Assessment of Fetal Wellbeing in the Third Trimester
- Factors that may impact on fetal growth and wellbeing are indications for an ultrasound examination in the third trimester. These include: 1
- Pregnancy induced hypertension/pre-eclampsia
- Severe chronic renal disease + hypertension
- Maternal diabetes mellitus, pregnancy-induced diabetes mellitus
- Maternal vascular disorders
- Suspected, or previous history of intrauterine growth restriction
- Previous history of intrauterine fetal death
- Previous history of low-lying placenta
- Multiple pregnancy
- Clinical polyhydramnios
- Review of fetal anomaly
- Malpresentation
- Planned vaginal delivery of breech presentation
- Macrosomia describes a large fetus, with an estimated fetal weight greater than the 90th percentile after correcting for sex and ethnicity, or greater than 4500gm. This condition is associated with increased fetal and neonatal morbidity and mortality. Most complications are related to delivery, including shoulder dystocia, and birth trauma. Macrosomia associated with maternal diabetes carries a higher risk of intrauterine death. Close monitoring of fetal weight can be used to determine the optimal time for delivery. 1
- Intrauterine growth restriction (IUGR) refers to a fetus with an estimated fetal weight below the 10th percentile corrected for sex and ethnicity which has features of chronic hypoxia and/or malnutrition. However, a consensus does not exist for the definition of IUGR. It is associated with adverse fetal outcomes including acidosis, stillbirth, oligohydramnios, and low-birth weight; and adverse events during labour including fetal distress in labour. 1,2
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