Fetal macrosomia (also sometimes termed large for gestational age) is usually defined when the estimated fetal weight (EFW) is greater than the 90th percentile. According to this definition it affects up to 10% of all live births. Some also use an increased birthweight (i.e. greater than 4500g) in its definition.
Certain authors also use the 95th centile as the cut off and according to this definition ~5% of fetuses would be affected 8.
It typically presents in the 3rd trimester. There may be some predilection for male fetuses.
- inaccurate dating
- maternal obesity
- increased maternal height
- increased maternal age (over 35)
- maternal gestational diabetes
- previous LGA baby
Often manifests with truncal obesity and therefore the abdominal circumference (AC) will be one of the first parameters to increase. The AC is also considered one of the best parameters 8.
According to some reports, an EFW of >4000 g within a weeks window from birth along with an increased AFI ( >20 cm) and relevant clinical factors is associated with fetal macrosomia at birth in ~70% of cases 3.
Treatment and prognosis
Early delivery or elective Caesarian section are management options. Prognosis in a majority of cases is usually good.
Most complications are related to issues with delivery and include
- shoulder dystocia
- birth asphyxia
- neonatal hypoglycaemia (particularly in the setting of gestational diabetes)
- birth trauma (shoulder dystocia, brachial plexus injury)
- meconium aspiration
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- 2. Thorsell M, Kaijser M, Almström H et-al. Large fetal size in early pregnancy associated with macrosomia. Ultrasound Obstet Gynecol. 2010;35 (4): 390-4. doi:10.1002/uog.7529 - Pubmed citation
- 3. Pates JA, Mcintire DD, Casey BM et-al. Predicting macrosomia. J Ultrasound Med. 2008;27 (1): 39-43. J Ultrasound Med (full text) - Pubmed citation
- 4. Alessandri JL, Cuillier F, Ramful D et-al. Perlman syndrome: report, prenatal findings and review. Am. J. Med. Genet. A. 2008;146A (19): 2532-7. doi:10.1002/ajmg.a.32391 - Pubmed citation
- 5. Heiskanen N, Raatikainen K, Heinonen S. Fetal macrosomia--a continuing obstetric challenge. Biol. Neonate. 2006;90 (2): 98-103. doi:10.1159/000092042 - Pubmed citation
- 6. Henriksen T. The macrosomic fetus: a challenge in current obstetrics. Acta Obstet Gynecol Scand. 2008;87 (2): 134-45. doi:10.1080/00016340801899289 - Pubmed citation
- 7. Merz E, Bahlmann F. Ultrasound in obstetrics and gynecology. Thieme Medical Publishers. (2005) ISBN:1588901475. Read it at Google Books - Find it at Amazon
- 8. Entezami M, Albig M, Knoll U et-al. Ultrasound Diagnosis of Fetal Anomalies. Thieme. (2003) ISBN:1588902129. Read it at Google Books - Find it at Amazon