The Green family, who owns Hobby Lobby, aren't Catholics, and they don't have a broad objection to contraception. Instead, they object to methods of birth control that may also cause abortions -- which is why they didn't cover them.One of the arguments from the Left is that this is a factually false claim -- that morning-after contraceptives don't actually cause abortion. Sometimes, defenders of President Obama's contraception mandate argue that it's not an abortion to prevent a fertilized embryo from implanting. This is an odd argument based on the odd insistence that a human life becomes a human life upon implantation.

Today, on Twitter, MSNBC producer Jamil Smith objected to my writing that morning-after contraception "can function as an abortifacient. "No, smith wrote. "Morning-after pills like Plan B actually don't cause abortions. It is amazing that you and so many others still believe this."

It's not actually amazing to believe morning after pills can cause abortions. Science backs up my claim.

Read the FDA guidance on ella, one of the two morning-after pills Hobby Lobby wouldn't cover:

The likely primary mechanism of action of ulipristal acetate for emergency contraception is therefore inhibition or delay of ovulation; however, alterations to the endometrium that may affect implantation may also contribute to efficacy.

Scientific studies on how ella works are divided. A recent comprehensive study of the studies was published at the journal Reproductive Sciences concluded:

Our evaluation suggests that UPA [the active chemical in ella] succeeds in preventing the clinical appearance of pregnancies mainly by its negative effects on endometrial receptivity, which is a postfertilization mechanism.

"Endometrial receptivity" is the ability of the uterine lining to accept a fertilized egg.The morning-after pill ella works largely "postfertilization," rather than by preventing fertilization.

For one thing, the study found "that every study investigating the effects of UPA on endometrium concludes that the threshold for altering endometrial morphology is lower than that required for altering folliculogenesis."

Again, the study states:

The efficacy of UPA, reported to be able to prevent more than 80% of expected pregnancies, is thus likely to be due to the described endometrial effects that make the tissue unsuitable for embryo implantation.

As MSNBC contributor Zerlina Maxwell puts it: "omg science!"