title: The effects of gestational transient thyrotoxicosis on the perinatal outcomes: a case-control study.
abstract: OBJECTIVE
  To study the effects of gestational transient thyrotoxicosis (GTT) on pregnancy outcomes.
  
  
  METHODS
  This case-control study retrospectively analyzed 7976 women with singleton pregnancies whose thyroid function was measured before 16 weeks of gestation and who delivered at ≥22 weeks of pregnancy. GTT was defined as hyperthyroidism (free thyroxine [FT4] level: ≥95th percentile) in the early pregnancy, which normalized in mid-pregnancy without thyroid-stimulating hormone receptor antibodies. Using data extracted from electronic records, we examined the association between GTT and the pregnancy outcomes (preterm delivery, gestational age at delivery, pregnancy induced hypertension (PIH), preeclampsia, placental abruption, caesarian section, birth weight, low birth weight, Apgar score, cord pH, stillbirth at gestational week ≥22, and neonatal death). We classified the cases into quartiles according to their FT4 values during the early pregnancy and investigated the association with the gestational age at delivery.
  
  
  RESULTS
  Two hundred and eight cases of GTT and 6317 cases with normal thyroid assessments were reviewed. GTT was associated with hyperemesis gravidarum, but not with stillbirth, preterm delivery, PIH, preeclampsia, placental abruption, or low birth weight. The gestation period was shorter in patients with GTT than in those with a normal thyroid function (38.69 ± 1.79 vs. 39.07 ± 1.64 weeks, p < 0.01). Higher FT4 levels during the early pregnancy were associated with earlier delivery (p = 0.02).
  
  
  CONCLUSIONS
  GTT was associated with a lower gestational age at delivery but not with adverse pregnancy outcomes. There was a negative correlation between the FT4 values in the early pregnancy and the gestational period.
authors.affiliation: Center of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Kinomoto-Kondo
authors.affiliation: Center of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan. umehara-n@ncchd.go.jp.
authors.forename: Nagayoshi
authors.identifier: http://orcid.org/0000-0002-6222-3942
authors.initials: N
authors.lastname: Umehara
authors.affiliation: Center of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan.
authors.forename: Shiori
authors.initials: S
authors.lastname: Sato
authors.affiliation: Center of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Ogawa
authors.affiliation: Department of Social Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Fujiwara
authors.affiliation: Center of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Arata
authors.affiliation: Center of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo, 157-8535, Japan.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sago
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D013971:Thyrotoxicosis / Q000150:complications*
keywords: Free T4; Gestational period; Gestational thyrotoxicosis; Hyperemesis gravidarum; Preterm delivery