question about village of the dammned (remake with christopher reeve}

In the remake movie of village of the dammned starting christopher reeve what was that shadow in the beginning of the movie passing each house? And why did everyone suddenly pass out? and why were they all pregnent? what made them pregnent? Sorry about my ignorence! Could never understand the movie. can someone answer all these questions for me to the best of his or her knoweledge. I reaaly would like to know! Thanks! pazrags