LEC49: Late Fetal Period & Twins Flashcards
fragment of time OBGYNs measure trimesters by
weeks, not months
1st trimester time pd
weeks 1-13
2nd trimester time pd
weeks 14-27
3rd trimester time pd
weeks 28-40
what occurs during 1st trimester
major organ systems form
what occurs during 2nd trimester
fetal growth, differentiation- organ systems develop ability to take on roles, fxns as they should in a born baby
ultrasound fxn
allows to visualize fetus, see anomalies
when is fetus viable
24 weeks from LMP, end of 2nd trimester
when is fetus peri-viable?
23 weeks
may survive
what occurs during 3rd trimester
continued growth, maturation, development of embryo
why is it important to accurate date pregnancy?
many things occur at very specific times during pregnancy so must know accurately how old fetus is
when can visualize fetal heart beat on U/S?
6 weeks from LMP, 4 weeks since conception
what are carnegie stages?
why to visualize embryonic pd of fetal development - til 8 weeks, 10 weeks from LMP
visualize by morpholgy, not just by age
CRL
crown-rump length: measure from crown of head to rump- accurate for dating fetus within 3-5 days
when can use CRL?
7-13 weeks
weeks 9-12 features
1) head = 1/2 CRL of fetus
2) eyes fused
3) ears low
4) see some ossification cts appear in skeleton
when do primary ossification cts appear?
end of 12th week
weeks 13-16 highlights
1) coordinated limb movements
2) ossification of skeleton active
3) scalp hair patterning determined
4) genetalia recognizable
5) eyes anterior
17-20 week highlights
1) mother feels movement
2) skin covered w/ vernix
3) fine lanugo hair present
4) brown fat forms- heat production
5) anatomy US routinely performed
what is vernix
waxy white protection over skin
appears weeks 17-20
why might baby at 24 weeks have trouble w/ heat production
brown fat hasn’t formed
when is uterus at level of umbilicus/bellybutton?
20 weeks since LMP
1 cm from pubic symphysis=1 week
21-24 weeks features
1) skin wrinkled, translucent
2) beginning of surfactant production
3) viability est
26-29 weeks features
1) lungs more developed
2) CNS can control rhythmic breathing, body temp
3) eyelids open at 26 weeks
4) subcutaneous fat
30-34 weeks features
1) skin pink, smooth
2) 32 weeks decreased risk of bleed in brain
3) majority survive
when do eyelids open
26 weeks
when is preterm
< 27 weeks
when is early term
37-38+6 weeks
when is full term
39-40+6 weeks
when is post term
42+ weeks
biggest risk factor for having a preterm birth?
if mom has prior hx of having preterm birth
all risk factors for preterm birth?
1) prior preterm birth
2) uterine anomaly
3) multiple gestation
4) excess amniotic fluid
5) cigarettes/drug use
6) intrauterine infection
how to treat woman who has had prior preterm birth?
progesterone-like injections
diabetes effect on fetal growth?
if mom has diabetes, excess sugar stimulates fetus to create growth factor; can get fetus that’s TOO BIG or too SMALL
what factors might restrict fetal growth?
1) vascular disease
2) hypertension
3) cigarettes
4) genetic disorders
5) anti-phospholipid antibody syndrome
possible post-term issues?
1) increase in mortality
2) dry parchment-like skin, long nails, decreased vernix
3) meconium aspiration
spontaneous incidence of multiple gestations in US?
twins: 1/80
triplets: 1/8,000
why increase in multiple births nationwide?
use of ART, increase in maternal age
what are dizygotic twins
twins from 2 diff eggs; each forms own amnion, chorion
which type of twinning is familiar
dizygotic
percentage of twins that’re dizygotic
2/3 twins
is dizogytic twins maternal or paternal inheritance
maternal
what is monozygotic twins
1 embryo that splits
if 4-8 day split, 1 placenta w/ 2 sacs
if 8-13 day split, 1 sac - risk for fetal death
when do conjoined twins occur
after day 13, monozygotic twins
is monozygotic twins inherited
no
which has better outcome- dizogytic or or monozogytic twins
dizogytic twins
hw might monozygotic twins present
2 separate amnions; 1 placenta w/ 2 diff sacs OR if split before day 4, 2 placentas w/ 2 sacs
day 3-5 twin type
di/di
day 5-8 twin type
mc/di
day 8-13 twin type
mc/ma
day 13+ twin type
conjoined twins
what are monochorionic twins risk for?
1) fetal growth restriction
2) twin-twin transfusion syndrome
3) congenital anomalies
4) miscarriage
5) preterm birth
degree of risk, least to greatest, re: twin type?
dizygotic
di and mono
mono mono
complications of multiple births for baby?
1) preterm brith
2) low birth weight
3) neonatal morbidity and morality
4) congenital anomalies
5) chromosomal abnormalities
6) spontaneous fetal loss
complications of multiple births for mom?
1) gestational diabetes
2) preeclampsia
3) cesarean delivery
4) maternal hemorrhage
5) acute fatty liver
6) placenta previa
when did rate of twins peak in USA
1998
when do singletons deliver
39-40 weeks
when do twins deliver
35-36 weeks
when do triplets deliver
33 weeks
when do quads deliver
30 weeks
what delivers earlier- multiple births or singleton?
multiple births
complications of prematurity
1) hypothermia
2) patent ductus arteriosus
3) intracranial hemorrhage
4) hypoglycemia
5) respiratory abnormalities
6) necrotizing enterocolitis
7) infection
8) retinopathy of prematurity
9) learning disabilities, developmental delays, cerebral palsy
risk of CP in multiple birth?
twins: 5x increased risk
triplets: 17x increased risk
what factors increase perinatal morbidity, mortality?
fetal growth restriction and discordant growth
why do dizygotic twins have great risk of chromosomal anomalies?
each twin has independent risk, whereas monozygotic twins have genetically identical risk
so 2x age related risk for dz twins
what about ART might increase risk of chromosomal abnormalities?
sperm from subfertile men/women may increase risk of chromosomal and gene abnormalities w/ ART
