What Could Be Reason For HCG Count Decreased From 35.8k To 32.2k ?

Question : Please advice:
HCG count decreased from 35.8k to 32.2k in 2 days.
USG – EARLY OBSTETRICS (pregnancy)
LMP is 16.02.24; Menstrual age is 6 weeks 1 days
FINDINGSUterus
is anteverted, gravid and bulky in size. There is no uterine / myometrial parenchymal mass lesion
noted. Internal Os is closed.
There is a single small irregular and partially collapsed intra uterine gestational sac is seen with
poor decidual / Trophoblastic reaction.
Mean gestational sac diameter is 23mms corresponding to 7 wks 2 days of gestation.
Gestational sac shows a fetal node / embryo of size / CRL – 5.5mms equivalent to 6 wks 1 day of
gestation sonologically
There is adequate amount of amniotic fluid within the gestational sac.
Yolk sac is identifiable as a small anechoic non-calcifying structure of 3mms in size.
Embryonic cardiac activity is not seen at present possible missed abortion
There is mild subchorionic hemorrhage noted; measuring approx 27 x 12mms in size.
Both ovaries are normal in size and echotexture. There is no adnexal mass lesion noted.
There is no free fluid seen in POD.
Impression – USG findings reveal a single small irregular intrauterine gestational sac with poor
decidual / Trophoblastic reaction and an embryo of 6 wks 1 days gestation sonologically without
cardiac activity (possible missed abortion) and mild subchorionic hemorrhage
Advised - clinical correlation & repeat USG after 1-2 wks for cardiac activity if patient is
asymptomatic for confirmation