Jacqueline E. Darroch and Susheela Singh at the Guttmacher Institute in New York said between 2003 and 12 the total number of women wanting to avoid pregnancy and in need of contraception increased from 716 million to 867 million, with growth concentrated among women in the 69 poorest countries where modern method use was already very low.
The study, published in The Lancet, found 73 percent of the 222 million women in developing countries who want to avoid a pregnancy but are not using a modern method now live in the poorest countries, compared with 67 percent in 2003.
Furthermore, women in the poorest countries who want to avoid pregnancy were one-third as likely to be using a modern method as those living in higher-income developing countries, the study said.
The researchers found between 2003 and 12 in the developing world, overall modern contraceptive use increased from 71 percent to 74 percent among women wanting to avoid pregnancy, though rates varied greatly among subregions.
Notable progress was made in Eastern Africa from 31 percent to 46 percent, Southern Africa from 75 percent to 83 percent, Southeast Asia from 64 percent to 72 percent, Central America at 71 percent to 77 percent and South America from 73 percent to 79 percent.
However, virtually no progress was made in the subregions with the lowest rates of use: in Middle Africa, contraceptive use increased only from 17 percent to 19 percent and in Western Africa from 22 percent to 26 percent.
'How to Train Your Dragon 2' releases 5-minute clip
Moore to attend retreat in to avoid Kutcher's wedding