A fetus (plural form fetuses) is the name for an embryo after 8 weeks of development. During human pregnancy, 9 months in the womb of a mother are necessary for full fetal development. During those 9 months, the fetus develops all major organs, body systems and an entire skeleton.
In the earliest stages of development, the fertilized egg is referred to as an embryo. At about eight weeks, when the embryo begins to resemble a newborn more clearly, it enters what is called the fetal period. It is then called a fetus until it is born. The fetal period is a stage that produces increased growth and full development of the organs.
Sometimes, fetal problems cause birth prematurely. Human fetuses usually cannot live outside the womb before about 20 weeks, so if the fetus is expelled from the womb before it can survive outside, the incident is called either a miscarriage or an abortion. After about five months, if the fetus is born dead the birth is called a stillbirth, and if the fetus is alive it is called a premature birth.
Once fertilization of the egg takes place, the egg becomes implanted into the wall of the uterus, through a process called implantation. The embryonic disc begins to form in the uterus. This embryonic disc will create three layers from which the fetus will develop. The first layer is the ectoderm. In this layer, the nervous system and sense organs will form. Next, we have the mesoderm, which creates a number of body systems, including the circulatory, muscular, and skeletal systems. Last of the three layers is the endoderm, which forms digestive and various gland systems. The placenta is just beginning to form along the uterus walls. This will not only supply the fetus with nourishment and food, but also transfer waste products out. A small heart begins to pump blood through blood vessels. The kidneys, lungs, liver, nervous system and intestines all begin to slowly develop. At the end of month 1, the embryo is about one-fourth an inch long.
The second month of pregnancy is one of very rapid growth for the baby. During this month, all body systems and organs will grow. The bone cells along with stomach, brain, liver, lungs, and sex organs all develop in the second month. Eyelids form but are fused shut until later in pregnancy. Arms, legs, fingers and toes form, so that by the end of the second month of pregnancy, the fetus looks actually looks like a human infant. Rather than being called an embryo, the baby is now called a fetus, and ultrasounds offer a look at the developing fetus. The fetus is about one and a half inches long at the close of the second month.
Arms, legs, hands, feet, fingers and toes are all fully developed by the third month of pregnancy. Fingernails appear and facial features are recognizable. The fetus’ eyes are almost finished forming.  For the first time in his or her life, the fetus is now able to move and wiggle, but because the fetus is still so small, the mother will not feel the child move for about another month.  The sense of taste is developed, although the baby does not eat anything through his or her mouth just yet. The umbilical chord will continue to bring food to the fetus throughout the entire pregnancy. At the end of the third month, the fetus has grown to be around 3 inches long. 
The rubbery cartilage that composed the fetus’ skeleton is now turning into hard bone.  The baby is now large enough that when it kicks or moves around in the womb, the mother will most likely feel it. Blood vessels are becoming visible through the fetus’ skin. Hair is starting to appear on the baby’s scalp, and eyebrows and eyelashes are present. Soft hair called lanugo covers the body and head of the fetus. This fuzz will disappear before birth.  Reflexes such as chewing, sucking, and swallowing are developing. The baby may begin his or her habit of sucking its thumb during this month. The fetus is around 6 inches at the end of the fourth month of pregnancy. 
Over half-way through pregnancy, the fetus is 7 or 8 inches long at the fifth month. The fetus’ skin is now covered with vernix caseosa, which is a white, slimy fluid that protects the baby against the acidic amniotic fluid. His or her ears are developed enough so that he or she can hear the mother’s voice and heartbeat. The baby is following regular sleep patterns. Interestingly enough, sweat glands are formed and they function while still in the womb, even though the baby is surrounded by amniotic fluid. There are an increasing number of nerve cells developing in the front of the fetus’ brain. The baby’s movements will continually grow stronger and more noticeable as muscles and bones develop. 
The sixth month begins with the miracle of sight, when the fetus’ eyelids open and reveal it’s perfectly formed eyes for the first time. Vocal chords are now developed enough to scream and cry, although they will not function until the baby is born and is out in the open world. The fetus will practice swallowing, which can sometimes result in hiccups. Now over twelve inches long, the fetus is growing rapidly and weighs in at around two pounds. 
From the end of the sixth month and on, the fetus is developed enough that he or she would survive an early birth. This is called premature birth, and special care in a hospital is necessary for the baby to survive. Still in the womb, the fetus’ body fat is increasing rapidly, in preparation for birth. Bones will have fully developed by the end of the seventh month. His or her eyes will have 20/400 vision, which means that only things within a few inches of his or her face will be recognizable. At this point of formation, the fetus is 14 to 16 inches long and weighs around three pounds. 
Eighth and Ninth
The last two months of fetal development are not as crucial to life at the earlier months. During these months, the fetus will continue to gain fat all over his or her body, which smooths out wrinkled skin and rounds out the body. The reddish shade that previously tinted the skin now fades, and the color pigment changes to whatever skin color follows the race of the fetus. Both heart rate and organ activity increases. Digestive organs, which were inactive before this point in pregnancy, expel waste. This waste will remain in the fetus until after birth, when parents find it in the first dirty diaper. Lanugo that once covered the fetus’ entire body will disappear. The baby will position itself upside down, with his or her head pointing towards the cervix, the ideal position for birth. If the fetus does not do so, and is positioned bottom down, the birth is called breech, and comes with complications involving both the baby and the mother. The average baby size at birth is 7 pounds and 19 inches long.
- Main Article: Abortion
Unborn fetuses are distinct and whole human persons. When a sperm and egg cell unite in the process of fertilization, both cease to exist, and the resulting embryo has a unique genetic structure. Thus, the embryo is distinct from either parent. Furthermore, they have the innate capacity to complete their development. On the basis that humans have value and that it is morally wrong to kill a human without a valid justification, the killing of a fetus is murder. Fetuses differ from persons outside of the womb in their size, level of development, environment, and degree of dependency. None of these qualities change the fact that fetuses are human and have inherent value. Children are smaller and less developed than adults, but it is still wrong to kill them. The same logic applies to abortion. Likewise, location and dependency do not change what the fetus is.
Before Rebekah gave birth to the twins Jacob and Esau, "the children struggled together within her" (Genesis 25:22). When the Virgin Mary found she was pregnant with Jesus she visited her cousin Elizabeth, who was also pregnant with the child who would later be known as John the Baptist. When Elizabeth heard Mary’s greeting, "the babe leaped in her womb" (Luke 1:41). Elizabeth said to Mary, "as soon as the voice of thy salutation sounded in mine ears, the babe leaped in my womb for joy" (Luke 1: 44).
The Bible therefore shows that the human fetus in the mother’s womb is already a true human being, able to react and express emotions. Embryonic and fetal photography from Lennart Nilsson and others clearly show the humanness of the fetus. Deliberate abortion, therefore, is taking a human life.
In their book The Bible Has the Answer, Dr. Henry Morris and Martin E. Clark say, "In view of these facts, the current sudden increase in legalized abortion practice is very disturbing." They add that despite what governments or medical or legal professionals do to legalize abortions, it is clear that deliberate abortion is murder in the sight of God.
- Fetal Development: Month 1 Author Unknown, Baby 2 See, 2009.
- Approximate Timetable of Prenatal Development Dr. Robert Myers, Child Development Institute, 2009.
- Fetal Development: Month 2 Author Unknown, Baby 2 See, 2009.
- Fetal Development: Week 10 Author Unknown, Baby 2 See, 2009.
- Fetal Development Author Unknown, Baby Center, 2009.
- Klusendorf, Scott. The Case for Life: Equipping Christians to Engage the Culture. Wheaton, IL: Crossway, 2009. Print.
- Fetal Development: Second Trimester. Pregnancy Resource Center of Snohomish County.
- Fetal Development Author Unknown, Sutton Health, 2009.
- From Conception to Birth Author Unknown, Mead Johnson Nutrition, 2009.
- Fetal Development on Pregnancy.org
- Stages of Pregnancy and Fetal Development by Lydia Warner and Alexa Rosenberg