First Trimester Ultrasound Walter P Trymbulak MD, Ph.D. Saint Francis Medical Group Division of Obstetrics and Gynecology Saint Francis Hospital and Medical Center

Objectives • Define the first trimester of pregnancy. • Review the role of ultrasound imaging in the first trimester of pregnancy. • Discuss the ways in which ultrasound can assist us with management of first trimester pregnancy problems: • First Trimester Bleeding – Pregnancy of Unknown Location – Threatened Abortion » Subchorial Hemorrhage – Spontaneous Abortion

The long and winding road…

Embryo

The First Trimester • The 12 weeks that starts on the first day of the last menstrual period. – Fertilization – Implantation – Organogenesis

• Critical time in development: almost all complete by the end of the 10th week.

Components of a First Trimester Scan Uterus Ovaries Gestational Sac Yolk Sac Amnion Fetus Fetal Heart Rate Cul-de-Sac

Uterus • Uterus – – – –

Cervix Internal Os Endometrium Abnormalities – Fibroids, Mullerian Anomalies

Uterus

Cervix

Internal Os

Uterus

Ovaries

Gestational Sac • Gestational Sac – – – –

Size Location Number Subchorial echolucencies

Gestational Sac

Gestational Sac

Gestational Sac

Gestational Sac

Yolk Sac • Yolk Sac  

Size Location

Yolk Sac

Fetal Pole • Fetal Pole – Crown Rump Length – Obvious anomalies

Fetal Pole

Crown Rump Length

Fetal Pole

Fetal Heart Rate

Cul-de-Sac

Cul-de-Sac

Clinical Perspective • The problems we manage early in pregnancy. “I’m spotting” “I’ve got pain” “Am I having another miscarriage?” “Could this be a tubal pregnancy?”

Differential Diagnosis of First Trimester Bleeding • Threatened abortion • Spontaneous abortion • Ectopic pregnancy • Molar pregnancy • Non-obstetrical bleeding – Trauma – Cervical polyp – Cancer

Threatened Abortion • Clinical term referring to bleeding prior to 20 weeks with a closed cervical os • Complicates approximately 25% of first trimester pregnancies (clinical pregnancies). • Common reason for first trimester ultrasound

Pregnancy Loss Rates

Components of a First Trimester Scan Uterus Ovaries Gestational Sac Yolk Sac Amnion Fetus Fetal Heart Rate Cul-de-Sac

Evaluation of First Trimester Bleeding Uterus Ovaries Gestational Sac Yolk Sac Amnion Fetus Fetal Heart Rate Cul-de-Sac

Systematic Approach to First Trimester Ultrasound 1. Identify the Location of the Pregnancy 2. Confirm the Viability of the Pregnancy 3. Assess the Viable, Intrauterine Pregnancy for Physical and/or Chromosomal Normalcy

Identify the Location of the Pregnancy • What Should I See and Where Should it Be? • Should I see a sac? • Should I see a pole? • Should I see a heartbeat? – What is the Gestational Age based on Last Menstrual Period? – Serum Level of HCG and When was it drawn?

MENSTRUAL AGE IN WEEKS (Weeks )

4

5

Gestational Sac

I---------I

Yolk Sac Fetal Pole and Heart

6

I---------I I---------------I

7

Laboratory Test for Early pregnancy • Discriminatory Zone HCG and Sonography  HCG Level that reliably identifies intrauterine gestations 1,000- 2,000 for TVUS >2,500 for Transabdominal US

 HCG Levels above “THE ZONE” with absence of IUP on TVUS strongly suggests ectopic or early pregnancy failure

Laboratory Test for Early pregnancy

XXXXX XXXXX • Discriminatory Zone HCG and Sonography  HCG Level that reliably identifies intrauterine gestations 1,000- 2,000 for TVUS >2,500 for Transabdominal US

 HCG Levels above “THE ZONE” with absence of IUP on TVUS strongly suggests ectopic or early pregnancy failure

Discriminatory Zone HCG and Sonography

Discriminatory Zone HCG and Sonography

Expected Location

Expected Location

Abnormal Pregnancy Location

Pregnancy in the Wrong Location • Ectopic Pregnancy – A pregnancy in which the developing blastocyst implants somewhere other than the endometrium of the uterine cavity.

Ultrasound Diagnosis of Ectopic Pregnancy • The Ultrasound should document – The absence of the pregnancy in the uterus – The location of the pregnancy if seen – The size of the ectopic/tubal mass

– The presence or absence of cardiac activity. – The presence or absence of free fluid in the culde-sac.

Empty Endometrial Cavity

Free Fluid in Cul-de-sac

Pregnancy in the Wrong Location • Ectopic Pregnancy – A pregnancy in which the developing blastocyst implants somewhere other than the endometrium of the uterine cavity. – Manage as the clinical situation dictates with either Medical or Surgical protocols.

Empty Endometrial Cavity

Pregnancy of Unknown Location • An empty endometrial cavity, with no evidence of an intrauterine gestational sac or retained products of conception and no visualized extra-uterine pregnancy or sign of ectopic pregnancy. • Manage with a tincture of time, repeat laboratory testing and repeat ultrasound

Confirm the Viability of the Pregnancy • Do I see the expected structures? • Are they “normal” in structure, size and rate?

• If I see the expected structures are there any that suggest that the pregnancy may end in a miscarriage?

Expected Structures and Rates

Expected Structures Absent

Molar Pregnancy

Confirm the Viability of the Pregnancy • Do I see the expected structures? • Are they “normal” in structure, size and rate?

• If I see the expected structures are there any that suggest that the pregnancy may end in a miscarriage?

Gestational Sac • First sonographic sign of a pregnancy • Usually visible at 4.5 - 5 weeks gestation • Small, fluid-filled, eccentrically located • Cursors placed on sac itself • Does not include echogenic region surrounding sac • If no distinct structures visible inside, dating based on mean sac diameter (MSD)

Gestational Sac

Gestational Sac • The “mean sac diameter” is the key for evaluation of early development • Location should be noted but is not diagnostic of missed abortion • An irregular or partially collapsed sac is not diagnostic of missed abortion • A yolk sac must be seen by 20 mm and a fetus with cardiac activity by 25mm

Gestational Sac

Gestational Sac Criteria for Missed Abortion

Empty Amnion • Difficult to always distinguish from a large yolk sac • Yolk sac should also be present to make this diagnosis • Predictive of pregnancy failure

Empty Amnion

Yolk Sac • First anatomic structure within the GS • Confirmation of IUP • Spherical with sonolucent center

• Noted in beginning of 5th week of gestation

Yolk Sac • Nutrients to embryo via Vitteline Circulation • Obliterated by 7th week in 98% of embryos • Is NOT in Amnionic cavity • Resides in Chorionic cavity

• Max. diameter approx. 6 mm by 10 weeks

Yolk Sac • This is an extraembyonic structure • Very large (>9mm) and very small(