MedWire News: Study findings suggest that embryo freezing does not increase the risk for adverse perinatal outcomes such as prematurity, low birthweight, and being small for gestational age (SGA) compared with fresh embryo transfers.

“Our study, which is one of the largest on frozen embryo transfer (FET) pregnancies, provides further evidence on the safety of FET,” say Sari Pelkonen (Oulu University Hospital, Finland) and colleagues.

Using data collected from two infertility outpatient clinics, two university hospitals, and the Finnish Medical Birth Register (1995-2006), the researchers evaluated obstetric and perinatal outcomes of children born after FET (n = 2,293), fresh embryo transfer (n = 4,151), and those born after spontaneous pregnancy (n = 31,946).

After adjusting for maternal age, parity, socioeconomic status, and the number of fetuses, women undergoing FET were at significantly less risk for preterm birth (odds ratio [OR] = 0.83) and delivering a child with low birth weight (OR = 0.74) or SGA (OR = 0.63), compared with women who received fresh embryo transfer. Furthermore, mean birthweight was 134 g higher in FET singletons compared with fresh embryo transfer singletons.

However, when FET was compared with spontaneous pregnancy, the team found an increased risk for preterm birth (OR = 1.45) and low birthweight (OR = 1.22), but a decreased risk for SGA (OR = 0.71).

“This information should further promote clinicians to implement elective single embryo transfer combined with cryopreservation in their IVF programs,” conclude the authors.

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