Routine Ultrasound at 30th-33rd weeks versus 30th-33rd and 35th-37th weeks in Low-Risk Pregnancies: A Randomized...

Area of Science:

• Perinatal Medicine
• Maternal-Fetal Medicine
• Diagnostic Ultrasound

Background:

• Fetal growth restriction (FGR) detection is crucial for optimizing perinatal outcomes.
• Evaluating the accuracy of late-term ultrasound for FGR screening is essential.
• Assessing the impact of timing of ultrasound on perinatal outcomes is important.

Purpose of the Study:

• To evaluate the accuracy of 35-37 weeks' ultrasound for fetal growth restriction (FGR) detection.
• To determine the impact of adding a 35-37 weeks' ultrasound on perinatal outcomes compared to only 30-33 weeks' ultrasound.

Main Methods:

• A randomized controlled trial involving 1,061 low-risk pregnant women.
• Control group: ultrasound at 30-33 weeks. Study group: ultrasounds at 30-33 and 35-37 weeks.
• FGR defined as estimated fetal weight (EFW) below the 10th percentile.

Main Results:

• Ultrasound at 35-37 weeks demonstrated 94% accuracy for FGR screening.
• Higher correlation between EFW and birthweight centile at 35-37 weeks (ρ = 0.75) vs. 30-33 weeks (ρ = 0.44).
• The study group (additional late ultrasound) had significantly lower rates of operative vaginal delivery (24.4% vs. 39.3%) and cesarean delivery for nonreassuring fetal status (16.8% vs. 38.8%).

Conclusions:

• Late-term ultrasound (35-37 weeks) is highly accurate for FGR detection.
• This later ultrasound shows improved correlation between estimated fetal weight and actual birth weight.
• Incorporating a 35-37 weeks' ultrasound is associated with reduced adverse perinatal outcomes.