title: The relationship between frequency of obstetric ultrasound scans and birthplace preference--a case control study.
abstract: OBJECTIVE
  to investigate the relationship between frequency of ultrasounds and birthplace preference.
  
  
  METHODS
  retrospective case-control study with the number of ultrasounds as the exposure and the pregnant woman's preference to give birth in a low-technology setting (midwifery-led unit or home) or a high-technology setting (obstetric unit) as the primary outcome.
  
  
  METHODS
  low-risk primigravid women receiving antenatal care at a central London academic medical centre.
  
  
  METHODS
  antenatal ultrasound frequency; birthplace preference at the initial pregnancy appointment (T1) and at the commencement of labour (T2); demographic data including ethnicity, index of multiple deprivation, age, and body mass index.
  
  
  RESULTS
  1100 cases were reviewed. Women received an average of 4.03 ultrasounds during their pregnancy (SD=1.96, range 2-14). The frequency of ultrasounds for women who had a low-technology T2 birthplace preference was significantly lower than for those who had a high-technology T2 birthplace preference (t=2.98, df=1098, p=0.003, r=0.1), and women who had a constant low-technology birthrate preference had significantly less ultrasounds than other women (F (3,644)=3.475, p=.02). However, within a logistic regression the frequency of ultrasound was not associated with T2 birthplace preference, after controlling for T1 birthplace preference.
  
  
  CONCLUSIONS
  the findings of this investigation suggest that a preference made early in pregnancy is a greater predictor of birthplace preference than exposure to antenatal ultrasounds.
  
  
  CONCLUSIONS
  further research is required to inform interventions that would encourage low-risk pregnant women to select a low-technology place of birth.
authors: Health Psychology Research Group, UCL Department of Clinical, Educational and Health Psychology, 1-19 Torrington Place, London WC1E 7HB, UK. Electronic address: james.m.harris@kcl.ac.uk.
authors: James Matthew
authors: JM
authors: Harris
authors: Department of Family Health Care Nursing, University of California, San Francisco, USA.
authors: Linda
authors: L
authors: Franck
authors: Institute of Women׳s Health, UCLH, UK.
authors: Belinda
authors: B
authors: Green
authors: Institute of Women׳s Health, UCLH, UK.
authors: Stephanie
authors: S
authors: Wilson
authors: Department of Clinical, Educational and Health Psychology, UCL, UK.
authors: Susan
authors: S
authors: Michie
mesh_terms: D000328:Adult; D016550:Birthing Centers / Q000592:standards*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D009035:Mothers / Q000523:psychology*; D009723:Nurse-Patient Relations; D011247:Pregnancy; D011295:Prenatal Care / Q000523:psychology* / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014463:Ultrasonography / Q000706:statistics & numerical data*
keywords: Low-risk pregnancy; Medicalisation; Place of birth choice; Ultrasound frequency