Fetal Development Flashcards
Fetal Proportional Growth
Measures of body length (CRL, lemur length) increase faster than measures of width increase (biparietal diameter, abdominal circumference).
Normal Birth Weight
3200 g (7 lbs)
Low Birth Weight
< 2500 g (5.5 lbs)
Fatal Birth Weight
< 500 g (1.1 lbs)
Small for gestational age (SGA)
< 10th percentile in weight for gestational age, but weight for size is normal
in utero growth retardation (IUGR)
< 10th percentile in weight for gestational age and < 2.5th percentile for abdominal circumference. Mortality is 30 times more likely, mental development may be affected.
Preterm birth
< 37 weeks gestational age. Survival 50% at 24 weeks, 90% at 28 weeks. Skin may appear reddish/wrinkly due to paucity of dermal connective tissue. Primary cause of death is respiratory failure.
Fetal fibronectin (fFN) test
test for preterm delivery risk: vaginal swab for placental adhesive glycoproteins
Respiratory distress syndrome (RDS)
Respiratory distress due to underdeveloped lungs
Respiratory distress syndrome (RDS) prenatal treatment
glucocorticoids to promote surfactant secretion in the lung to prevent collapse.
Respiratory distress syndrome (RDS) POST-natal treatment
continuous positive airway pressure (CPAP) to maintain airway patency.
Lecithin-sphingomyelin ratio
test for RDS risk. Lecithin should rise relative to sphingomyelin beginning in the 34th week, 2:1 = low RDS risk. Amniotic fluid sampled by amniocentesis or vaginal swab.
Amniocentesis
sampling amniotic fluid w/ needle guided by ultrasonography. 14-20 weeks for adequate fluid. Fetal calls for karyotyping, fetal metabolites, proteins, hormones, etc.
Chorionic villus sampling (CVS)
biopsy of chorionic villus w/ needle guided by ultrasonography. 10-14 weeks (after 14 wks, amniocentesis preferred). Slightly higher risk (1-2%), less accurate, earlier karyotyping.
Maternal serum screening
identifying fetal markers in maternal blood. Looking for a-fetoprotein and hCG levels. False positives numerous.
a-fetoprotein
fetal marker in maternal blood that can show neural tube defects, GI defects, Down syndrome
hCG
fetal marker in maternal blood used to test for molar pregnancy, ectopic pregnancy, choriocarcinoma, down syndrome.
Fetoscopy (fetendo)
Encoscopic procedure to visualize the fetus. Invasive, high risk (5-10%), used only in extreme casus
Percutaneous Umbilical Cord Blood Sampling (PUBS)
sampling of umbilical vein blood for genetic or metabolic disoreders (also called cordocentesis). > 17 weeks (cord large enough), same risk as CVS (1-2%)
Culdocentesis
extraction of fluid from the peritoneal cavity within the abdomen. Invasive: must penetrate vagina and peritoneum. Looking for blood; indivative of tubal rupture during ectopic pregnancy.
Dilation and curettage (D and C)
dilation of the cervix and removal of endometrium (scraping or suction). Screens for polyps, cancer, ectopic pregnancy. Placental tissue floats in saline, cancer doesn’t. comparison with hCG levels usually necessary.
Vernix caseosa
waxy or cheese-like white substance found coating the skin of newborn human babies. Starts developing on the baby in the womb around 18 weeks into pregnancy.
Lanugo
very fine, soft, and usually unpigmented, downy hair as can be found on the body of a fetusor newborn baby. It is the first hair to be produced by the fetal hair follicles, and it usually appears on the fetus at about 5 months of gestation.
Amniochorionic membrane (ACM)
Formed by fusion of amnion and chrion. Ruptures prior to birth, ‘water breaking’.