Twins who are born after fertility treatment run an enhanced risk of health problems during their first three years of life, reveals a study conducted in Australia and UK.
The first study cited that twins born as a result of assisted reproductive technology (ART) are more likely to be admitted to neonatal intensive care, and to be hospitalised in their first three years of life than spontaneously conceived twins.
Already, ART twins are known to be at a higher risk of problems like low birth weight and premature delivery than singletons around the time of their birth, but until now there has been conflicting evidence about whether assisted reproduction itself is responsible for adding to the number of problems seen in ART twins.
Thus researchers aimed at perinatal outcomes and hospital admissions for all twin children born in Western Australia between 1994 and 2000, whether as a result of ART or spontaneous conception.
In the study, the researchers matched the ART twins with spontaneously conceived, non-identical twins of different sexes (referred to in the study as "unlike sex spontaneously conceived twins", or "ULS SC twins").
"We found that twins conceived following ART treatment had a greater risk of adverse perinatal outcome, including preterm birth, low birthweight and death, compared with spontaneously conceived twins of unlike sex. ART twins had more than double the risk of perinatal death compared to ULS SC twins, although the risk was similar to that of all SC twins, including identical twins," said Michele Hansen, from the Telethon Institute for Child Health Research in Western Australia.
"ART twins stayed longer in hospital than ULS SC twins at the time of their birth: an average of 12 days compared with eight days. ART twins were four times more likely to be admitted to neo-natal intensive care than ULS SC twins, and were more likely to be admitted to hospital during the first three years of their life.
"After adjusting for confounding factors such as year of birth, maternal age, parity and so on, ART twins still had a nearly two-thirds higher risk of being admitted to neo-natal intensive care, and a higher risk of being admitted to hospital in their first three years of life, although this was only statistically significant in their second year, when their risk was nearly two-thirds higher.
"Couples undergoing fertility treatment should be aware that, in addition to the known increased perinatal risks associated with a twin birth, ART twins are more likely than spontaneously conceived twins to be admitted to neonatal intensive care and to be hospitalised in their first three years of life," she added.
On the other hand, the second study, offered reassuring evidence on the outcome of children born after embryos were frozen and stored, before being thawed and transferred to the womb.
The results could be good news as almost 25 percent of ART babies worldwide, are now born after freezing or vitrification.
Led by Dr Ulla-Britt Wennerholm, an obstetrician at the Institute for Clinical Sciences, Sahlgrenska Academy (Goteborg, Sweden), the study reviewed the evidence from 21 controlled studies that reported on prenatal or child outcomes after freezing or vitrification.
It was found that embryos that had been frozen shortly after they started to divide had a better, or at least as good, obstetric outcome (measured as preterm birth and low birth weight) as children born from fresh cycles of IVF (in vitro fertilisation) or ICSI (intracytoplasmic sperm injection).
The malformation rates between the fresh and frozen cycles were found to be comparable.
The research has been published online in Europe's leading reproductive medicine journal Human Reproduction.