A new study suggests that children born after frozen embryo transfer may be at a greater risk of developing childhood cancer.
The study, published in the PLOS Medicine journal, looked at whether children born after frozen-thawed embryo transfer (FET) are at higher risk of childhood cancer than those who were born after fresh embryo transfer and spontaneous conception.
The procedure of frozen-thawed embryo transfer includes removing eggs from the ovaries, fertilizing them to create embryos, and freezing them. Then, when necessary, the embryo can be thawed and implanted in the patient.
The research included 7,944,248 children born in Denmark, Finland, Norway, and Sweden. Of those, 171,774 children were born after the use of assisted reproduction technology (ART), including FET, and the rest were born after spontaneous conception. Among those born after using ART, 22,630 were born from frozen embryos.
The study found that children born after FET had about 1.6 times higher risk of cancer than those born after fresh embryo transfer and natural conception. However, researchers say data should be interpreted cautiously because the number of children with cancer in the study is small — only 48 cases in the FET group.
Over the past decade, the use of ART more than doubled in the US, with about 2.0% of all infants born every year being conceived using the technology. According to the Centers for Disease Control and Prevention (CDC) data, 330,773 ART cycles performed resulted in 83,946 live-born infants in 2019.
While the evidence on FET's relation to cancer in children needs to be further explored, certain risks are linked to in vitro fertilization (IVF). For example, FET could lead to multiple pregnancy, which can pose a risk to a mother and the unborn babies because twins or triplets are more likely to be premature and have below-normal birth weight.
In addition, recent research published in the peer-reviewed Hypertension journal suggests that using frozen embryos may be associated with a 74% higher risk of hypertensive disorders in pregnancy in comparison to spontaneous conception and pregnancies from fresh embryo transfer.
IVF is used to treat infertility or genetic problems. The treatment can be used if a person who tries to conceive or their partner has conditions like fallopian tube damage or blockage, ovulation disorders, or endometriosis, among others.
John Hopkins Medicine. Freezing Embryos.
American Heart Association. Frozen embryo transfers linked with high blood pressure risks in pregnancy.
Mayo Clinic. In vitro fertilization (IVF).
CDC. ART Success Rates.
University Hospitals Coventry and Warwickshire. CRYOPRESERVATION (EMBRYO, EGG AND SPERM FREEZING).