normal first trimester
DESCRIPTION
Normal First Trimester. Fetal Biometry Workshop Day 1. Objectives. Describe maternal & fetal early OB Placenta & Fetal Membranes Normal Sonographic Anatomy & Landmarks 1 st Trimester Assessment & dating. Terminology. Conceptual age Gestational age / Menstrual age Trimester - PowerPoint PPT PresentationTRANSCRIPT
Normal First Trimester
Fetal Biometry WorkshopDay 1
Objectives
Describe maternal & fetal early OBPlacenta & Fetal MembranesNormal Sonographic Anatomy & Landmarks1st Trimester Assessment & dating
Terminology
Conceptual ageGestational age / Menstrual age TrimesterEmbryonic phase
Trimesters
1st Trimester is 0-12 weeks2nd Trimester is 13-28weeks3rd Trimester is 28 - 40 weeksPost dates = after due date
Indications 1st TrimesterTo confirm presence of intrauterine pregnancyTo evaluate a suspected ectopic pregnancyTo define cause of vaginal bleedingTo evaluate pelvic painTo estimate gestational [menstrual] ageTo diagnose or evaluate multiple pregnancyTo confirm cardiac activityAs an adjunct to chorionic villus sampling, amniocentesis, embryo transfer, IUCD removalTo evaluate maternal pelvic masses and/or uterine abnormalitiesTo evaluate suspected hydatidiform mole
Patient History TakingPatient ageLMP – normal or notSymptomsPelvic ProceduresReproductive History
GravidityParityG3P1012
Lab Tests
UrineDetects HCG in urine
positive or negative
Urinalysis throughout the pregnancy
BloodMSAFP
Alpha feto protein, serum blood Maternal blood & amniotic fluidProduced by yolk sac, then fetal liverDone 15-22 wks
hCGHuman chorionic gonadotropinPlacental trophoblast cells Blood test most accurate
Early Development
Implantation Sites
Normal Upper corpusFundal region
EctopicFallopian tubes [97%]Uterine cornua [2.5%]]Non-tubal sites
OvariesCervixAbdomen
Early Intrauterine GestationDecidual Reaction Cast
Non-specific finding 3-4 weeksFocal echogenic thickening of deciduaThick endometrium tissue
Early Intrauterine Gestation
Decidual CystNot always visualized2 to 5 mm fluid collectionNo echogenic border Association with or before normal intrauterine gestation
Early Intrauterine Gestation
Implantation BleedMay follow implantation due to erosion of uterine liningHypoechoic cleft in decidua near sac
Intradecidual sign
Gestational sac within the decidua abutting the endometrial canalShould always be seen when maternal serum -hCG is 1700-2000 mIU/mL
Double Decidual Sign
Double-decidual sign
DDS [double decidual sign]
2 concentric hyperechoic rings adjacent to gestational sac
Inner decidua capsularis / smooth chorion
Outer decidua parietalis / developing placenta
Sonolucent center fluid-filled chorionic
cavity
Gestational Sac1st reliable indicator of IUP2 separate fluid filled compartments
Amniotic & chorionicYolk sac & embryoImplants in uterine fundusRounded in shape
MSD + hCG5 mm MSD = hCG of 1800 mU/mlContinue to increase proportionally
MSD
Vitteline DuctYolk stalk, omphalomesenteric ductProvide blood flow to YSFuses at 7-8 weeks Arteries then provide blood flow for foregut, midgut, and hindgut.Vitteline vein drain into the sinus venosus
3 paired vitteline veins
Yolk sac sign
Visualization of the yolk sac within the gestational sacYolk sac often seen when MSD is 5-6 mm and always seen when MSD is 8mm
Yolk SacWithin chorionic sacMSD
10 mm TV20 mm TA42 days or 6 menstrual weeks
MSD & Yolk Sac
Early Intrauterine Gestation
Embryonic Pole1st appearance of fetus~ 45 menstrual daysStraight
echogenic line
Gestational AgeGestational Sac Size
MSD = Length + Width + Height / 3
Yolk Sac SizeSeen in MSD of 10 to 15 mm
Crown-rump lengthEmbryo @ longest length
Predicting Viability
Cardiac activityHeart rate
Bradycardia – 1st trimester demiseLower limits of normal 100 bpm [<6.2 wks]Lower limit of normal 120 bpm [6.3 -7 wks]
Gestational Sac sizeSmall – poor outcome
MSD - CRL mm > 5 mm; if < poor outcomeYolk Sac
Size [large or small] & shape
Embryo at 7 to 9 WeeksEarly umbilical cord
Connecting stalk attaches embryo to developing placenta [chorion frondosum]
Early development of limbs, midgut & CNSLarge rhombencephalic cavity in head
Embryo at 9 to 12 WeeksDeveloping anatomy visualizedExtremities develop>11 weeks bowel returns to abdominal cavity Fetal calvarium well formed [12 weeks]Lateral ventricles contain prominent choroid
Placenta & Membranes
Placental Development
1st Trimester - Placental Growth
Forms from chorionic villi Visible at 7 to 8 weeks’
Structural AbnormalitiesEarliest time abnormality can be detectedEarliest time abnormality should be detected1st trimester:
OmphaloceleDuodenal atresiaOcular defectsCardiac defectsSeptated cystic hygromasBifid appearance – conjoined twins
Growth Evaluation by US
Measurements
GSCRLBPDOFDHCACHC/ACFemur (humerus, ulna, tibia can be done as well but not routine)FL/BPDFL/ACFetal weight estimates (need BPD, AC, and FL)
Guidelines for Dating 1st Pregnancy
5.0 weeks gestational Age Gestational sacNo YS, embryo, or HB
5.5 weeks GA Gestational sac and YSNo embryo, or HB
6.0 weeks GA Gestational sac, YS, very small fetal pole that may be difficult to measure
Gestational Sac
100% specific for no PregnancyMSD grows about 1mm/day up to 10 weeks gestationMeasure inner to innerIf GS > 25mm and No embryoIf GS > 20mm and No YS(L x W x H) / 3 = mean sac diameter (MSD)GA (days) = MSD (mm) +30(TA) MSD of 5mm should = 5 wks GA(TV) MSD of 2-3mm = 4 wks GACan not definitively age a pregnancy on MSD alone
Gestational Sac
CRL measurement
BPD - Biparietal diameter
BPD - Biparietal diameter
OFD – Occipitofrontal Diameter
HC - Head circumference
Same view as BPDLength of outer perimeter of skullUse ellipse or trace
(D1 x D2) x 1.57
Cephalic Index
CI = (shortest axis, BPD/ longest axis, FOD) x 100= 78.3Measure outer to outerNormal mean = 78.3Dolicocephalic <70Brachycephalic >86
BPD and Abdominal Diameter Comparisons
Up to 13 wks head >Abd13-33 wks Head = Abd>33 wks Head < Abd
Femur Length
Measure longest axis of femoral shaftWhere angle of Greater Trochanter is seen>12 weeks can be measured14-22 wks + 1 wk, most accurate timeGrowth rate: 2-3 mm/ wkRemember no bent femurs
FL –Femur Length
AC - Abdominal Circumference
Review – Sequential appearanceMenstrual Week Structure
4 -5 Gestational sac
5 Yolk sac
5.5 – 6 Fetal heart beat
6 Fetal pole
7 Single ventricle
7.5 Spine
7.5 Lower limbs
8 Upper limbs
9 Falx
9 Body movements
9.2 Limb movements
9.5 Midgut herniation
9.5 Choroid plexus
9.5 Hindbrain
12 Fingers
12 Jaw
12.5 Toes
1st Trimester Imaging
Visualization and localization of the gestational sac (intrauterine or ectopic pregnancy)Identification of embryonic demise or living embryonic gestationIdentification of embryos that are still alive but at increased risk for embryonic or fetal demiseDetermination of the number of embryos and the chorionicity and amnionicity in multifetal pregnanciesEstimation of the duration or menstrual age of the pregnancyEarly diagnosis of fetal anomalies, including identification of embryos that are more likely to be abnormal based on secondary criteria (abnormal yolk sac)