Popular hCG diet results in false positives on pregnancy tests

It's not commonly known, but one effect of the popular yet controversial hCG diet is it can cause false positives on pregnancy tests because of the ingestion of the hCG hormone (derived from pregnant women). Human chorionic gonadotropin is, of course, the hormone secreted by the implanted embryo and detected in the pregnant woman's urine by pregnancy tests. HCG from the diet stays in a woman's body up to 30 days. Should a woman who is on the hCG diet doubt the results of a pregnancy test, she should seek blood serum or ultrasound verification of pregnancy.

The hCG diet compounds the situation for women who think they might be pregnant due to the severity of its calorie restrictions. At only 500 per day, a woman may undergo changes in her reproductive system. She may not ovulate or even have a period. So, it's not known whether she even can get pregnant on the diet, or whether the diet would further mask a pregnancy.

The Food and Drug Administration warns pregnant women not to use the hCG diet because it can cause severe birth defects. Presumably women should also be warned not to become pregnant while on the hCG diet. It is listed as a "category X" teratogen.

• Update: FDA says OTC sales of HCG diet products are illegal
• N Miami Beach abortion clinic offers abortion in one room, pregnancy hormone to lose weight in another

What does this mean for pregnancy care centers? What should volunteer advisors say to a woman who may be pregnant while on the hCG diet? How should they counsel a woman who has a positive pregnancy test and is on the hCH diet? Should PCCs ask women whether they are on the hCG diet when a test is positive? What's the protocol if she is?

Postscript: After posting this question on the discussion page for the Pregnancy Center Leadership group on LinkedIn, I received helpful responses from Karen at a Houston-area center. Interestingly, this is the region from whence the original query came, so Texas must be a hot-bed for the hCG diet. Karen said:

We added the hCG question to the medical history on the intake. We have already had a client on the diet who said she had not tested positive for pregnancy while on it. She had been off the diet for 3 weeks, had a positive urine test with us so we performed an ultrasound for confirmation. (She was pregnant.) Our medical director has requested we ask any client who is on the hCG diet to go off of it for one week and then return for a retest. Then we will handle as usual if her urine test shows positive. I've been told by other volunteers that the hCG diet is very popular in our area.

This seems to be a wise protocol. I then asked Karen if she recommended that all centers adopt it, or only those in regions where the diet is popular. She said she thought "all pregnancy centers should talk with their medical directors ASAP and find out how he or she wants this handled. Other pregnancy centers [non-medical] should consult a supporting ob/gyn for direction."