TRANSVAGINAL DATING ULTRASOUND SCAN (TVS)

What Is the Purpose of a Dating TVS?

• Pinpoint gestational age and expected due date
• Confirm intrauterine pregnancy
• Rule out ectopic or molar pregnancy
• Detect early complications such as blighted ovum or sub-chorionic bleed

How a TVS Differs from an Abdominal Ultrasound

What Is a Transvaginal Dating Ultrasound Scan (TVS)?

Definition and Technology Explained

A TVS dating scan uses a slim high-frequency probe inserted 2–3 inches into the vagina. The probe sends sound waves that create real-time images of your uterus, gestational sac, yolk sac, and embryo on a monitor.

High-Frequency Probe vs External Probe

• High-frequency probe: 5–10 MHz, closer to pelvic organs → sharper images
• External probe: 2–5 MHz, limited resolution before 12 weeks

Types of Transvaginal Dating Ultrasound Scans

• Routine Dating Scan – confirms gestational age
• Fetal Viability Scan – detects heartbeat and growth
• Twin/Multiple Pregnancy Confirmation – counts chorionicity and amnionicity

• Crown-rump length (CRL)
• Gestational sac diameter (GSD)
• Yolk sac presence & size
• Fetal heart rate (FHR)
• Uterine shape & adnexal findings (ovaries, tubes)

• Confirm intrauterine (not ectopic) pregnancy
• Rule out molar or blighted ovum
• Establish accurate EDD for delivery planning
• Assess early viability—heartbeat seen as early as 6 weeks

Ideal gestational age

• 6 weeks 0 days to 9 weeks 6 days is the “sweet spot” for accurate crown-rump length (CRL) measurement.

Who should book immediately

• Women with positive home pregnancy tests wanting early confirmation
• IVF/ICSI pregnancies requiring precise dating
• Anyone with spotting, pain, or previous ectopic pregnancy
• Unsure LMP—irregular periods or recent contraceptive use

Benefits of the Dating TVS Ultrasound Scan

• Earlier detection than abdominal scan—up to 1 week sooner
• High-resolution images 1–2 cm closer to the pregnancy
• Better dating accuracy for IVF—pinpoints transfer day
• Peace of mind for anxious parents

Illnesses Detected Early

• Clothing: Two-piece outfit—easy access but keeps you covered.
• Hygiene: Empty bladder just before scan for comfort.
• Mental comfort: Ask for a chaperone or partner in room if preferred.
• Arrival: Check in 15 minutes early for paperwork.

Pre-requisites Checklist

• Full bladder: NOT needed (empty bladder improves view).
• Consent form: Provided at center; mention allergies or infections.
• Previous reports: Bring HCG blood results if available.

Best Time to Book

Eligibility Criteria

• Singleton or twin pregnancies
• Natural or IVF/ICSI conception
• Symptomatic (spotting/pain) or asymptomatic women
• Age: No upper limit; safe for all reproductive ages

Step-by-Step Procedure

1. Welcome & verification of ID and consent.
2. Position: Lie on exam table with knees bent, feet in stirrups.
3. Probe insertion: Sterile, lubricated probe gently advanced 5–7 cm.
4. Image capture: Sonographer rotates probe to measure CRL, FHR, sac.
5. Reporting: Radiologist reviews images; printed report + digital copy in 30 minutes.

Cautions Before the Test

• Inform staff about active vaginal infections or STI history.
• Defer if heavy bleeding with clots; light spotting is okay.
• Relax: Gentle technique and small probe reduce discomfort.