Smulders plays Robin on the sit-com "How I Met Your Mother." Killam, who has appeared on the series with Smulders, is best known for his roles on the sketch comedy series "MADtv" and "Short Circuitz."
The actress is due to give birth in late spring, Smulders' representative told People magazine exclusively.
Her co-star Alyson Hannigan also recently announced she and her husband Alexis Denisof are expecting their first child.
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