Document Detail

Influence of gestational age and maternal height on fetal femur length calculations.
MedLine Citation:
PMID:  11339927     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To determine whether current methods of detecting Down syndrome based on fetal femur length calculations are influenced by gestational age or maternal height. METHODS: Four formulas were used to calculate expected femur length (FL) based on the fetal biparietal diameter (BPD) between 15 0/7 weeks' gestation and 19 6/7 weeks' gestation. For each gestational age, the BPD:FL ratio for women shorter than one standard deviation (SD) below the mean height was compared with the ratio for women taller than one SD above the mean height. A measured:expected FL ratio of 0.91 or less and a BPD:FL ratio greater than 1.5 SD above the mean was considered abnormal. RESULTS: The four formulas used to calculate measured:expected FL ratios were significantly more likely to be abnormal at 15--16 weeks' gestation, compared with 18-19 weeks' gestation (P <.05). Maternal height correlated with femur lengths at 18 and 19 weeks' gestation (P <.05) but not at earlier gestational ages. At 18 and 19 weeks' gestation, women shorter than one SD below the mean were twice as likely to have an abnormal BPD:FL ratio compared with women taller than one SD above the mean (relative risk 2.38; 95% confidence interval 1.21, 4.69). CONCLUSION: Early gestational age increases a woman's risk of having an abnormal measured:expected FL ratio, whereas short stature increases a woman's risk of having an abnormal BPD:FL ratio at later gestational ages. These findings indicate that risk assessment for fetal Down syndrome for such patients might be inaccurate. (Obstet Gynecol 2001;97:742-6.
B T Pierce; E G Hancock; C M Kovac; P G Napolitano; R F Hume; B C Calhoun
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Obstetrics and gynecology     Volume:  97     ISSN:  0029-7844     ISO Abbreviation:  Obstet Gynecol     Publication Date:  2001 May 
Date Detail:
Created Date:  2001-05-07     Completed Date:  2001-06-14     Revised Date:  2009-10-26    
Medline Journal Info:
Nlm Unique ID:  0401101     Medline TA:  Obstet Gynecol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  742-6     Citation Subset:  AIM; IM    
Department of Obstetrics and Gynecology, Madigan Army Medical Center,., Tacoma, Washington 98431, USA.
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MeSH Terms
Body Height*
Cohort Studies
Confidence Intervals
Down Syndrome / epidemiology,  ultrasonography*
Embryonic and Fetal Development
Femur / embryology*,  growth & development*
Gestational Age*
Predictive Value of Tests
Risk Assessment
Sensitivity and Specificity
Ultrasonography, Prenatal / methods*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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