The most common report that we hear from women is that in their five-week ultrasound, they see nothing. There is no fetus and no fetal heartbeat. This can be incredibly scary for anyone, even if you’ve had children already. You start wondering if you’re having a miscarriage or maybe the embryo wasn’t viable…

This is why doctors will always warn against having an ultrasound too early. Just because there isn’t anything on the ultrasound, it doesn’t mean that you aren’t pregnant. Listen to what your doctor says, and if they aren’t worried, you shouldn’t be either.

Why can’t you see anything?

At five weeks of gestation, your baby is only about the size of a sesame seed. It is so tiny that it may be quite difficult to spot within the gestational sac. Additionally, the heartbeat might be there but you just can’t pick it up because of the size of the embryo.

Remember, pregnancy is counted from the first day of your last menstruation. This means that for at least two weeks – menstruation to ovulation – you haven’t actually got a fertilized embryo. After five weeks, the embryo has only been developing for a maximum of three weeks.

Some women are lucky enough to be able to see something on the five-week scan. This is usually because they ovulated earlier than predicted and are actually slightly further along in their pregnancy than originally thought. A few days can make a big difference in whether or not you see the fetus and hear the fetal heartbeat.

When can you first hear the fetal heartbeat?

Actually being able to hear the heartbeat of your baby can come a little later than everything else. In some cases, the gestational sac, the fetal pole and the embryo are all visible but there is no heartbeat. This is completely normal up until week six or seven.

From around week six, the embryo starts to have involuntary spasms that eventually become a heartbeat. After week seven there should be a definite rhythm to the beats that can be heard via the ultrasound scan.

Anembryonic pregnancies (blighted ovum)

In some cases, not being able to see the embryo may mean that you are having what is known as an anembryonic pregnancy. This can also be referred to as a blighted ovum, but that term isn’t so popular any more.

Basically, the gestational sac has started developing but the actual embryo is not developing. There are many reasons for this happening, and usually your body is rejecting an embryo that was not viable and would not have been able to develop fully.

This condition cannot be fully diagnosed in one scan. Your doctor will have to do further testing if they suspect that this might be the case. They will do another ultrasound about a week later and also check your levels of hCG. If your hormone levels continue to rise, then there is an embryo in there, it’s just taking its time getting big enough to be seen on the ultrasound.

If your hormone levels don’t increase or even decrease, your doctor will look for signs that the body is expelling the miscarriage. If you don’t expel it naturally, you may have to undergo a procedure called curettage. This is where the doctor surgically removes the lining of the uterus.

When is the best time to go for your first ultrasound?

Most doctors won’t do an ultrasound before eight weeks of gestation. Any earlier and you risk not being able to see or hear anything. This then can easily create anxiety for the mother-to-be, which can be detrimental to the early pregnancy.

If you have a regular cycle, your doctor will be able to tell exactly when you are eight weeks pregnant. However, late ovulation can lead to you going for your first ultrasound too early. This is when you’ll likely only see the gestational sac and nothing else. It’s best not to panic, especially if your doctor is sure that you are just a little too early to see the embryo.

The good news is, if you don’t see anything on your ultrasound, you’ll likely only have to wait about a week to see some changes. Your pregnancy will develop quite rapidly in weeks five to eight. Your doctor will tell you when to come back and what you should expect to see then.

IMPORTANT: An ultrasound at week five can sometimes do more damage than good. It’s best to wait until week eight to ensure that you will see something.

If you aren’t sure about when to go for your ultrasound, ask your doctor about getting a beta-hCG blood test done. This will show you how much of the hormone is in your system and give an indication of how many weeks pregnant you are. Results of over 5000mlU/ml should mean that you are far enough along to see the embryo and hear the heartbeat.

Readers’ questions:

What does my baby look like after five weeks of gestation?

Your baby is still very small – about the size of a sesame seed. It has no recognizable shape to it as the cells are still in the early dividing stage. There is a fetal pole at this stage, which will develop into the brain and spinal cord.

What is the size of the gestational sac at five weeks of gestation?

The gestational sac is now between 4mm and 16mm in diameter. It is growing rapidly at this point and can double in size in the course of one week.