Describe each of the three trimesters of pregnancy.

Question

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Answer 1

Pregnancy is divided into three trimesters, approximately 3 months each, to allow for easier reference to different stages of development. The first trimester is from conception to week12 of fetal development. About the fourth week, the pregnancy test will become positive and early signs of pregnancy begin. The first prenatal visit to a medical facility is ideally around 8 weeks of gestation. At the initial prenatal visits, the pregnant woman is tested for previous exposure to or current infection with several infectious diseases known to have potential deleterious effects on a fetus. By the 5th week of pregnancy, the brain, spinal cord, heart and gastrointestinal tract of the fetus have begun to form. By week 9, all essential organs have started to form. Exposures to environmental hazards, nutritional deficiencies, alcohol, drugs, and infectious diseases have their biggest impact during this trimester. 

The second trimester is from 13 to 27 weeks. Prenatal testing with blood tests and ultrasounds may be performed to rule out some of the more common abnormalities such as neural tube defects (defects that affect the developing spinal cord or brain), Down syndrome and other common problems. If indicated by medical history or abnormal findings, an amniocentesis (collection of amniotic fluid from the gestational sac) or chorionic villus sampling (removing cells from the placenta) may be done to identify genetic or chromosomal disorders in the baby.  Fetal movement is usually felt around week 16-22.  

The third trimester is from 28 weeks through delivery at about 40 weeks. During prenatal visits, blood pressure and urine testing for protein and sugar are monitored to evaluate for the presence of hypertension and gestational diabetes, which can have adverse effects on the developing baby as well as the mother. Full term deliveries occur at 37-42 weeks of pregnancy. Fetal development in the third trimester consists of the final maturation of the organ systems and further growth of the baby in general. Babies born as early as 25 weeks estimated gestational age have well-established potential for viability. As would be expected at this age, the fetal organ systems such as respiratory, cardiac, nervous system and others are not fully developed and put a preterm infant at risk of serious complications. By age 32-34 weeks estimated gestational age, most infants will be born able to breathe on their own but may still have complications related to prematurity.