A Closer Look at Fetal Development in First Trimester

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Here come the First Few Months of Pregnancy!

Congratulations!  Your pregnancy test finally turned positive and you are eagerly anticipating the next months of your pregnancy.  At this moment, baby is only a tiny ball of cells that has implanted in the uterine wall, but over the course of the next nine months, will develop into a fully functioning baby.

First Month

The first month of pregnancy starts from the day of your last period, before you are actually even pregnant.  So by the time you miss your period and discover that you are pregnant, you are already four weeks along.  Once ovulation occurs, somewhere around week two, the egg must be fertilized by a sperm cell within about 24 hours.  The resulting embryo will contain half of its genes from mom and the other half from dad.  After fertilization, the embryo will travel down the fallopian tube and implant into the uterine wall around six to twelve days after ovulation.

Shortly after implantation, the pregnancy will begin producing hCG, the hormone of pregnancy.  It’s around this time that a urine pregnancy test will turn positive.

Second Month

By the beginning of the second month of pregnancy, the embryo will begin developing rapidly.  Initially, the embryo has three layers of tissue ““ the ectoderm, mesoderm and endoderm.  Each layer will eventually give rise to a series of organs that make up the baby’s internal anatomy.  The outside layer, or ectoderm, will become the baby’s skin, eyes, ears and nervous system.  The middle layer, or mesoderm, will become the cardiovascular system, bones and muscles, and reproductive system.  The internal layer of cells, or endoderm, will become the lungs, intestinal tract and bladder.

Primitive structures, like the nose, arm and leg buds, eyes, ears and lips are being formed and develop into the form that we are familiar with.  In addition, baby’s body begins to straighten out of the curve that she’s been in up to this point.

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