The most common report from people who have a 5-week ultrasound is the absence of the fetus, and consequently, panic! Is the pregnancy not viable, is it anembryonic, will it work out, what if, what if, what if… The risk of having an ultrasound this early is exactly that, not being able to detect the baby, let alone his or her heartbeat.
We have to keep in mind that pregnancy is counted from the first day of the menstrual period and that the fetus is formed by two cells (egg and sperm) which are very, very small, right? So, at a 5-week pregnancy, the baby is at most 3 weeks old and is certainly still too small to be visualized on the ultrasound.
How Pregnancy Begins
At first, pregnancy is manifested by the thickening of the endometrium and showing the area where ovulation has occurred. There may be only one corpus luteum in the ovary, indicating that the egg was released and suggesting that fertilization possibly happened1.
Some lucky women who ovulate earlier than expected may see a little mark from the start of the gestational sac, since it appears before the embryo itself. Over the next few days, the yolk sac comes into view and soon after, the baby finally appears.
When Can You See the Fetal Heartbeat?
Hearing the baby’s heartbeat is another new adventure for pregnant women. Some women see everything, gestational sac, yolk sac, embryo, but not the heartbeat. This mostly happens because the embryo is still too premature. The baby’s heart starts beating from involuntary spasms around the 6th to 7th week of pregnancy2.
For this reason, having an ultrasound before this period is not recommended, since there’s a risk of not seeing anything or, at most, just the gestational sac. To avoid unnecessary worry, wait for the right time.
Anembryonic Pregnancy
Some cases of precocious ultrasound can be associated with an anembryonic pregnancy3, but it’s still necessary to wait 1 week to 10 days for another ultrasound to actually detect if there is a problem. In the vast majority of cases, the baby is seen within a few days after the 5-week ultrasound, usually about 7 days later.
If the baby is still not detected, the doctor may suspect an anembryonic pregnancy, but before any procedure, a repeat beta quantitative HCG test should be done to verify the hormonal progression. If hormone levels continue to rise, you should wait and repeat the ultrasound. If there is no progression, the doctor will request a procedure called a curettage or wait for the body to expel the pregnancy remnants naturally.
What Is the Best Time to Have an Ultrasound?
The best time to have an ultrasound is at the 8th week of pregnancy, counted from the first day of your period. Some say the sooner you do an ultrasound, the better, but that’s not really true! Even at this stage, there’s a risk that you won’t see the baby, just a gestational sac at 5 weeks, or not even that, especially due to the risk of late ovulation, which is common in women with longer cycles or issues such as PCOS.
That’s why you shouldn’t panic if your first ultrasound shows no evidence of pregnancy.
If your cycle is regular, the pregnancy can usually be seen around the 8th week, but for irregular cycles, the likelihood of seeing the baby and hearing the heartbeat drops significantly. If nothing can be seen on the 5-week ultrasound and your cycle is irregular, it’s recommended to wait a few more days and try not to worry, as it’s very common for a woman with just a few weeks of pregnancy not to see anything, not even the gestational sac!
IMPORTANT: at 5 weeks, an ultrasound may do more harm than good. That’s why you should never do a beta HCG and immediately rush to the scan. The likelihood of not seeing anything is very high!
An American study indicates that the chances of seeing the embryo on an ultrasound are related to the amount of HCG in your body; betas above 5,000 may show the baby and the heartbeat, while below 1,000, not even a gestational sac may be evident. But, of course, this varies from body to body.
Want to know how your baby is at 5 weeks of pregnancy? Then see here in the fetal development for the 5th week.
Readers’ Questions:
What is my baby like at 5 weeks of pregnancy?
At 5 weeks, you might be able to see a gestational sac and the yolk sac, which are tiny, like a sesame seed. There is no baby shape or any resemblance yet. The neural tube is developing and will become the brain, spinal cord, and nerves.
What is the size of the gestational sac at 5 weeks of pregnancy?
At 5 weeks, the average diameter of a gestational sac is around 25 mm and can double in size over the week.
Important Tip: at this uncertain stage, it’s essential to keep your beta HCG levels tested regularly, ideally every 2 or 3 days. If in doubt, repeat the test, and if the hormone is rising, it’s a good sign.
