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Published on: June 29, 2013
Does a discrepancy between gestational age determined by biparietal diameter and last menstrual period sometimes
T Larsen1, T H Nguyen, G Greisen
1Department of Ultrasound, and Obstetrics and Gynaecology, Herlev Hospital, University of Copenhagen, Denmark.
Objective:
To assess the association between gestational age estimated from the last menstrual period (GA(LMP)) or from the biparietal diameter (GA(BPD)), and the subsequent birthweight for gestational age.
Design:
Population-based follow up study.
Setting:
Of 21,936 pregnancies contained in the ultrasound database, 16,387 singleton pregnancies with a reliable last menstrual period date and an ultrasound examination between 12 and 22 weeks of gestation were included.
Main Outcome Measures:
Correlation between: 1) birthweight deviation (birthweight-expected weight for gestation); 2) birthweight; and 3) pregnancy length and (GA(LMP)-GA(BPD)). Relative risk of birthweight < 2,500 g and low birthweight for gestation (> 22% below normal weight) related to five levels of discrepancy between (GA(LMP)-GA(BPD)).
Results:
(GA(LMP)-GA(BPD)) was not associated with deviation of birthweight related to GA(BPD). However the risk of low birthweight (< 2,500 g) and low birthweight for gestational age was significantly increased when (GA(LMP)-GA(BPD)) was > 7 days.
Conclusion:
A biparietal diameter smaller than expected from the last menstrual period date is mainly a problem of an error related to estimated time of ovulation. At the same time the relative risk of a low birthweight infant is slightly increased.