Fetal Development at 14 Weeks of Gestation
At 14 weeks of gestation, the fetus has completed organogenesis and is entering a critical period of growth and functional development, with all major organ systems formed but continuing to mature.
Physical Development
- Size and Weight: The fetus measures approximately 8-10 cm in length (crown-rump) and weighs about 45 grams
- Organ Systems: All major organ systems have formed by this stage 1
- Skeletal Development: Bones are continuing to ossify, and limbs are fully formed with fingers and toes
- Facial Features: Eyes have moved from the sides to the front of the face, ears are in their final position, and facial features are becoming more defined
Neurological Development
- Brain Development: The brain is rapidly developing, with the cerebral cortex forming and neural pathways beginning to establish 1
- Movement: The fetus can make a variety of movements including flexion, stretching, and rolling movements, though the mother typically cannot feel these yet 2
- Sensory Development: Basic sensory functions are developing, with the fetus beginning to respond to external stimuli
Cardiovascular System
- Heart: The heart is fully formed and functioning, pumping approximately 24 liters of blood per day
- Circulation: The fetal circulatory system is established with the placenta serving as the respiratory organ
- Blood Flow: Umbilical artery Doppler assessments can detect continuous forward flow in the umbilical artery by this stage 1
Reproductive System
- Gender Differentiation: External genitalia are developed enough that sex can often be determined via ultrasound
- Hormone Production: In male fetuses, testosterone production is increasing and reaches a peak at 14-16 weeks, which is essential for male genital differentiation 1
Clinical Significance
- Screening: 14 weeks marks the end of the first trimester screening window for nuchal translucency evaluation and other markers of fetal aneuploidy 1, 3
- Anatomic Survey: Approximately 50% of major anatomical abnormalities can be detected between 11-14 weeks using a defined imaging protocol 4
- Medication Safety: After 14 weeks of gestation, administration of certain chemotherapy drugs becomes feasible if medically necessary, as the risk of major malformations decreases significantly after the first trimester 1
Imaging Capabilities
- Ultrasound Visualization: Transabdominal fetal anatomy scanning with standard views is possible with good reproducibility at this stage 5
- Tissue Harmonic and Compound Imaging: These techniques provide significantly better visualization of fetal anatomy compared to plain B-mode ultrasound 5
- Structures Visible: Most fetal anatomic regions can be visualized adequately, with neck structures scoring highest for visibility and cerebellar structures scoring lowest 5
Developmental Milestones
- Swallowing: The fetus can swallow amniotic fluid
- Breathing Movements: Fetal breathing movements are present, though lungs are not yet functional
- Sucking: The fetus has begun making sucking motions
Maternal-Fetal Relationship
- hCG Levels: Beta-hCG levels have begun declining from their peak at 8-10 weeks 3
- Placental Function: The placenta is fully functional, providing nutrients and oxygen to the fetus
- Maternal Recognition: At 14 weeks, ultrasound becomes the primary assessment tool for pregnancy evaluation rather than hormonal markers 3
This stage represents a critical transition from embryonic development to fetal growth and maturation, with all essential structures formed and continuing functional development.