Some women are lonely in their relationship or marriage and they find themselves looking to other men to fill that emptiness in their lives. This sadly happens a lot more than some people realize. This unfortunately happens to a lot of military families where the husband or boyfriend is deployed overseas from anywhere between 6 months to a year or more. The woman finds herself in bed with another man and then her husband or boyfriend comes home to find her pregnant.
Most men in these cases will do the math to make sure that things add up and may even request a paternity test if they are suspicious or have their doubts that they are really the father of the child.
Some women know that their husband's or boyfriend's come home suffering from things like PTSD or Post Traumatic Stress Disorder, and have developed a temper that they may or may not be able to control. The woman is terrified of what her husband or boyfriend will say or do if and when he finds out not only has the wife or girlfriend been unfaithful, but that there is a chance that the baby may or may not be his.
This can also happen in cases of domestic violence. If a woman has found love outside of the relationship or marriage and has found out that she is pregnant, she might lie to her abuser to protect herself, her unborn child, and sometimes even the baby's real father.
There are so many different reasons that women might lie about the due date of their pregnancy, and most of the time what it comes down to, is that they are scared for one reason or another. They also might lie about the due date to get away from their abuser. If she knows that there is a possibility of two different father's, she might lie about the due date to make it look like the better of the possible fathers is in fact the father.
This might work until someone requests a paternity test and then the pregnant or new mother will really be backed into a corner about who truly the biological father is and then she will have a lot of explaining to do. This could result in loosing both men in her life, the good choice and the not so good choice if the good choice doesn't understand why she felt the need to lie in the first place.