It's possible to get pregnant without having a menstrual cycle, such as during breastfeeding or if a woman has a medical condition affecting her periods.
It depends if she had copulated with someone, then it is possible to get pregnant. If they are regular in having a menstrual period, she needs to wait for three months to confirm it. Sometimes it is common for those women who have the irregular menstrual periods, so it is not a sign of being pregnant.
I do agree that women have all the moments emotionally when having their magic day. That's the reason why they need to have regular checkups especially for those who have irregular menstrual periods.
The length of time between each period is similar. However, for some women, the time between periods and the amount of blood shed very considerably. This is known as irregular menstruation.
Delayed periods cause pregnancy, stress, sudden weight loss or overweight, hormonal imbalance, and polycystic ovary syndrome. However, you need to consult a doctor if the irregularity is persistent and has no apparent cause.