How the baby's organs and senses develop, and the continuing formation of the placenta.
- The second trimester begins 12 weeks into a pregnancy.
- During the second trimester, the foetus develops basic hearing.
- The sex of a foetus can be determined after 17 weeks using ultrasound.
- By week 24, the foetus is between 28 and 35cm long and weighs just under 1kg.