Welcome to HCM.
Your wife's USG scan reveals CRL 8.9mm with positive heart beat. So probably gestational age
is around 7wks.
Twin pregnancy can be early detected around 5-6wks as like singleton pregnancy and detailed feto-placental profile can be obtained around 8wks.
Status and detail of twin pregnancy in early wk can be obtained more reliably with TVS (Trans vaginal sonography
) over TAS (Trans abdominal sonography).
To assess growth and development of both twins,you have to do periodical USG scan with consultation of your doctor.
Avoid heavy work,take protein rich diet, folic acid
& calcium supplements
.Also need proper sleep.