After writing this article, I realized much of the terminology is unfamiliar to many, so I’m going back and adding more links for the curious to access additional explanation.
It should be no mystery that birth is a miracle. The sequence of events that lead to a successful birth in sexual reproduction is miraculous. That it so frequently fails to work perfectly should be no surprise. That humans expect perfection, even in such a complicated process, is also no surprise; perhaps that is why a number of politicians in this 21st century seem to ignore the frequency of life threatening pregnancies.
Human reproduction is not a matter of birds and bees but of sperm ejaculated into a hormonally prepared and welcoming or unprepared vagina in various ways, from elaborate and beautiful courtships, through mistakes in copulation or faulty contraception, to acts of violent imposition.
Then the miracles begin.
Millions of sperm must vigorously swim an enormous distance relative to their miniscule size to reach the ovum which has matured and been swept into the fallopian tube according to specific time tables where in a matter of days the spermatozoa must have survived in sufficient numbers to alter the outer covering of the ovum and allow one of them to penetrate and fertilize it to combine each of their roughly 23 chromosomes, 22 autosomes and one sex chromosome, ideally, to form a zygote with 46 chromosomes. In about 50% of inseminations a chromosome abnormality prevents further development. About one in 25 zygotes have a genetic abnormality that causes a miscarriage, death, or some degree of disability. The most defective are spontaneously aborted immediately so pregnancy does not occur.
Chromosomes come in pairs; the most common autosomal disorder is Trisomy 21, Down Syndrome, in which there are 3 instead of 2 chromosomes in the 21st pair. Trisomy can also occur in the 18th and 15 pairs. The zygote then has 47 chromosomes. Children with Down Syndrome need special help to develop language. Several medical tests are available to determine the viability of a conceptus.
Sex Chromosomes also come in a pair, males produce sperm which contain either an X or a Y sex chromosome. Females produce ova which contain an X Chromosome. If an ovum is fertilized by a sperm carrying an X, it will have XX chromosomes and be predisposed to become female. If the fertilizing sperm contains a Y chromosome, the zygote will have XY sex chromosomes and be predisposed to become male. It is possible for sperm to have none or multiple sex chromosomes somehow, and the zygote may have XO, XXY, XXX, XYY, XXXY, XXXX, and other combinations. There are 15 possible combinations of sex chromosomes that are viable, able to survive and be born. Describing all their characteristics is irrelevant to this article.
Viable zygotes within 8 days will implant in the wall of the uterus; a placenta will form; and the developing embryo will receive nutrition and eliminate wastes through those blood vessels that connect with the mother’s cardiovascular system. On rare occasions, the sperm reach the end of the fallopian tubes and fertilize the egg before it is swept into the fallopian tube. If the zygote begins to grow in the internal cavity, it cannot embed in the uterus, develop a placenta and grow, resulting in a ectopic pregnancy, which must be terminated to save the life of the mother.
Now the next miracle begins—cell differentiation.
Throughout the first trimester the stem cells of the zygote will be transformed according to genetic programming into brain and nervous system cells, cardiac and other muscle cells, bone cells of the skeleton, stomach, liver, pancreas and other organs, the cardiovascular system, the hematopoietic and lymphatic systems, the digestive, endocrine, and gastrointestinal systems, the urinary tract system, the last to form reproductive system, and, covering it all to protect from the environment, the integumentary system, the skin. The basic parts of every system of the body are formed by the eighth week. The default pattern in genitalia is female. Therefore, all fetuses at 8 weeks appear to be female.
A final miracle then produces the genitalia.
Within weeks androgens, including testosterone cause the brain and genitals to become masculinized. If the mother takes or produces an excess of androgen hormones, even a female XX fetus will become masculinized, affecting both brain and genital development. If the androgen receptors in an XY fetus fail to respond to the androgens/male hormones, male genitalia do not masculinize fully in conditions of partial or complete androgen insensitivity syndrome. Though having XY sex chromosomes, the child may have female genitalia or not fully developed penis and scrotum, depending on the degree of insensitivity to testosterone.
The labeling of the newborn is typically based upon the appearance of the genitalia. Development of the penis depends upon the presence of a tad of genetic material called TDF, testes determining factor, which can attach to an x chromosome in an XX embryo, so sex determination is actually complicated. In the absence of penile looking tissue 3/8 of an inch long, the child is labeled female, even if it has XY chromosomes. If the newborn has penile appearing tissue 1/2 inch long, it is labeled male, even if it has XX chromosomes. If the genitalia are sufficiently ambiguous, not clearly an enlarged clitoris or micropenis, doctors may test for sex chromosomes before labeling the child as a girl or boy. Consequently there are “little girls” who, with the surge of testosterone at puberty have testicles descend and penile growth; some choose to change their identity to male; some prefer to remain female. In the case of complete androgen insensitivity, “little girls” reach young adulthood without having grown breasts or had menstrual periods and are found to have male internal organs and XY sex chromosomes—complete androgen insensitivity.
There is a region in the Dominican Republic where a number of children are born with female genitalia who develop a penis at puberty due to a chromosome disorder that causes lack of an enzyme that activates the chemical changes needed for the prenatal development of the scrotum and penis; at puberty the surge of testosterone causes penis and scrotum grow. It’s quite common, so the community recognizes and deals with it (read about Guevadoces at https://www.bbc.com/news/magazine-34290981).
The effects of prenatal hormones on the parts of the brain involved in sexual identity, sexual expression, and sexual orientation impact the child’s psychological identity, how it is predisposed to express itself sexually, its sexual orientation and sex drive.
Sexual identity, expression and orientation intersect with “race” to exacerbate overt, violent racism, causing the recent increase in harassment and violence toward GLBT BIPOC individuals (Gay, Lesbian, Bi-sexual, Transgender, Black, Indigenous, and other People of Color). At racism conferences we talk about double jeopardy (Black and female) and triple jeopardy (Black, gay, female) as increasing ones chances of being a target for racism.
During the final trimester growth of hair and fine details like fingernails continues.
Institutionalized racism has a devastating impact on pregnancy and birth due to unequal access to health care and insurance and all too often inadequate care for black women. In 2021 the disparity in maternal mortality increased 15% in some studies and even more in south Texas than the rest of the state. There is evidence that doula care improves pregnancy outcomes for black women.
A new 2022 documentary movie, “Aftershock,” shows how the health care is compromised in some cases for pregnant black women and the devastating consequences for the family. It streams on Hulu, etc.