Fetal Development

Two weeks: Fertilization The process of a sperm joining an egg. Once one sperm has entered an egg, changes in the egg’s surface prevent more sperm from entering the egg. Once the sperm and egg are joined, the zygote is formed. The zygote travels down the fallopian tube into the uterus.

Three Weeks: Cells have started to specialize which is called differentiation. Implantation: The zygote attaches itself to the uterine wall. The zygote consists of 3 cell layers that will form all body tissue. The placenta is starting to form. The placenta is the organ that attaches the zygote to the mother’s blood supply.

Four weeks: Amniotic sac envelops the embryo. The amniotic sac is a membrane that contains fluid and protects the embryo. The placenta begins to interact with mother’s blood supply This is the point pregnancy tests become much more accurate. This is when the mother will usually miss a period.

Month Two: (5-8 weeks) The neural tube of the embryo forms. This structure will form the brain, spinal cord, and nervous system. Damage to the neural tube during this period can cause birth defects like spinal bifida. The embryo’s heart begins beating. Arm and leg buds form The embryo begins to move

Month Three (9-12 weeks) Embryo develops fingers, toes and a neck. The eyelids fuse shut to protect the eyes as they develop. External genitalia develop. The liver is forming. At the end of this month, the embryo is now a fetus.

Month Four (13-16 weeks) Intestines move into the fetus’ body. Urine is produced by the fetus Important for producing amniotic fluid. Bones are starting to form Hair can be visible on the head. Facial expressions and sucking motions are possible.

Month Five (17-20 weeks) Fetus starts storing fat under the skin. The fetus can hear and be startled by sudden noises. Female fetuses develop uterus and vagina. Fetus’ skin is protected by vernix –a cheese-like covering.

Month Six (21-24 weeks) The fetus can swallow. Fingerprints and footprints form. Rapid eye movement occurs under the fused eyelids. 23 to 24 weeks gestation is the earliest date that premature infants can survive High mortality rate.

Month Seven (25-28 weeks) Hands are fully developed. Lungs begin to produce surfactant – a fluid that allows lungs to expand safely Fetus’ eyelids open again. Being born at 28 weeks has a high survival rate. Survival increases rapidly from this point.

Month Eight (29-32 weeks) Fetal skeleton is fully formed Still soft Testicles descend in male fetuses Some do not descend until after birth – that’s ok. Fetus begins to practice breathing Ms. Rose and her twin was born at 29 weeks 

Month Nine (33-36 weeks) Fetus can detect light Pupils contract and dilate. The fetus is rapidly gaining fat The vernix coating is getting thicker as the skin finishes developing.

Month 10 (37-40 weeks) Fetus develops a strong grasp with fingers. The increasing fat helps the fetus control body temperature after birth. Antibodies cross the placenta to strengthen the fetus’ immune system. Fetus turns head down to prepare for birth.