title: Maternal underweight and the risk of spontaneous abortion.
abstract: BACKGROUND
  To evaluate the risk of spontaneous abortion in relation to maternal pre-pregnant underweight.
  
  
  METHODS
  The study was designed as a cohort study within the framework of the Danish National Birth Cohort (DNBC). The participants were a total of 23 821 women recruited consecutively to the DNBC from October 1, 1997 to March 31, 1999 and interviewed subsequently. The pregnant women were recruited in first half of pregnancy and interviewed about pre-pregnant body size, obstetric history, exposures in pregnancy, and socio-demographic factors. Pregnancies were followed-up regarding spontaneous abortion. Relative risk of spontaneous abortion was calculated as Hazard Ratios using Cox regression with delayed entry.
  
  
  RESULTS
  The outcome measure was spontaneous abortion. The hazard ratio for spontaneous abortion in women with a pre-pregnant body mass index (BMI) below 18.5 was 1.24 (95% confidence limits 0.95-1.63) compared to women with pre-pregnant BMI 18.5-24.9. Women with a BMI of 25 or more had a smaller increase in risk of spontaneous abortion. Adjustment for maternal age, parity, previous miscarriages, and lifestyle factors did not affect the estimates substantially, neither did exclusion of women with metabolic or eating disorders.
  
  
  CONCLUSIONS
  These results indicate that pre-pregnant underweight may affect the risk of spontaneous abortion negatively.
authors.affiliation: Department of Social Medicine, Institute of Public Health, University of Copenhagen, Svanemøllevej 25, DK-2100 Copenhagen N, Denmark.
authors.forename: Stine
authors.initials: S
authors.lastname: Helgstrand
authors.forename: Anne-Marie Nybo
authors.initials: AM
authors.lastname: Andersen
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology* / Q000209:etiology; D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013851:Thinness / Q000150:complications*