A discrepancy between gestational age estimated by last menstrual period and biparietal diameter may indicate an increased risk of fetal death and adverse pregnancy outcome.

OBJECTIVE: To determine if the discrepancy between gestational age estimated by last menstrual period and by biparietal diameter (GALMP - GABPD) is associated with adverse pregnancy outcome.
DESIGN: Population-based follow up study. POPULATION: Singleton pregnancies were studied when a reliable date of last menstrual period and biparietal diameter measured between 12 and 22 weeks of gestation was available (n = 16,469).
METHODS: Logistic regression analysis and Kaplan-Meier survival analysis were used to analyse the association between GALMP - GABPD and adverse pregnancy outcome. MAIN OUTCOME MEASURES: Adverse outcome was defined as abortion after 12 weeks of gestation, still-birth or postnatal death within one year of birth, delivery < 37 weeks of gestation, a birthweight < 2,500 g or a sex-specific birthweight lower than 22% below the expected.
RESULTS: The risk of death was more than doubled if GALMP - GABPD of > or = 8 days was compared with GALMP - GABPD of < 8 days (OR 2.2; 95% CI 1.6-3.1). The risk of death was a factor of 6.1 higher if GALMP - GABPD of > or = 8 days was combined with increased (> 2 x multiple of median) maternal alpha-fetoprotein measured in the 2nd trimester.
CONCLUSIONS: A discrepancy between GALMP and GABPD generally reflects the precision of the two methods used to predict term pregnancy. However, a positive discrepancy of more than seven days, particularly with high maternal alpha-fetoprotein, might indicate intrauterine growth retardation and an increased risk of adverse perinatal outcome.