I personally would try for a vaginal birth. It's impossible to tell from ultrasound how big baby really is, and for all you know you would have a surgery for no reason. Using the measurements posted, baby's head is in the 84th percentile. While bigger than most, it's still doable. If it becomes necessary, a c-section can always be done later. They're not to be taken lightly, and if you have future children you will also likely need to have surgery done again.
Try natural first. Like Clysta said you dont know how big the baby actually is, girls on here have said Dr. predicted their baby would be 10-12 lbs. and end up giving birth to a 7 lb. baby. I went into my labor planning on natural and only have a C-section is things were not working.
My doctor said my baby maybe 3.5-3.75kg. Is it big and hard to give birth?
Well personally i would try for the c-section especially if your doctor i worried. My first birth ended in a emergency section because of his head being too big and trying to come out put him under alot of stess which caused him to stop breathing all together. (he is fine now) But listen to your gut feeling and go by what you think. If you decide on a natural birth be prepared for a c-section... not saying you will have to have one but it eases the stress knowing one might be needed rather than being shocked and clueless if you do. i'd read up on some information about it.
3.5 kg is something like 7.7 lbs. That's not big in the least. 3.75 is something like 8 lbs. This too is not a very large baby, and is the typical size for many. There was a women who vaginally birthed a 13 pound baby. Just look into both and see what you think would be best in your situation. There's pro's and con's to each one. C-section means you know exactly when baby will come, but can also mean longer recovery, more pain, risk of infection to the incision site, it could rip open later in life, pain in the area, etc. Vaginal birth can result in faster recovery, and also helps baby in the sense that the fluid in the lungs is squeezed out during the birthing process. However, you can also rip (and rip badly) baby could get stuck, baby could go into distress, etc. Just remember that what happens to one does not mean it will happen to you. I personally had a very uncomplicated vaginal delivery, and healed within 2 weeks. I ripped twice (and they were tiny) and that was the extent of the damage. Others rip straight to their anus and require a couple dozen stitches. The same can be said for a c-section. Some have very easy ones, and recover quickly. Others will get numerous infections and bad scar tissue from it, making pregnancy in the future difficult. You have to decide what's the riskier for you.
7.7 is normal size. My daughter was 7lbs and 6ounces and I pushed her out in 10 minutes. I would try for a vaginal birth. There was a lady on this board alittle while ago whose doctor told her she was having like a 10 lb baby and scared her into having a c-section. The baby came out only 8lbs and she was so upset she didn't listen to herself and have a vaginal birth.
My daughter was only 7lbs6oz but she had a HUGE head....and I had a relatively quick delivery with her. I did tear, but it was most likely due to the fact that my delivery was so very fast. Even WITH the tear, I'm glad I did a natural birth though because no matter how hard the recovery was, it was still quicker and less complicated than a c-section.
C-sections are a good option for some, but if you can try for a vaginal...I say go for it. They told me my son would be "well over 10 lbs" and that I had the option for a c-section..again, I went for a natural and I'm glad I did. he was only 7lbs10oz!