 cases who delivered at 40 weeks gestation, matched for maternal age and duration of serum storage. All resulted in a singleton liveborn.


METHODS
First trimester serum levels of TSH, free T4, free T3, anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies.


RESULTS
Women who had a preterm birth delivered at a median gestational age of 33 (+1 day) weeks gestation (controls 40 + 3 weeks) and had significantly lower birthweight infants [mean (range) weight 1965 (581-3117) grams compared with controls 3526 (2685-4760) grams]. Median levels of anti-thyroglobulin and anti-TPO antibodies were similar in the two groups (Anti-Tg: 3 IU/ml (Range 1-316) v 3 IU/ml (1-691); Anti-TPO 8 IU/ml (3-73) v 9 IU/ml (3-499); P >/= 0.18 for both comparisons, compared using three statistical models). In the preterm group, the median TSH level was 0.70 mIU/l (range 0.04-3.84), similar to controls (0.88 (0.01-2.87), P = 0.1). Free T3 and T4 levels were also similar in both groups.


CONCLUSIONS
Thyroid function and thyroid autoantibody status among women who have a spontaneous preterm delivery before 35 weeks gestation are not different from women delivering at term.
Tierney
Kelly
K
Department of Obstetrics and Gynaecology, Monash Institute of Medical Research, Monash University, Victoria, Australia.
Delpachitra
Pavitra
P
Grossmann
Mathis
M
Onwude
Joseph
J
Sikaris
Ken
K
Wallace
Euan M
EM
Hamilton
Emma J
EJ
Tong
Stephen
S
D000328:Adult; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007453:Iodide Peroxidase / Q000276:immunology; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood; D047928:Premature Birth / Q000097:blood* / Q000276:immunology*; D013960:Thyroid Function Tests; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D001323:Autoantibodies; C006606:anti-thyroglobulin; D014284:Triiodothyronine; D007453:Iodide Peroxidase; D013974:Thyroxine