Page 623 - Saunders Comprehensive Review For NCLEX-RN

B. Implantation

1. The zygote is propelled toward the uterus and
implants 6 to 8 days after ovulation.
2. The blastocyst secretes chorionic gonadotropin to
ensure that the corpus luteum remains viable and
secretes estrogen and progesterone for the first 2 to 3
months of gestation.

VI. Fetal Development (Box 20-2)

VII. Fetal Environment
A. Amnion
1. Encloses the amniotic cavity
2. Is the inner membrane that forms about the second
week of embryonic development
3. Forms a fluid-filled sac that surrounds the embryo
and later the fetus
B. Chorion
1. Is the outer membrane enclosing the amniotic cavity
2. Becomes vascularized and forms the fetal part of the
placenta

C. Amniotic fluid

1. Consists of 800 to 1200 mL by the end of pregnancy
2. Surrounds, cushions, and protects the fetus and allows
for fetal movement
3. Maintains the body temperature of the fetus
4. Contains fetal urine and is a measure of fetal kidney
function
5. The fetus modifies the amniotic fluid through the
processes of swallowing, urinating, and movement of
fluid through the respiratory tract.

D. Placenta

1. The placenta provides for exchange of nutrients and
waste products between the fetus and mother.
2. The placenta begins to form at implantation; the
structure is complete by week 12.
3. It produces hormones to maintain pregnancy and
assumes full responsibility for the production of these
hormones by the 12th week of gestation.
4. In the third trimester, transfer of maternal
immunoglobulin provides the fetus with passive
immunity to certain diseases for the first few months
after birth.
5. By week 10 to 12, genetic testing can be done via
chorionic villus sampling (CVS).

623