The aim of our study is to determine the range of frontal horn sizes (both upside and downside) in healthy fetuses over gestation and to determine how far FHs are from the midline . Also to determine the range of cavum septi pellucidi and Corpus callosum sizes . Also, to determine whether the maternal body mass index (BMI) affects rates of visualized and non-visualized CSP and CC.

Fetal central nervous system (CNS) abnormalities are among the most commonly encountered congenital abnormalities . Many different methods can be used to obtain prenatal diagnoses, including ultrasound (US), which is one of the most commonly used methods .Neonatal survival rates have increased over the last decades leading to increased number of infants with adverse neurodevelopmental outcomes, including cognitive, motor impairments and behavioral and learning difficulties later in life . Recent studies demonstrated that signs of abnormal neurological development are already present at birth .

Frontal horns (FHs) are the most anterior portions of the lateral ventricles, on each side the cavum septi pellucidi (CSP). In accordance with practice parameters released as early as 1985 by the American Institute of Ultrasound in Medicine, American College of Obstetrics and Gynecology, and Society of Radiologists in Ultrasound, the CSP is examined in screening fetal ultrasound (US) examinations in the biparietal diameter view . Frontal horns (FH) are also visualized in the same plane. Abnormal morphologic characteristics of the FHs such as enlargement, squaring, spearing, and splaying may have an association with congenital intracranial anomalies such as holoprosencephaly, schizencephaly and agenesis of the corpus callosum .

The corpus callosum (CC) is the largest interhemispheric white matter commissure of the human brain . It is a sensitive indicator of normal brain development and maturation

Inclusion Criteria:

• pregnant woman 15 weeks to 36 weeks

Exclusion Criteria:

• congenital malformations
• Multiple pregnancy
• intrauterine infection
• fetuses with Fetal growth restriction

All healthy pregnant women came to fetal medicine unit at 15 to 36 weeks