Twin Pregnancy Detection: Ultrasound Can Confirm as Early as 6–8 Weeks

Transvaginal ultrasound can identify twin gestations as early as 6–8 weeks gestation (4–6 weeks post-conception) by visualizing two distinct gestational sacs (dichorionic) or a single sac with two yolk sacs/fetal poles (monochorionic).

Factors Affecting Detection

• Chorionicity (dichorionic easier earlier).
• Embryo position (one may be hidden behind the other).
• Operator skill and equipment resolution.
• Maternal habitus (obesity reduces transabdominal clarity; TVUS preferred).

Follow-Up

• Chorionicity determination by 10–14 weeks (lambda/twin peak sign).
• Serial growth scans q4 weeks for monochorionic (TTTS, sIUGR surveillance).
• Anatomy survey at 18–22 weeks.

Early diagnosis enables appropriate counseling, monitoring, and referral to MFM if indicated.