Embryology
This single cell is the result of a fertilized ovum and is formed at conception.
What is a zygote?
The round, fluid-filled pouch that appears between 4.5 and 5 weeks, and whose diameter is measured using the mean of its length, height, and width.
What is a gestational sac?
This hormone's levels double every 48-72 hours in early pregnancy.
What is human chorionic gonadotropin (hCG)?
the fluid-filled space behind the fetal neck that is measured between 11 and 14 weeks for first-trimester screening.
What is nuchal translucency?
The decidual layer on the maternal side of the placenta.
What is the decidua basalis?
A solid ball of 16-32 cells, resembling a mulberry, that forms from the division of a fertilized ovum.
What is a morula?
This structure is located within the chorionic cavity, provides nutrients before the placenta forms, and can be seen with an ultrasound by 5 to 5.5 weeks.
What is a yolk sac?
The fluid filled sac that surrounds the fetus
This diagnostic test involves sampling placental tissue, can be performed between 10 and 13 weeks, and is more invasive than a standard ultrasound.
What is chorionic villus sampling (CVS)?
The decidual layer that overlies and surrounds the gestational sac.
What is the decidua capsularis?
A conceptus at this stage enters the uterus around five days and implants seven to nine days after conception.
What is a blastocyst?
This is the most accurate measurement for dating a pregnancy in the first trimester.
What is the Crown-Rump Length (CRL)?
This sign is the appearance of two concentric rings surrounding the gestational sac, and is used to help confirm an intrauterine pregnancy and rule out an ectopic pregnancy.
What is the double decidual sac sign?
A diagnostic test involving sampling amniotic fluid that is performed after 15 weeks.
What is amniocentesis?
The name for the rest of the endometrium lining that is not involved in forming the placenta.
What is the decidua parietalis?
This term describes the developmental stage from implantation to the end of the tenth week.
What is an embryo?
The normal rate of growth for the gestational sac, measured in millimeters per day.
What is 1 mm per day?
The chorionic villi, which form from the trophoblast, secrete this hormone.
What is hCG?
This cystic-appearing structure in the posterior brain, seen between 8 and 11 weeks, represents the developing hindbrain and is a normal finding.
What is the rhombencephalon?
During an early pregnancy ultrasound, this is the average of three dimensions of the gestational sac, which, along with hCG levels, increases until around 10 weeks.
What is the mean sac diameter?
Starting at week 10, the developing human is referred to by this term.
What is a fetus?
A temporary and normal protrusion of the midgut into the umbilical cord that occurs between 8 and 12 weeks.
What is physiologic herniation of the bowel?
The normal heart rate range, measured in beats per minute, for a fetus at nine weeks.
What is 170–180 beats per minute?
The normal range for a fetus's crown-rump length, or CRL, during the 11 to 14 weeks that a nuchal translucency exam is performed.
What is 45–84 mm?