title: Increased incidence of post-term delivery and Cesarean section after frozen-thawed embryo transfer during a hormone replacement cycle.
abstract: OBJECTIVE
  This study aimed to clarify the risks of adverse pregnancy outcomes in patients who conceive singletons after frozen embryo transfer (FET) during a hormone replacement cycle and their offspring.
  
  
  METHODS
  A retrospective cohort study was conducted in patients who conceived after FET, based on the Japanese-assisted reproductive technology registry for 2013. The perinatal outcomes in cases with live-born singletons achieved through natural ovulatory cycle FET (NC-FET) (n = 6287) or hormone replacement cycle FET (HRC-FET) (n = 10,235) were compared. Multiple logistic regression analyses were performed to determine the potential confounding factors.
  
  
  RESULTS
  The frequencies of macrosomia (1.1% in NC-FET and 1.4% in HRC-FET; P = 0.058) were comparable between patients after NC-FET and HRC-FET. The proportions of post-term delivery (0.2% in NC-FET and 1.3% in HRC-FET; P < 0.001) and Cesarean section (33.6% in NC-FET and 43.0% in HRC-FET; P < 0.001) were higher in patients after HRC-FET than in patients after NC-FET. The risks of post-term delivery (adjusted odds ratio (AOR) 5.68, 95% confidence interval (CI) 3.30-9.80) and Cesarean section (AOR 1.64, 95% CI 1.52-1.76) were also higher in patients after HRC-FET than in patients after NC-FET.
  
  
  CONCLUSIONS
  Patients who conceived singletons after HRC-FET were at increased risk of post-term delivery and Cesarean section compared with those who conceived after NC-FET.
authors.affiliation: Department of Perinatal Medicine and Maternal Care, National Center for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo, 157-8535, Japan.|Department of Comprehensive Reproductive Medicine, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8510, Japan.|Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, 157-8535, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Saito
authors.affiliation: Department of Reproductive Biology, National Research Institute for Child Health and Development, Tokyo, 157-8535, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Miyado
authors.affiliation: Department of Perinatal Medicine and Maternal Care, National Center for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo, 157-8535, Japan.|Department of Reproductive Biology, National Research Institute for Child Health and Development, Tokyo, 157-8535, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamatoya
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, 770-8503, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kuwahara
authors.affiliation: Division of Statistical Analysis, Center for Clinical Research and Development, National Center for Child Health and Development, Tokyo, 157-8535, Japan.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Inoue
authors.affiliation: Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, 157-8535, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Miyado
authors.affiliation: Department of Molecular Endocrinology, National Research Institute for Child Health and Development, Tokyo, 157-8535, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Fukami
authors.affiliation: Department of Comprehensive Reproductive Medicine, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8510, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Department of Perinatal Medicine and Maternal Care, National Center for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo, 157-8535, Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Saito
authors.affiliation: Department of Comprehensive Reproductive Medicine, Graduate School, Tokyo Medical and Dental University, Tokyo, 113-8510, Japan.
authors.forename: Toshiro
authors.initials: T
authors.lastname: Kubota
authors.affiliation: Department of Perinatal Medicine and Maternal Care, National Center for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo, 157-8535, Japan. saitou-hi@ncchd.go.jp.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Saito
mesh_terms: D002585:Cesarean Section / Q000379:methods; D015925:Cryopreservation; D004624:Embryo Transfer / Q000009:adverse effects*; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects*; D006801:Humans; D050498:Live Birth / Q000453:epidemiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*
keywords: Assisted reproductive technology; Cesarean section; Hormone replacement cycle; Post-term delivery