How was birth control realized in ancient days?
The need for birth control has been a concept for thousands of years and remains an important issue for men and women today, the need for contraception helped humans to achieve control over our population and healthy sexual relationships without having the fear of pregnancy.
The medieval contraception methods mostly relies on plant based oral contraceptives and also plant based suppositories. There is always an element of myth in the usage of these medicines to control child birth, but due to the overusage of Silphion, the plant was gone extinct.

Silphion was a plant that grew in the hills near the Greek city-state of Cyrene located in North Africa. This plant was one example of an oral contraceptive in ancient times, based partly on Pliny's statement that it could be used &quot;to promote the menstrual discharge&quot; but since then has been harvested into extinction.
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Asafoetida is widely used as a  contraceptive in medieval period, Asafoetida or asafetida is the dried latex exuded from the rhizome or tap root of several species of Ferula.

One of the earliest contraceptive pioneers was Soranus of Ephesus, a Greek physician of the 2nd century C.E. who practiced in Rome and wrote extensively on obstetrics, gynecology and pediatrics. Many of his texts exist to this day which describes plants that were recommended for use as oral contraceptives, suppositories and abortifacients: galbanum, silphium, opopanax, myrtle, rue, white pepper, cow parsnip and pomegranate.
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Also condom is not a modern mechanism it was used in ancient times, but the usage was to protect oneself from sexually transmitted diseases, but an unknown chemical used  which is a spermicide and this resulted in contraception.

Records of condom use dates back to 3000 B.C. where King Minos of Crete, son of Zeus and Europa, utilized the bladders of goats to protect himself during intercourse.
In the 1500s, a syphilis epidemic spread across Europe. It was at this time that Gabriel Fallopius,created a linen
condom as a means to protect from the continuing spread of disease . This proved especially effective when soaked in an unknown chemical solution acting as a spermicide.
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The medieval contraception methods includes,

Condoms
Female Barrier Methods
Herbs and Rituals
Intrauterine devices
Male methods
The Pill

These methods are widely described in this article.