Maternal and fetal factors in breech presentation.

Area of Science:

• Obstetrics and Gynecology
• Fetal Medicine
• Perinatology

Background:

• Breech presentation, where the fetus is positioned lower than the head, is a common concern in late pregnancy.
• Previous theories suggested specific fetal and environmental factors were associated with breech presentation, but evidence was limited.

Purpose of the Study:

• To investigate fetal and environmental differences between fetuses in breech versus vertex presentations using ultrasound.
• To evaluate factors such as fetal growth, posture, placental site, and amniotic fluid volume.

Main Methods:

• Ultrasound screening at 33 weeks gestational age identified 228 pregnancies with breech fetuses.
• Fetal parameters were assessed at 33, 35, and 38 weeks.
• Comparison of breech and vertex presentations, including outcomes like gestational age and birth weight.

Main Results:

• No significant differences were found in extended fetal legs or cornual-fundal placental implantation between breech and vertex groups.
• Neonates born in breech presentation had a shorter gestational age (10 days less) and lower birth weight (4.9% less) relative to gestational age.
• Increased frequency of oligohydramnios, contracted pelvis, and uterine/fetal malformations observed in the breech group (15% of cases).

Conclusions:

• Extended fetal legs and specific placental implantation sites are not distinguishing factors for breech presentation.
• Breech presentation is associated with preterm delivery, lower birth weight, and potentially underlying fetal or maternal conditions.
• In the majority of breech presentations (85%), no single causative factor could be identified, indicating complex etiology.