Large fetal size in early pregnancy associated with macrosomia

Abstract

Objective: To assess if fetal size at the time of ultrasound dating examination is associated with the risk of macrosomia and complications associated with macrosomia.

Methods: This was a retrospective cohort study of 19 377 singleton pregnancies dated in gestational weeks 16-20 during the period 1998-2004 at Danderyd Hospital, Stockholm, Sweden. Obstetric outcome was assessed through linkage to the Swedish Medical Birth Register.

Results: When fetuses were > or = 7 days larger than expected at dating, compared with the expected size according to last menstrual period, there was a 59% increase in the risk of birth weight > or = 4500 g and a 145% increase in the risk of birth weight > or = 5000 g (odds ratio (OR), 1.59; 95% CI, 1.12-2.24 and OR, 2.45; 95% CI, 1.22-4.90, respectively). For a birth weight of > or = 4000 g the risk estimate was 1.19 (95% CI, 0.96-1.47).

Conclusion: Fetuses that are larger than expected in the second trimester have an increased risk of macrosomia. This emphasizes that fetal size in early pregnancy is not only a function of gestational duration, but also of fetal growth. However, only a limited proportion of all infants born macrosomic can be identified as such at the time of ultrasound dating.