21 weeks

Boo now weighs about 360 grams. Up until now he has been measured from crown to rump but from this point on the measurement will be from crown to heel. And from crown to heel he is approximately 27 centimetres long. His eyebrows and eyelids are fully developed and the fingernails cover the fingertips. Boo can now hear our conversations. If we talk, read, or sing Boo, he can hear us. Some studies have found that newborns will suck more vigorously when read to from a book they heard frequently in utero.