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Unique from Day One


by David Prentice and Tara Sander Lee

Scientific discoveries have revealed the incredible way human life begins and develops

<i>Getty Images/iStock/Zffoto</i>

Today we face unprecedented challenges to the respect due to each human life, from his or her very beginning. But there is also unprecedented scientific evidence that life begins at Day One. The dynamics of human fertilization were discovered in the 19th century, and advancements in genetics and embryology have confirmed that life does begin at conception.

Leading embryologists Ronan O’Rahilly and Fabiola Müller, for example, have noted that while life is a continuous process, fertilization is “a critical landmark” at which “a new, genetically distinct human organism is formed” (2000).

Below is a brief outline of what science tells us about when life begins and the remarkable process of human development.

• Conception, or fertilization, is the union of a human egg and sperm, resulting in a zygote. Though sometimes called a “fertilized egg,” it is no longer an egg, but a single-cell human embryo. This is how every person’s life begins.

• Central to multiple factors that work together to bring about life is deoxyribonucleic acid (DNA) — unique genetic material present in every living organism. The DNA molecule replicates (copies itself ), a critical step necessary for human growth and development. At fertilization, one copy of DNA from the father combines with a copy of DNA from the mother to form the genome of the new single-cell embryo, with its own characteristics.

• After fertilization, the zygote (one-cell embryo) begins to undergo cleavage (cell divisions) and grow from a single cell to a 2-cell stage, to a 4-cell stage, then an 8-cell stage, and finally a 16-cell stage called a morula.

• This developing embryo continues to grow and move through the fallopian tube to the uterus, forming the early blastocyst at 5-6 days after fertilization. At 6-7 days after fertilization, the developing human has formed a specialized outer layer called the trophoblast, which allows the embryo to implant into the endometrium (the lining of the womb).

• The developing human organism is called an embryo from the time of fertilization until the end of the eighth week of gestation, when it is then called a fetus. These definitional terms and time frames have been recognized by leading scientists and scientific organizations for decades. The term “pregnancy” is sometimes defined as beginning with the implantation of an embryo into the uterine wall. But the biological fact remains that fertilization, not implantation, is the “critical landmark” when a unique human life begins.

• Approximately three weeks after fertilization, the developing heart begins to beat with the preborn child’s own blood. Brainwaves can be detected a few weeks later, as early as Day 45. Within 8-10 weeks after conception, every organ is present, and the baby already has unique fingerprints.

• We are now able to treat the fetus in utero thanks to advancements in medical diagnosis and therapy. This is the exciting “Perinatal Revolution” of treating the “patient within the patient.” Advances in perinatal medicine have cured children from disease before birth and resulted in increased survival rates for premature babies. Novel innovations in screening and genetic diagnosis, as well as future prospects in cell-based therapies, tissue engineering, gene therapy and artificial wombs (for the extremely premature) are significantly expanding the field.

In these and many other ways, science continues to demonstrate the awesomeness of every life from the moment of conception. The Oxford Dictionary defines life as: “the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change.” So, when does life begin? Science speaks for itself. From the earliest cell stage on Day One, the human organism has everything it needs to grow, multiply, function and continually change. This is the miracle of life. This is the miracle of being human.

DAVID A. PRENTICE, PH.D., an internationally known expert on bioethics, is vice president and research director for the Charlotte Lozier Institute. TARA SANDER LEE, PH.D., a scientist with 20 years’ experience in academic and clinical medicine, is an associate scholar with CLI.