Yes, sexual intercourse is generally very safe at 18 weeks of pregnancy, as your baby is well-protected by the amniotic sac. You should only avoid it if you have complications like unexplained vaginal bleeding, leaking amniotic fluid, or a history of preterm labor. For comfort, choose positions that avoid putting direct pressure on your abdomen. Regarding products, avoid vaginal douching, scented washes, and harsh chemical lubricants, as these can disturb your vaginal pH and cause infections. Instead, use simple, water-based, fragrance-free lubricants if needed. Always consult your obstetrician to ensure you have no specific personal contraindications.