By Breia Brissey
Updated September 30, 2011 at 01:30 PM EDT

During last week’s season three premiere of Sister Wives, Kody Brown and wife No. 4, Robyn, revealed that she was pregnant with their first child together. (Robyn has three children from a previous marriage.) But during Sunday’s two new back-to-back episodes, Robyn realizes she’s spotting, and fears of pregnancy complications set in. In this exclusive clip, Kody and Robyn meet with their midwife to see what’s wrong, and the midwife is unable to find the baby’s heartbeat. “There’s kind of a threat of miscarriage,” says Kody. “And it’s got us both a little spooked… Now we’re just trying to figure out what’s going on, and we’re dealing with a very, very heavy unknown.”

Two new episodes “Teen Sex Talk” and “4 Houses, 4 Relationships” air this Sunday on TLC at 9 p.m.

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