Hypothyroxinemia and TPO-Antibody Positivity Are Risk Factors for Premature Delivery

Hypothyroxinemia and TPO-Antibody Positivity Are Risk Factors for Premature Delivery: The Generation R Study. Korevaar TI, Schalekamp-Timmermans S, de Rijke YB, Visser WE, Visser W, de Muinck Keizer-Schrama SM, Hofman A, Ross HA, Hooijkaas H, Tiemeier H, Bongers-Schokking JJ, Jaddoe VW, Visser TJ, Steegers EA, Medici M, Peeters RP. J Clin Endocrinol Metab. 2013 Nov;98(11):4382-90. doi: 10.1210/jc.2013-2855.
Premature delivery is an important risk factor for child mortality and psychiatric, metabolic, and cardiovascular disease later in life. In the majority of cases, the cause of prematurity cannot be identified. We investigated the relation between maternal serum thyroid parameters and the risk of premature delivery in a large prospective population-based study. Serum TSH, free T4 (FT4), T4, and TPO antibodies (TPOAbs) were determined during early pregnancy in 5971 pregnant women from the Generation R study. Data were available on maternal age, parity, smoking, socioeconomic status, ethnicity, maternal anthropometrics, and urinary iodine levels.:
Of all women, 5.0% had a premature delivery (<37 weeks), 4.4% had a spontaneous premature delivery, and 1.4% had a very premature delivery (<34 weeks). High TSH levels and subclinical hypothyroidism were associated with premature delivery but not with spontaneous premature delivery. Maternal hypothyroxinemia was associated with a 2.5-fold increased risk of premature delivery, a 3.4-fold increased risk of spontaneous premature delivery, and a 3.6-fold increased risk of very premature delivery (all P < .01). TPOAb positivity was associated with a 1.7-fold increased risk of premature delivery (P = .01), a 2.1-fold increased risk of spontaneous premature delivery (P = .02), and a 2.5-fold increased risk of very premature delivery (P = .04). These effects remained similar after correction for TSH and FT4 levels.
Conclusions: B oth hypothyroxinemia defined as freeT4 below the 2.5th percentile  (normal 14.3-25 pmol/L) and  and TPOAb positivity are associated with an increased risk of premature delivery. The increased risk in TPOAb-positive women seems to be independent of thyroid function.