Your baby's legs might correspond to 21 weeks of pregnancy while her head might indicate 20 weeks.
This is completely normal as each baby has different proportions and grows slightly differently.
Pregnancy is dated from the first day of the last menstrual period, so at four weeks, a woman is just due for a menstrual period.
At 4.5 to 5 weeks, a gestational sac may be seen in the uterus using transvaginal ultrasound, Joseph Woo, M.
The difference could mean different things depending on what stage of your pregnancy you are in: First trimester In the case of a missed miscarriage or blighted ovum, there will also be no heartbeat.
Your doctor will ask you to get a second scan to confirm this and then discuss your next steps.
An ultrasound scan estimates your baby's age by measuring different parts of your baby's body such as her head, abdomen, and legs.
Unfortunately, miscarriages are quite common in the first trimester.
It records high-frequency sound waves that create an image (see Reference 4).
Normally, ultrasounds before until week 4 of pregnancy shows nothing in the uterus and serve no purpose.
She will ask you when the first day of your last period was and from there, count how many weeks pregnant you are.
This is also how your doctor will estimate your due date by counting 40 weeks from the first day of your last period.
Transvaginal ultrasound can see embryonic development about a week before transabdominal ultrasound, the American Pregnancy Association (APA) states.