Ultrasound Fetal Growth (Twins)

Yes. Twin pregnancies typically show different growth patterns than singletons: twins often grow more slowly in the second and third trimesters and have lower average birth weights. Discordant growth (commonly defined as >20% weight difference) can signal problems, especially in monochorionic twins. Twins require more frequent ultrasound monitoring and obstetric assessment to track growth and timing of delivery.

Twins can often be seen on ultrasound as early as 5–6 weeks with transvaginal scanning (two gestational sacs or yolk sacs). Heartbeats are usually detectable by 6–7 weeks. By 8–10 weeks both embryos are clearly visible; by 11–13 weeks chorionicity and number are reliably established. In some cases a second twin may be missed until later (vanishing twin or low visibility).

Read a twin ultrasound report by confirming number of fetuses and chorionicity/amnionicity (shared or separate placentas/sacs). Check fetal heart rates, positions, and key biometrics (CRL/BPD, AC, FL) with estimated weights. Note placenta locations, amniotic fluid volumes, cervical length, and any structural findings or discordant growth. Follow recommended follow-up intervals and specialist referrals or additional testing if listed.

Yes — fetal growth restriction is significantly more common in twin pregnancies than singletons. Depending on chorionicity and definitions, roughly 20–50% of twin pregnancies show FGR or one twin small for gestational age; monochorionic twins have higher risk due to shared placental circulation. Because of this, twins undergo closer monitoring with serial ultrasounds and growth assessments.

One twin can be larger due to genetics, unequal placental sharing, or twin-to-twin transfusion in monochorionic pregnancies. Maternal factors—poor nutrition, high blood pressure, smoking, diabetes—or infections can cause intrauterine growth restriction in one twin. Differences in chorionicity/zygosity, umbilical cord problems, or fetal anomalies also affect growth. Regular ultrasound monitoring and obstetric care help manage size discordance.

Many people carrying twins show a larger or earlier bump because the uterus expands more quickly to accommodate two fetuses and extra fluid. However, bump size varies with body shape, muscle tone, prior pregnancies, placenta position and amniotic fluid. Some twin pregnancies look similar to singletons early on. Care providers track fundal height, weight gain and ultrasound growth rather than bump size alone.