Week 7 During Week 7 of pregnancy, or 5 weeks after conception, the brain is developing rapidly, with the 5 main sections established. The face is also quickly developing, and eye lenses, ear buds, and nostrils become visible. The arms and legs continue to grow with paddle-like shapes where the hands and feet will be. The main branches of the lungs are developing. The embryo is a quarter of an inch long.