In Vitro Fertilization and Embryo Transfer (IVF-ET): Issues on the Wake of the US Supreme Court Decision on Abortion

Since the Supreme Court of the United States (SCOTUS) handed down its decision on the Dobbs versus Jackson Women’s Health Organization abortion case, we have discussed contraceptives as possibly a future target for further laws against reproductive rights. But even more vulnerable than contraception in the wake of the Dobbs decision are certain fertility treatments, notably in vitro fertilization and embryo transfer (IVF-ET)

The recent SCOTUS Dobbs v Jackson Women’s Health Organization decision regards a Mississippi law prohibiting abortions after 15 weeks gestation. The majority decision ended up, not only upholding the Mississippi law, called the “Gestational Age Act,” but also overturning the Roe V Wade decision of 1973. Of the nine justices on the Court, six justices voted to uphold the Gestational Age Act, while five of those six also voted to overturn Roe v Wade. Chief Justice John Roberts issued an opinion in favor of upholding the Mississippi law but not overturning Roe v Wade, while Associate Justices Stephen Breyer (now retired), Sonia Sotomayor, Elena Kagan issued a minority opinion against the Mississippi law and in defense of Roe v Wade. The majority opinion, overturning Roe, was authored by Associate Justice Samuel Alito, who, along with Associate Brett Michael Kavanaugh, wrote that the reasoning applied to abortion would not be applied to any other issues, such as contraception, but Associate Justice Clarence Thomas did indeed suggest that future cases may reconsider contraception as a privacy right.

But fertility treatment does not fall within the realm of contraception. It’s the opposite of contraception, so why are we discussing fertility treatment, specifically IVF-ET, in today’s post? The reason is because rhetoric by anti-abortion activists and anti-abortion politicians has always expressed a distaste for this reproductive technology, because it produces human embryos, many of which are destroyed, or otherwise never will develop into newborn babies. So there have been discussions in public about the prospect of the Dobbs decision clearing a pathway for laws against IVF-ET.

To discuss what IVF-ET is, we need to discuss a little about the process of early human development leading to the natural initiation of pregnancy. Each sex produces special cells called gametes. An ovum, or egg, is a female gamete, much larger than a sperm cell, a male gamete. Gametes differ from your other body cells, because the gametes have only one copy of each chromosome (they are haploid), whereas other body cells have pairs of chromosomes (the cells are diploid). Thus, while each cell in your heart or liver contains 46 chromosomes, each of your gametes contains just 23 chromosomes. Each month, a woman releases usually just one ovum from one of her two ovaries, but sperm cells from the man are numerous. The ovum travels from the ovary through the fallopian tube on its way to the uterus. If the timing is right, and if other conditions are right, while moving through the fallopian tube, the ovum will meet up with about 200 sperm cells, a tiny fraction (1/10,000) of the 2 million or so sperm cells that typically enter the cervix. The sperm cells work on the membrane surrounding the ovum and the process leads to the haploid genome of one sperm cell entering the ovum and combining with the ovum’s haploid genome. This leads to a zygote, a fertilized ovum with a diploid genome, meaning 46 chromosomes. The zygote divides into two cells and over the course of a few days, more cell division leads to a four cell stage, and eight cell stage, and when there are sixteen or more cells the entity is called a morula. Cell division continues, transforming the morula into a blastula, a kind of hollow ball of cells. When the various cells of the blastula have begun to differ from one another, the blastula has become a blastocyst, consisting of about 100-150 cells. While all of this is happening, the growing mass of cells keeps moving through the fallopian tube and into the uterus. The blastocyst stage is reached around five to six days after fertilization, by which time it has reached the uterus and the lining of the uterus, the endometrium, has changed in a way that makes it ripe for a blastocyst to implant into it. Implantation of a blastocyst into the endometrium is where pregnancy begins.

Now, there are many things that can go wrong with this process. In fact, usually it does not work. In nature, most fertilized ova never make it to the implantation stage and that’s in a woman in whom everything is working right. In women whose fallopian tubes are narrow, due to previous pelvic inflammatory disease, the developing ball of cells can get stuck, or move too slowly as it keeps growing. This can lead to implantation in the tube, a tubal pregnancy, the most common type of ectopic pregnancy, which cannot ever produce a baby and puts the woman’s life in danger if it does not end.

IVF is a treatment offered to couples who have not been able to achieve a successful pregnancy naturally, or with other fertility treatments. A woman who opts for IVF will take hormonal treatment to stimulate the production of eggs, not just one per month, but multiple ova. Ova are then extracted directly from her ovary and fertilized with sperm from the aspiring father in a laboratory setting. Fertilized eggs, zygotes, as then observed under the microscope over the next few days to see how well they progress through the two-cell, four-cell, eight cell stages, or all the way to the blastocyst stage, depending on a variety of factors. If there is a shortage of healthy embryos, such as only a couple, the fertility specialist may opt to implant them around day three, when they are in the realm of four to eight cells. If there are more healthy-looking embryos, the specialist might want to wait until day five, or all the way to the blastocyst, stage to see which ones do better than others and then select the better ones to implant. Embryo transfer (ET) is the process of taking one or more such embryos and injecting them through a special tube, through the aspiring mother’s cervix, to optimal spots within the uterus, using ultrasound guidance.

The more embryos that can be injected, the more likely the treatment is to succeed and the less likely the couple will have to go through more cycles of IVF attempts. However, transferring more embryos in one sitting increases the chances of a twin pregnancy, or higher multiple pregnancy. If too many embryos (which for most women could mean more than one) implant successfully, doctors can perform a reduction procedure in which the less optimally located ones are removed. Anti-abortion activists and anti-abortion politicians don’t like this, because the removed embryos die, nor do they like the fact that often embryos are preserved a low temperature —a process called vitrification— and kept for years or decades, usually never being implanted into a mother. It may be possible to adjust to some laws that may emerge restricting IVF, adjust by limiting the number of embryos transferred, but then the success rate will decrease, and the cost of the process, which is substantial (most couples cannot afford IVF in the first place), will rise. IVF-ET is a messy process in which zygotes, morulae, and blastocysts die. But then, so is the natural process that initiates pregnancy.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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