The population of Egypt has reached 100 million, with a new baby being born roughly every 18 seconds.Prime Minister Mostafa Madbouly said last week that overpopulation was the single biggest challenge facing Egypt.President Abdul Fattah al-Sisi has described it as being equal to terrorism as a threat.Recently, the authorities have brought in measures to try to encourage people to have smaller families.The population has skyrocketed in the past three decades - from 57 million in 1990.