During pregnancy, the pregnant woman undergoes certain physiological changes that are necessary for the adaptation of the woman to the pregnant state, thus ensuring good fetal development and growth. These changes include several functions; endocrine, metabolic, hepatic, renal...etc.

For more details, I refer you to these articles:

Article Physiologic and Pharmacokinetic Changes in Pregnancy

Article Physiological changes in pregnancy

75% of women have no menstrual bleeding during pregnancy. 25% have bleeding.

Hi, Ahmed. Take a look at these two papers:Article Physiological changes in pregnancy

https://www.frontiersin.org/articles/10.3389/fphar.2014.00065/full

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Best regards,

Silvia

Hi Ahmed,

Pregnancy and its changes are a normal process that happens in all mammals. During Pregnancy several changes occur in the mother to nurture the development of the foetus and prepare the mother for labour and delivery. Physiological changes are one of them which include;- Airway changes (for example The nasal mucosa is engorged, which means there is greater resistance to flow) Respiratory changes(the diaphragm is pushed by 4 cm, respiratory rate increases 15-17) Circulatory changes(Cardiac output increases (from 5L/min to 7L/min) Electrolyte and endocrine changes(cortisol secretion increased). Hematological and renal changes are also some of the physiological changes which occur during pregnancy. (Ref By Alex Yartsev - Apr 14, 2017, Last updated Sun, 06/18/2017 - 04:17 Topic: Pregnancy, Obstetrics and Gynaecology)

There are important changes during pregnancy. In relation to the breasts, a very marked sensitivity in the nipples at the beginning, which makes you suspect pregnancy, especially if associated with amenorrhea.