It is to say that pregnancy with 9-10 month only shows prominent heart sound. So you dont need to worry about.
In humans, the fetal stage commences at the beginning of the ninth week, The fertilisation age or eleventh week gestational age. At the start of the fetal stage, the fetus is typically about 30 millimetres (1.2in) in length fromcrown-rump, and weighs about 8grams.
The head makes up nearly half of the size of the fetus.
Breathing-like movements of the fetus are necessary for the stimulation oflung development, rather than for obtaining oxygen. The heart, hands, feet, brain and other organs are present, but are only at the beginning of development and have minimal operation. The genitalia of the fetus starts to form and placenta becomes fully functional during week 9.