The First Trimester of Pregnancy: Baby's Growth
Development of the Fetus During the Early Months of Pregnancy
Sep 29, 2009
The first trimester of pregnancy starts at week 1 and stops at the end of week 12, when the second trimester begins. During this period the baby starts to develop its most essential body parts and functionalities, such as the heart, the neural tube and the digestive system.
The baby is referred to as ‘embryo’ during the first 10 weeks of pregnancy. After that, the baby will be officially considered a fetus. A lot of women prefer calling this new wonder ‘baby’ right from the beginning of the pregnancy, though.
Baby’s Development During the First Five Weeks of Pregnancy
Even though a lot of women may not yet feel that they are pregnant now, a lot happens during the first weeks of pregnancy when the baby starts his journey in the womb. Right after conception, the gender of the baby is determined. The sperm of the father either carries an X-chromosome (a girl) or a Y-chromosome (a boy). The neural tube forms (which will eventually form into the spinal cord and the brain) as well as the heart and the placenta.
Development of the Baby: Week Six to Nine
At this point the pregnancy and baby’s growth is well on its way! The baby’s heart will begin to beat and the digestive and respiratory systems are beginning to form as well. Small buds will appear as well. These will later grow into the baby’s arms and legs. Somewhere around the seventh week of pregnancy, the umbilical cord will have formed. This will serve as a connection between the baby and its mother: it provides oxygen and nourishment and disposes of the baby’s waste.
Feet, fingers, eyes, nose and ears start to appear and the elbows form. The baby really likes bending and flexing, but mothers-to-be will not yet feel their babies movements at this stage of the pregnancy. The head of the baby will grow rapidly during this period and is bigger than the rest of its body. The baby now measures about 16 to 18 millimeters (0.6 to 0.7 inches) and weighs about 3 grams (0.1 ounces).
The Last Weeks of the First Trimester: Week Ten to Twelve
By as fast as week ten of the pregnancy, the baby’s vital organs have all been formed. The head is now about half of the baby’s total length; this is a preparation to keep up with the rapid brain development. The reproductive organs of the baby are also developing rapidly and the genitals of boys and girls even appear to be similar until the end of the eleventh week of the pregnancy. By the end of the first trimester, the baby now measures 61 millimeters (2.5 inches) from crown to rump and weighs about 14 grams (0.5 ounces).
Fetal development starts even before women realize that they are pregnant. The vital organs are formed during the first three months of pregnancy. After twelve weeks of intensive development, the second trimester kicks into place.
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