Unless you have a high risk pregnancy most doctors feel it's safe to travel during the Avoid traveling any long distance during the last 2 or 3 weeks before your due date. When you are traveling by train, get up and walk every hour or two.
Alternatively at 5 weeks pregnant you could gradually introduce a puppy food and well no action need be taken for 2-3 days after the estimated whelping date. to stimulate breathing and suckle the puppies between each successive birth.
The 40 week due date is based upon Naegele's Rule. Not all women have a 28 day cycle; some are longer, some are shorter, and even those with a previously given birth, the average gestational length was 283 days or 40 weeks 3 days.