Heartbeat at 18 days?

While on a recent trip to Florida, I saw a number of billboards, saying that an embryo had a heart at 18 days of age.

I could not find this ad campaign on the Internet, but I found a web page, which makes this claim, among others: "18 days after conception the baby's heart is beating." The organization's web site indicates that this is an Irish pro-life organization. (By September 28, 2013, this web page had been removed, which is hardly surprising, considering the nearly four years since I saw it.)
Both the web site and the billboard campaign show a picture of a fetus, not an embryo. (The human becomes a fetus at eight weeks of pregnancy.) So does the heart really beat at 18 days?

The Wikipedia article on prenatal development is a good source for answering this question. It's a little confusing, because it gives both the age of the embryo/fetus and the gestational age, which is the time since the last menstruation.

According to that source, "Primitive heart tube is forming. Vasculature begins to develop in embryonic disc." at 20 days after fertilization, not 18 days. (Vasculature means the blood vessels needed for circulation.) The heart begins to beat between 22 and 28 days after fertilization. However, the first sign of a working circulatory system is later than that, at between days 29 and 35.

The billboard campaign, and the web page, seem to be wrong. The heart doesn't begin to beat until later than 18 days after fertilization, and it doesn't really start to function until even later than that. Besides, the graphic in both the web page and the billboard show a fetus, probably at least 12 weeks old, not an embryo at all.

There are reasons for arguing that unborn human entities should be protected, and I won't consider the validity of those reasons here. But, even if those reasons were completely uncontroversial arguments, that would not excuse the use of distortion in support of protecting embryos or fetuses, and that, unfortunately, is what the pro-life community has done, in the two instances described, and, I'm afraid, in other cases.

Thanks for reading. See here for a more comprehensive view of my thoughts on abortion.