There are times when we give patients the results of in vitro fertilization, we tell them that the test is positive but that it is not good news, and that the chances that it evolves into an ongoing pregnancy are slim. It is a very difficult situation, emotionally, since it is very hard for patients to understand what has happened. If it really is positive, then why isn’t that good news? If it’s not good news, then why do I still have to take medication?
Most of these cases will show a negative result some days later, and it is considered a chemical pregnancy. What has happened is that there was implantation of the embryo (if not the bHCG could not have come back positive) and the embryo stopped developing some days later. This is simply a very early miscarriage, so early that it cannot be confirmed via ultrasound, and is resolved without any medication or D&C.
This situation occurs in around 10% of IVF cycles. This means that around 1 in 10 embryo transfers, the pregnancy test is positive but the pregnancy will never be seen on an ultrasound. This is clearly linked to the bHCG levels taken 8-10 days after embryo transfer, but must be confirmed a few days later with another test, as we explained previously.
These “chemical pregnancies” are not only in assisted reproduction, but also occur naturally in spontaneous pregnancies. The majority of them are undiagnosed, because women confuse them with delays in their period. However with new pregnancy tests, which are getting more sensitive, women more frequently are seeing unclear or positive results then are then negative a few days later. This should be seen as a natural part of reproduction: just as some embryos are unable to implant, others that do are not able to continue their development, and never seen on an ultrasound.
Patients are obviously full of doubts when this situation arises: what consequences does this have in the future? Is this an obstacle in trying to obtain a pregnancy? Does it lessen the chances in a future attempt?
The answers we can give based on scientific evidence are quite positive. Couple who have a positive result have a better prognosis in future attempts. This has been proven in a number of publications and should be explained to patients so that it is taken into account when making a decision.
Even though it does not mean anything negative in the reproductive future of a couple, many chemical pregnancies cause a sense of “loss” that adds to the emotional burden already present for people with fertility problems. This is why we should always be present for any concerns that these patients may have, and give them all the necessary information that they need to overcome the situation and continue to try and reach their goal.
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