Short answer
There is no general requirement that every married couple must have a child immediately after Nikah. Decisions about timing of children involve the circumstances and responsibilities of the couple.
Islamic Guidance
What Islam teaches
Islam encourages family formation and regards children as a blessing, while Islamic scholarship has also discussed temporary pregnancy prevention. Couples should not treat childbearing as merely a social competition.
Practical Guidance
What you can consider
Husband and wife should discuss their plans privately and respectfully rather than allowing unnecessary external pressure to determine their family decisions.
Sources
Qur'an 42:49-50; Sahih Muslim, Book of Marriage.