thank you for your query.
Sometimes, an early pregnancy
is associated with equivocal BHCG blood results, so a repeat test is required to confirm viability.
A serum progesterone
would not give as much information as the doubling of BHCG would.
If the doctor suspects an ectopic pregnancy ( pregnancy outside the uterus
) also, this would provide the needed information.
Also, for twins, a transvaginal ultrasound
would be more reliable rather than B HCG levels.
Take care, and please go for the appointments as advised.