Since your baby is preterm and vomited after consuming Aptamil Gold Infant Formula Stage 1 for the first time, do not continue feeding without medical advice. Vomiting in infants can occur for various reasons, but preterm babies have sensitive, immature digestive systems and often require formulas specifically designed for their needs. Please consult your paediatrician or neonatologist before giving this formula again. If vomiting persists, worsens, or is accompanied by poor feeding, lethargy, or dehydration, seek medical attention immediately.