New types of combined birth control pills -- containing both lower doses of oestrogens and newer progestogens -- may reduce the risk of ovarian cancer among young women, says a study.

The study, published in the journal The BMJ, showed that this positive effect strengthened with longer periods of use and persisted for several years after stopping."The reduced risk seems to persist after stopping use, although the duration of benefit is uncertain," the study said. At least 100 million women worldwide use hormonal contraception every day. 

For the study, the researchers from University of Aberdeen in Scotland and the University of Copenhagen in Denmark analysed data for nearly 1.9 million Danish women aged 15-49 years between 1995 and 2014.Women were categorised as never users (no record of being dispensed hormonal contraception), current or recent users (up to one year after stopping use), or former users (more than one year after stopping use) of different hormonal contraceptives.Most (86 per cent) of the hormonal contraceptive use related to combined oral products.The researchers found that the number of cases of ovarian cancer were highest in women who had never used hormonal contraception (7.5 per 100,000 person years), whereas among women who had ever used hormonal contraception, the number of cases of ovarian cancer were 3.2 per 100,000 person years.

The reduced risk for combined products was seen with nearly all types of ovarian cancer, and there was little evidence of important differences between products containing different types of progestogens."Based on our results, contemporary combined hormonal contraceptives are still associated with a reduced risk of ovarian cancer in women of reproductive age, with patterns similar to those seen with older combined oral products," the study authors said.Previous research had shown that the older products, containing higher levels of oestrogen and older progestogens, were tied to reduced ovarian cancer risk.But it was not known whether the newer contraceptives carried the same benefit.