Transfer of embryos cultured until blastocyst stage during in-vitro fertilization (IVF) may be associated with an increased risk of perinatal outcomes of the infants and the likelihood of having of same-sex twins, reports a recent study.
The study which was based on the large cohort of the Committee of Nordic ART and Safety (CoNARTaS) has found that blastocyst transfer is associated with a higher risk of preterm birth (before 37 weeks), and large-for-gestational-age rates. “These results are important,” say the investigators, ‘since an increasing number of all ART treatments are performed with blastocyst transfer.”
According to the study, the rate of infants born large for gestational age was 4.3% for those conceived after blastocyst transfer compared to a 3.7% for cleavage-stage transfers.
The study which involved nearly 90,000 assisted reproduction (ART) births, also reported a higher chance of having same-sex twins, reported Anne Laerke Spangmose, MD, of Copenhagen University Hospital in Denmark.
The incidence of having twins was reported to have increased from 2.3% following fresh cleavage-stage transfers to 4.0% with fresh blastocyst transfers.
“I would say this is a large increase,” Spangmose said in a statement, “considering the risks of perinatal and obstetric outcomes in twin births.”
Blastocyst transfer has become increasingly common in fertility clinics in recent years, with prior research showing that transferring these longer, better developed embryos boosts the chances of pregnancy and live birth.
Spangmose acknowledged that blastocyst culture plays a crucial role in ART treatment. “But we still need to consider whether blastocyst transfer should be the gold standard in fresh ART cycles given the adverse risks found in our study,” she said.
The current study included ART births in Denmark, Norway, and Sweden from 1997 to 2015, and included 69,751 singleton babies (8,368 born after blastocyst transfer and 61,383 born after a 3-day transfer) and 18,154 twins (1,167 and 16,987, respectively).
The study was presented at the European Society of Human Reproduction and Embryology (ESHRE) annual meeting in Vienna.