Australian researchers compared 37 babies born through test-tube mixing method, 301 babies born through sperm injection method and 4,000 ordinary babies, taking into account factors such as some women being older when giving birth, the number of children they already had, and the gender of the IVF babies. The results showed that IVF babies had a higher proportion of congenital defects compared to ordinary babies.
The recently published *New England Journal of Medicine* reported that two studies indicated IVF babies were twice as likely to be born with severe physical defects and low birth weight compared to ordinary babies. Nowadays, an increasing number of infertile couples hope to conceive and have their own babies with the help of regenerative medical techniques. This discovery by scientists undoubtedly poured cold water on these infertile couples and drew their great attention. Some people are skeptical about this claim, but their opposition reasons seem insufficient because artificial insemination often results in twins or even multiple births, which carry significant risks.
Scientists do not know what causes IVF babies to be born with congenital defects or low birth weight. Researchers from the Australian research group believe the underlying cause might be infertility or drugs used in IVF experiments, or other factors related to the process of artificial insemination, such as embryo freezing and thawing, which could lead to babies being born with defects.
The research team led by Dr. Schaaf found that implanting the artificially fertilized embryos of infertile couples into another woman's uterus for development did not result in low birth weight at birth, suggesting that low birth weight in IVF babies might be related to infertility rather than IVF technology. Researchers from this group also found that the proportion of low birth weight in twin IVF babies was the same as in naturally conceived twins.
In another study focusing on infant weight, researchers compared 42,463 IVF babies born in the U.S. between 1996 and 1997 with 4.3 million ordinary babies born in 1997. "IVF babies are 2.6 times more likely to be born with low birth weight compared to ordinary babies," said Dr. Laura Schaaf, who led the study at the Centers for Disease Control and Prevention in Atlanta. Low birth weight newborns are likely to cause complications after birth. She added, "Low birth weight babies have a higher mortality rate than ordinary babies, and they may experience long-term developmental issues." Although IVF babies accounted for only 0.6% of children under 10 years old born before 1997, researchers found that among low birth weight babies born during that period, IVF babies made up 7.8%! Dr. Allen Mitchell of the Boston University School of Public Health said that if this new finding is accurate, then single IVF babies might weigh only 94% of normal full-term babies, and non-severely defective twin IVF babies might weigh only 91% of normal babies.
Dr. Mitchell believes that the study results have not proven that the risk of congenital defects or low birth weight in IVF babies is related to female infertility, drug use, or detoxification processes. However, for infertile couples hoping to conceive through regenerative medical techniques, the difference in weight may not be a major concern, and there is no need to worry excessively.
The focus of the two research groups differed; one focused on physical defects in IVF babies at birth, while the other focused on low birth weight. Professor Michelle Hansen of the University of Western Australia, who led the research group focusing on physical defects in IVF babies, introduced: "We found that babies conceived through artificial insemination, a form of assisted reproductive technology, were twice as likely to be diagnosed with severe physical defects within the first year of life compared to naturally conceived babies."
These scientists believe that the fact that even singleton IVF babies who are not premature can be born with low birth weight suggests that their low birth weight may be directly related to infertility treatment methods. However, this is only a possibility, and the cause of low birth weight in IVF babies remains a mystery.