In a study by Norwegian researchers, it has been revealed that the birth of triplets has increased 2.5 times as compared to the number in 1970. This research was reported in BJOG, an International Journal of Obstetrics and Gynecology, by Dr. Anne Tandberg of the Haukeland University Hospital in Bergen and her team.

According to this research, the increase is due to older aged mothers and ovulation-inducing drugs. It was also stated that in spite of practicing paternal care, the death rate for triplets is surprisingly ten times higher as compared to the single child.

For conducting this study, the researchers examined record of 2 million pregnant mothers in Medical Birth Registry of Norway, form the year 1967 to 2006. Due to ART and in vitro fertilization, during the period from 1987 and 1991, rate of triplet births was highest at 3.5 per 10,000 pregnancies. This number declined to 2.7 per 10,000 pregnancies after the new guidelines of single embryo implantation in IVF were implemented.

Also, according to the study, protracting the triplet pregnancy beyond the 28th week of gestation was stated as important as mortality rate is 50% before this state, while it is 3.8% with prolongation.