 Why didn't the Lieutenant know she was pregnant?
Once every two hours, the artificial satellite looped completely around the planet, watching what went on below. Outside its bright steel hull was the silence of the interplanetary vacuum; inside, in the hospital ward, Lieutenant Alice Britton clutched at the sheets of her bed in pain, then relaxed as it faded away. "Lieutenant Britton, it is my personal opinion that you need your head examined, and not by a general practitioner, either! According to the major, the baby was due sometime around the first of September. And then, only half an hour ago, a meteor had hit the radar room. The depressurization hadn't hurt her too much, but the shock had been enough to start labor.
 She has an irregular cycle.
 She has an irregular cycle.  She had her tubes tied before going into space.  She wasn't keeping track of her cycle.  Women don't have periods in space.