Side-by-Side: Fetal Development & Abortion
- tangowhiskey
- Dec 12, 2023
- 2 min read
On Abortion
There are a number of different dating systems for pregnancy, the most commonly used being “gestational age” (ga.), which begins from the start of the woman's last menstrual period and dates fertilisation at two weeks along. “Fertilisation age” (fa.) begins on the day of fertilisation, and “implantation age” begins at implantation.
Embryonic Stage
Weeks 3-10 ga. mark the embryonic period, playing an important role in the development of the brain.
At 3-4 weeks fa., a heartbeat can be detected. About 4 weeks fa., the neural tube forms (and with it, brain vesicles form), later to develop into the central nervous system (i.e., the spinal cord and brain). Around 4 weeks ga., the head begins to form, soon followed by distinct facial features. The blood vessel (later to become the heart) begins to pulse, and a heartbeat can be detected later by ultrasound at 6-7 weeks ga.. During week 5 ga., stubs appear that will form arms and legs. It is around this time that most women become aware of their pregnancy (4-7, or more commonly 5-6, weeks ga.).
Around week 7 ga., the embryo begins to develop their first sense – touch. By week 8 ga., fingers have begun to form, the embryo has all of its basic organs (aside from sex organs), and the production of brain cells begins. By 8 weeks ga., ultrasounds reveal the embryo moving, and electrical impulses can be detected (indicating the beginnings of brain function). In week 9 ga., the embryo can suck her thumb, open and close her jaw, stretch, and sigh. By the end of the embryonic stage, cell differentiation is mostly complete. The basic structures of the brain, central nervous system, and peripheral nervous system have been established, and rudimentary neural networks begin to form as neurons form connections with other neural cells.
Most abortions take place during the embryonic stage, and a remaining 20% take place later.
Fetal Stage
The remainder of the pregnancy is termed the “fetal stage.” Systems/structures established in the previous stage continue to develop. Between 9-12 weeks ga., reflexes begin to emerge, and the fetus begins to make motions with its arms and legs. By the end of the third month ga., all parts of the body are formed. This marks the end of the first trimester of pregnancy. During the second trimester, the fetus increases six times in size. The heart grows stronger, body systems develop further, and hair, lashes, and nails form. By the end of the trimester, the central nervous system becomes more responsive, and brain activity resembles that of a sleeping newborn. A baby born at this stage has a slim, but possible, chance of survival. In fact, fetuses born too early have been known to be saveable at as early as 21 weeks ga..
The third and final trimester continues development and growth, and muscles in the lungs prepare for breathing. Childbirth, on average, occurs at 40 weeks ga..





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