18 weeks is 4 months and 2 weeks, which is commonly considered the beginning of the fifth month of pregnancy. This stage is part of the second trimester.
Prenatal appointments are often scheduled about once a month during the second trimester. At 18 weeks, the baby may measure about 7 to 8 inches and weigh around 7 to 9 ounces. Some people may begin to feel the baby move or even hiccup at this stage.
Pregnancy is tracked in weeks rather than months because weeks provide a more accurate way to monitor the baby’s development. An OB-GYN or Certified Nurse-Midwife can calculate your gestational age, evaluate the baby’s development, and provide prenatal care throughout the pregnancy.