During early weeks of pregnancy, common symptoms to appear, include fatigue, mood changes, breast tenderness, nausea, cramping, and food aversions. Some women even notice signs of pregnancy as early as five days after ovulation. However, others discover they have conceived much later. Nearly a quarter of women are unaware that they're pregnant until the seven-week mark or after. Of these cases, cryptic pregnancies are the most extreme. Cryptic pregnancies are pregnancies without any obvious symptoms. A woman may not realize she's pregnant until the second or third trimester or even later. In recent studies
published in the Journal of the Royal Society of Medicine reported that between 1 in 475 and 1 in 516 people experience a cryptic pregnancy at 20 weeks. Extrapolating this therefore equates to 1 in 2,500 are unaware that they are pregnant or until they go into labor. The possible risk factors that are associated with this anomaly include being young, receiving less formal education, being single, and having a history of mental health conditions. The American Pregnancy Association explains that many people get pregnant even though they believed or were told they were infertile. Therefore, it is imperative that early detection can prevent complications, so it is important to take a pregnancy test after a missed period and to see a doctor when experiencing any new or unusual symptoms.
Ref:
https://www.healthdigest.com/897292/signs-you-should-take-a-pregnancy-test/ 
