Cleft lip, often occurring with or without a cleft palate, is one of the most common congenital malformations, affecting approximately 1 in 700 live births worldwide. This condition, known broadly as an orofacial cleft, occurs when the tissues that form the upper lip do not fully join during early development in the womb, leaving an opening or split. Prenatal ultrasound is the primary non-invasive method for detecting this structural difference, using sound waves to create images of the developing fetus. This allows for the detailed examination of the fetal face for any discontinuity in the lip structure, helping healthcare providers and parents prepare for specialized postnatal care.
Gestational Timing for Detection
The facial structures must be sufficiently developed for visualization. Although the lip forms between the fourth and seventh weeks of pregnancy, the small size of the features early on makes detection difficult. The earliest possible time for suspicion of a cleft lip is around 12 to 13 weeks of gestation, often requiring advanced ultrasound technology.
The optimal window for a definitive visual assessment is during the mid-pregnancy anatomy scan, typically performed between 18 and 22 weeks. By this time, the fetal face is large enough, and the surrounding amniotic fluid provides a clear acoustic window for detailed imaging. Assessing the structural integrity of the upper lip is a standard part of this detailed second-trimester screening.
Specialized Ultrasound Techniques
Standard two-dimensional (2D) ultrasound is the initial and most common screening technique, providing a cross-sectional view of the fetal anatomy. To detect a cleft lip, the sonographer uses specific viewing angles to assess the integrity of the upper lip and nose. The coronal view, a frontal image of the face, is particularly useful for visualizing the lip and nostril area.
The axial view, a transverse cross-section of the face, allows for the examination of the maxillary alveolar ridge. If a cleft is suspected on the routine 2D scan, three-dimensional (3D) ultrasound is often used as a supplementary tool for confirmation. The 3D technique provides a surface-rendered image that is easier to interpret, offering a clearer, more realistic view of the facial defect and its extent.
Visual Signs of Cleft Lip
The most identifiable sign of a cleft lip on an ultrasound is the interruption of the continuous line that should form the upper lip. On a 2D image, this discontinuity typically appears as a vertical hypoechoic region, or a darker gap, extending through the fetal upper lip. The cleft can range from a small notch to a complete separation that reaches up into the nostril.
A cleft affecting only one side is a unilateral cleft, while a defect on both sides is a bilateral cleft. In cases of a complete cleft, the separation extends through the lip and the alveolar ridge. A bilateral cleft lip, especially one that includes the palate, often presents with a noticeable protrusion of the premaxilla, the central part of the upper jaw. This protrusion is visible as an echogenic mass below the nose.
Diagnosing a cleft lip is more straightforward than detecting an isolated cleft palate, as the lip is a surface structure more readily visualized. When the lip is involved, there is an approximate 50% chance that a cleft palate is also present. The presence of a cleft lip prompts a dedicated search for palate involvement, as the full extent of the defect is important for treatment planning.
Accuracy and Post-Diagnosis Steps
The accuracy of prenatal ultrasound in detecting cleft lip varies depending on factors such as fetal position, equipment quality, and the skill of the sonographer. Detection rates are generally higher for cleft lip than for isolated cleft palate. Furthermore, detection is significantly more likely for a complete cleft than for an incomplete or microform cleft, where the defect is smaller.
If a cleft lip is suspected during routine screening, the next step is often a referral for a specialized, or level II, ultrasound for confirmation. This scan is typically performed by a maternal-fetal medicine specialist for a more detailed assessment. Following confirmation, the medical team usually recommends genetic counseling to explore the possibility of an associated genetic syndrome.
Parents are also referred to a multidisciplinary craniofacial team, which includes surgeons, orthodontists, and other specialists, to begin planning for postnatal care. Early diagnosis allows the family to understand the condition, prepare for potential feeding challenges, and establish a comprehensive treatment plan involving surgical repair in the first few months of life.