What Happens in the First 6 Weeks of Pregnancy

Fetal Development in the first 6 weeks*

Because of science and technology we now know more than ever about the complex development during the early stages of pregnancy.  Recent research has even shown that a microscopic flash of light occurs when the ovum is fertilized by the sperm.  This unique reaction of zinc in the moment of fertilization has been captured in this video



Fetal Development Week 1

After fertilization, the newly fertilized ovum (zygote) journeys through the fallopian tube to the uterus of the woman.  At the moment of fertilization, the division of cells began and upon reaching the uterus this set of organized cells (blastocyst) begins the process of implantation into the lining of the uterus.  The process from fertilization to implantation can take 5-6 days.  It is reported that nearly 50% of fertilized eggs are lost before a woman’s missed menses (period).

It is important to meet with a Licensed Healthcare Provider to determine how far your partner is in their pregnancy before making pregnancy-related decisions.

Fetal Development Week 1-2

After implantation, the cells continue to divide and form cells that will be specific to the development of organs, the placenta, and more!  By the end of the second week, the embryo creates enough HcG to be detectable with a home pregnancy test.  Because each woman’s body and pregnancy are unique, the detectable level of HcG could vary.  A blood test may help if a urine pregnancy test has not been conclusive.

As HcG levels rise, this triggers progesterone production in the mother’s body and this signals the body to stop the menstrual cycle and maintain the uterine lining which allows pregnancy to continue.

Fetal DevelopmentWeek 2-3

At this point, a woman has liked missed the start of her regular menstrual cycle.  For many, this can be the first indication of pregnancy.  During this time, the embryo has formed three distinct layers of cells: The top layer becomes the skin, nervous system, eyes, and ears.

Brain tissue and heart tissue begin to develop, and fetal cardiac activity begins as early as 18-22 days from the time of conception.  Blood cells begin to develop in the yolk sac and blood cells begin to form a network by the end of the third week.

Fetal Development Week 3-4

The cardiac (heart) tissue is rhythmically beating and newly formed blood cells are circulating through a developing network of blood vessels.  By the 28th day, the developing neural tube has formed the folds that will develop fully into the brain and spinal column.

Fetal Development Week 4-5

Development is happening at a rapid rate.  The arm and legs are beginning to form and all major organs are starting to form: liver, lungs, kidney, stomach, and pancreas.  The unborn baby is now 10,000 times the size it was at conception, about the size of a blueberry!  At this point, the head is growing much faster than the rest of the body the brain must grow at an average rate of 250,000 neurons per minute throughout the pregnancy.3

Fetal Development Week 5-6

So much has happened in this short time!  By the fifth week, the first fetal movements are beginning, and the first sense is developing- touch.  As the baby starts moving it promotes bone and neuromuscular development evidencing newly formed connections between neurons and muscles.  Though the baby’s hair color and eye color were determined at conception, by week 6 the baby’s eye pigment begins to develop.  The baby is now growing at approximately 1mm per day.  At this point, if the pregnancy is ectopic (developing outside of the uterus, typically in the fallopian tube) signs and symptoms begin to appear.  Though rare, it is important to seek early pregnancy detection to rule this out, especially if the woman has any history of prior ectopic pregnancy.