Monday morning, PST: time for some science with a side of controversy, Danio-style
There’s a Department of Health and Human Services document circulating that’s got the pro-choice lobby up in arms. Afarensis and The Questionable Authority weighed in on the sociopolitical impact of such a policy last week, but in addition to the significant threat to reproductive rights that it presents, this proposal is yet another example of the complete lack of scientific expertise informing decisions about public health.
At issue is the determination of a time point that marks the beginning of pregnancy. The consensus of the medical community is that an established pregnancy occurs at the point when the blastocyst successfully implants into the uterine wall. This time point makes a lot of sense in considering early events in the reproductive process. Pre-implantation embryos have a vast distance to travel, complex chemical cues to navigate, and a ticking biological clock to contend with within the bounds of the female reproductive cycle. Roughly 40% of all embryos don’t survive the ordeal. These odds are one good reason to hold off on crying ‘pregnant’ until a successful implantation is achieved; another is that implantation signifies the beginning of the physiological impact of a pregnancy on a woman’s body. Developmental events prior to implantation have essentially no impact on maternal tissues, which are just marking time until the beginning of the next menstrual cycle. The massive signaling between embryonic and uterine tissues that occur during implantation, the establishment of maternal and embryonic connections and boundaries, delineating the difference between ‘self’ and ‘not self’, are all medically relevant occurrences in terms of the physiology of the female patient, hence the general accord within the medical community in marking this time point, and none before it, as the point at which a pregnancy is established.
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