The way in which embryos are prepared during in vitro fertilization may influence the size of the baby that's born, a new study from Finland suggests.
Embryos that spend long periods growing in culture (around five to six days) before being transferred to the mother’s womb are more likely to be born heavier than normal for their gestational age, compared to embryos that spend a shorter period in culture (two to three days), the study found. (Gestational age refers to how far along a pregnancy is.)
On the flip side, embryos that spend long periods in culture are less likely to be born small for their gestational age, the researchers said.
Previous studies have shown babies born as a result of IVF treatment are at an increased risk for preterm birth and low birth weight. Factors related to the pregnancy, or to the IVF technique itself, may be responsible for the association. Few studies have looked at the effect of culture time on the baby's birth weight, however.
Still, additional, larger studies are needed to confirm the new findings, the researchers said.
In the study, researchers at the University of Helsinki analyzed information from 1,079 singleton babies (not twins) who were born after their mothers had undergone IVF.