The best and strongest argument in favor of prenatal human rights and against abortion is the simple, indisputable humanity of the unborn. A single-celled zygote, a miraculously growing embryo, a fetus kicking in her mother's womb - all of these are small and dependent people. They are no less human than you or I and no less deserving of loving care and freedom from violence than a newborn, a toddler or a teenager. This is not a religious belief or a personal moral code; it is a combination of inarguable scientific fact, common sense, and respect for the concept of individual human rights that is the basis of every human culture.
If we are to argue compellingly for the rights and lives of the unborn, we need to know as much as we possibly can about them.
Further, life before birth and the way that each of us grew and developed is simply fascinating stuff. Much of the information we need to be effective, educated prolife advocates is rather morbid and depressing; hopefully this section will be an enjoyable read. Just think, every stage of development you're reading about was once your life - isn't that amazing?
All of the measurements of time in this section -- 2 weeks, 3 weeks, etc. -- refer to gestational age, the actual length of time since conception, unless otherwise specified. These measurements could also be referred to as 'post-ovulatory' days or weeks. That seems very simple, but many doctors and other sources of information on prenatal development measure pregnancy in 'weeks gestation' or 'weeks LMP.' The term 'gestation' is particularly confusing, since some sources use it to refer to the age of the prenate (as we do here) and some sources use it to refer to the length of the pregnancy as measured from the beginning of the woman's menstrual cycle. 'Weeks LMP' is a little clearer. Using this method, the woman's pregnancy is measured from the time of her last menstrual period.
The medical community in general seems confused as to what precisely they mean by the term "pregnancy." They define pregnancy as beginning at implantation in some instances; for example, a method of hormone therapy such as Depo Provera that prevents implantation is considered contraception, not abortion. For other purposes, however, pregnancy is measured from the beginning of the menstrual cycle and is considered the condition of the woman's body, having nothing at all to do with the implantation, or even existence, of an embryo.
From a social or political standpoint, the reasons for this confusion is obvious. Defining pregnancy as beginning at implantation dehumanizes the early embryo, and allows for widespread acceptance of birth control methods that would be much more controversial if their true nature were understood. Defining pregnancy as the condition of the woman's body, an alternative to her normal cycles, makes the entire process seem like it is about her and her body alone. Again, the embryo is ignored.
From a practical standpoint, these many different standards make researching prenatal development rather complicated. I have attempted to assure that all data is attributed to the correct gestational age. I have tried to cross-reference my sources -- for example, Geraldine Lux Flanagan's "Beginning Life" attributes facial sensitivity to the embryo at 6 weeks of age. The Association for Pre- and Peri-Natal Psychology and Health sets the onset of tactile sensitivity at 8 weeks. On that basis, I assumed that the APPPAH was using weeks gestation measured from the beginning of the woman's menstrual cycle, and Ms. Flanagan was using weeks gestation to refer to the age of the embryo. If that is the case, their observations coincide. Thus, I subtracted two weeks from all ages mentioned by the APPPAH, converting weeks LMP to weeks gestational age (if you find this confusing, don't worry, you're in good company). Hopefully, this is accurate.