title: Seasonal trends of blood pressure during pregnancy in Japan: the babies and their parents' longitudinal observation in Suzuki Memorial Hospital in Intrauterine Period study.
abstract: OBJECTIVE
  Blood pressure (BP) increases both in winter and in the last trimester of pregnancy. Some interaction seems to exist between season and gestational age. The present study observed home BP values during pregnancy with adjustment for seasonal variation and gestational age.
  
  
  METHODS
  We observed 10353 home BP measurements from 101 normal pregnant women attending a maternity hospital in Japan. Home BP values were examined by mixed linear model adjusting for meteorological data and gestational age.
  
  
  RESULTS
  The lowest home BP values were observed in the second trimester [mean (+/-standard deviation) systolic/diastolic BP, 101.8 +/- 7.9/59.8 +/- 5.8 mmHg at gestational week 20]. In the last trimester, home BP values gradually increased and the values after gestational week 26 were significantly higher than those at gestational week 20 (110.1 +/- 9.7/66.8 +/- 7.7 mmHg at gestational week 40). A 10 degrees C increase in daily minimum outdoor temperature was associated with a mean reduction of 2.5/2.5 mmHg (Delta systolic BP/Delta diastolic BP: 95% confidence interval, 2.3/2.4 to 2.6/2.7 mmHg) in home BP with adjustment for gestational age. The largest and smallest estimated home BP changes during pregnancy were 12.8/12.5 and 3.1/3.0 mmHg in pregnant woman who delivered in January and July, respectively.
  
  
  CONCLUSIONS
  Interactions among BP, season and gestational age should be considered when evaluating BP in pregnant women. Risks associated with high BP might be underestimated in pregnant woman in summer who will deliver in winter.
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Tohoku University Graduate School of Pharmaceutical Sciences and Medicine, Sendai, Japan.
authors.forename: Hirohito
authors.initials: H
authors.lastname: Metoki
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Ohkubo
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Misato
authors.initials: M
authors.lastname: Nishimura
authors.forename: Yurie
authors.initials: Y
authors.lastname: Sato
authors.forename: Maiko
authors.initials: M
authors.lastname: Kawaguchi
authors.forename: Azusa
authors.initials: A
authors.lastname: Hara
authors.forename: Takuo
authors.initials: T
authors.lastname: Hirose
authors.forename: Taku
authors.initials: T
authors.lastname: Obara
authors.forename: Kei
authors.initials: K
authors.lastname: Asayama
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kikuya
authors.forename: Katsuyo
authors.initials: K
authors.lastname: Yagihashi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Matsubara
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Okamura
authors.forename: Shigeru
authors.initials: S
authors.lastname: Mori
authors.forename: Masakuni
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Imai
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D005260:Female; D005865:Gestational Age; D006801:Humans; D006973:Hypertension / Q000453:epidemiology / Q000208:ethnology; D007564:Japan; D016014:Linear Models; D008137:Longitudinal Studies; D008429:Maternal Welfare; D011247:Pregnancy / Q000502:physiology*; D011248:Pregnancy Complications / Q000453:epidemiology / Q000208:ethnology; D012307:Risk Factors; D012621:Seasons; D013696:Temperature