Straightening your heir: on the constitutionality of regulating the use of preimplantation technologies to select preembryos or modify the genetic profile thereof based on expected sexual orientation.

I. INTRODUCTION

Remarkably rapid advances in genetics and related technology promise to profoundly impact the future of human health and welfare, (1) through applications ranging from the exceptionally practical and obviously beneficial to the exceedingly extravagant and ostensibly superfluous--e.g., from cancer medication safely and efficiently produced in chicken eggs (2) to grow-your-own breast implants. (3) Even those advances with probable potential for future benefit may in the meantime stir controversy regarding public expenditure on their development or regulation of their eventual use. (4) Future applications of genetics in human reproductive technology will almost certainly be no exception. (5)

Prospective parents already routinely screen for certain genetically linked diseases either during or even prior to pregnancy. (6) A few have used the same technology to select the sex of their potential offspring, (7) while others have expressed interest in screening for other non-health-related traits, including sexual orientation, should testing for those traits ever become available. (8) If technology to safely and effectively accomplish germline genetic modification were ever developed, some prospective parents might consider using this technology, as well, to influence the genetic profile of potential offspring. (9)

Although genetic screening or modification with respect to more complex non-health-related traits, including sexual orientation, is currently unavailable and may well remain so for the foreseeable future, contemplation of the mere possibility of such screening has driven much of the current debate about appropriate public policy regarding this ever-developing area of technology. (10) Legislation was proposed in Maine a couple of years ago that would make it illegal for a woman to terminate her pregnancy based on the expected sexual orientation of the fetus. (11) The bill was widely criticized, (12) but did invite speculation that the Supreme Court may one day consider the constitutionality of regulating the use of screening technologies to select for non-health-related traits. (13) Even more recently, a religious figure drew national media attention following his online conjecture that prenatal testing for sexual orientation might eventually be developed and that in utero hormone therapy--though not abortion or genetic modification--pursuant to the results of such testing would be morally justified if tests revealed a genetic predisposition to homosexuality. (14)

Whether reproductive technology and knowledge of the human genome will ever advance sufficiently to allow for selection or modification based on the trait--or, equally importantly, whether society will ever progress sufficiently to render the controversy moot due to absence of the desire to so select--remains speculative. Nonetheless, should the relevant technology become available and used, even if infrequently, regulations of dubious constitutionality will almost surely result.

This note addresses the possible development of preimplantation technologies that would allow for selection of preembryos or modification of the genetic profiles thereof based on expected sexual orientation. Part II explains the relevant technologies, including current use and possibilities for future development, Part III explores some of the consequences of the availability and use of the technologies for this purpose, and Part IV addresses the constitutionality of hypothetical bans on access to these technologies. I conclude that such prohibitions would be unconstitutional, as well as unwise as a matter of public policy.

II. GENETIC SELECTION AND MODIFICATION TECHNOLOGIES

Any current or future possibilities for preimplantation genetic selection or modification depend on the underlying technology of in vitro fertilization (IVF). (15) Millions of children born throughout the world have been conceived through IVF since 1978, (16) and, although expensive, (17) the procedure remains an attractive option for those who would have difficulty conceiving otherwise. (18) Coupled with preimplantation genetic diagnosis (PGD), it affords an opportunity, even for those who could conceive otherwise, to minimize the probability that any resulting children will possess the genes for certain traits, typically severe genetic diseases for which at least one of the prospective genetic parents has a family history. (19) Advanced technology may eventually allow prospective parents to instead maximize the probability that potential offspring will possess certain desired genes for more complex traits. (20)

A. Preimplantation Genetic Diagnosis

Preimplantation genetic diagnosis (PGD), a process designed to investigate the genetic characteristics of a preembryo prior to its transfer into the uterus, (21) has been described as the first technology to "bridge between the effort to 'assist' human reproduction and the ability to intervene in human heredity, thus extending the helping hands of medical science into the innermost workings of early human life." (22) Many prospective parents turn to PGD as a last resort, some after a history of miscarriage or the death of a child from a terminal genetic disorder. (23) Others seek treatment with the knowledge that they themselves suffer from a late-onset genetic disease that they wish to avoid passing on to their offspring. (24) Preimplantation screening offers them an opportunity to avoid the trauma of initiating a "tentative pregnancy" dependant upon the results of prenatal genetic screening (25) and offers still others the opportunity to conceive at all. (26)

Prior to the procedure, the prospective genetic mother undergoes a hormone treatment program (27) to ultimately stimulate the release of approximately ten to twelve ova, (28) which are then surgically removed and fertilized with sperm, usually by injecting single sperm cells directly into each egg. (29) The resulting preembryos incubate for approximately forty-eight hours after the completion of fertilization--or, usually, about sixty hours after the sperm are injected into the ova. (30) Once they are evaluated to determine developmental potential, (31) those preembryos determined suitable continue to incubate (32) until they each comprise approximately six to ten cells. (33)

Preembryos that continue to develop satisfactorily are then subjected to a biopsy to analyze their genetic profile. (34) To capture the necessary genetic material, a small hole is chemically drilled into the zona pellucida, (35) the "rubbery coat" that surrounds the preembryo, (36) and one or two cells are extracted using a microscopic needle passed through the hole. (37) The extracted embryonic cells are dissolved in a solution, (38) and their genetic material is either analyzed to detect chromosomal abnormalities or for sexing using fluorescence in situ hybridization (FISH), (39) or examined to detect the presence or absence of known genetic sequences following the gene amplification technique of polymerase chain reaction (PCR), if single genes are of interest. (40)

After testing, patients select preembryos for implantation based both on their genetic profiles and morphological properties indicative of development potential. (41) If conception is successful, patients have the option of conducting prenatal genetic testing, such as chorionic villus sampling (CVS) or an amniocentesis test, (42) to confirm the accuracy of preimplantation diagnosis, though, perhaps unsurprisingly, many opt not to do so. (43)

B. Enhanced PGD

For now, the effectiveness of PGD is limited, primarily due to the relatively small number of ova involved, the limits of present knowledge of the functions of even those genes that have been identified, and the relatively low chance (typically about ten to twenty percent) that a transferred preembryo will successfully implant and be carried to term. (44) Consequently, the process is currently used primarily to identify chromosomal abnormalities such as an extra chromosome, analyze for one or two specific genetic defects, or determine the sex of the preembryo to screen against gender-linked recessive diseases. (45)

However, potential application of the technology could be greatly expanded to allow for selection of preembryos based on a more complete genetic profile as more is understood about human genetics and the technology itself is improved. (46) Such expanded application would require that all human genes and their functions be identified, techniques for accurately and rapidly screening them developed, and the efficiency with which the necessary genetic information could be recovered from a gene increased "essentially to 100 percent." (47) Additionally, the number of ova harvested from a single woman would need to be increased from the current dozen to at least one hundred, and the success rate for implantation would have to increase substantially. (48) These advances could be realized within the next half-century, though whether technology to accomplish enhanced screening would actually ever be developed and used remains speculative. (49)

C. Germline Genetic Modification