After 14 to 15 weeks, ending the pregnancy is more difficult because the fetus is larger and there is much greater blood flow to the uterus.

By the end of the fourth month, the fetus may be eight to ten inches in length and weighs a half pound or more.  She has begun to use her reflexes; sucking, swallowing, and blinking.  And an experienced sonographer might be able determine if your baby is a boy or a girl.

The ears are functioning, and there is evidence that the fetus hears quite a bit — the mother's voice and heartbeat as well as external noises.

The fetus listens to its mother's voice and heartbeat every day.

For more fetal development pictures, see:

• Fetal Development at 8 weeks
• Fetal development at 12 weeks
• Fetal development at 22 weeks

Picture copyright (c) Zrodlo Foundation, Krakow, Poland