Postponing Pregnancy

• What does the church say about postponing pregnancy?
• What is a grave reason to postpone pregnancy?
• Is this the same as birth control?

Echoing the words of Pope Paul VI, couples are to remain open to life and discern the size of their families with God. The Church encourages and teaches couples that they are co-creators with God in bringing a new human life into the world and that they should pray and discern with God and each other when that will happen. 

The Church understands that there are times when a couple is not able to bring forth a child due to grave or serious reasons.
What is an example of a "grave" reason?

Read a section of this article from the USCCB's resource, ForYourMarriage.com:

Grave and Serious
Paul VI in his encyclical Humanae vitae (1968), while condemning the use of all contraceptive methods for even grave (gravia) reasons, declared licit the recourse to the infertile periods if the spouses have good (just and seria) reasons to postpone even indefinitely another pregnancy (HV, no.16 &10; the language here is similar to Gaudium et Spes, no.10). But first, those spouses are commended who, with prudent deliberation and generosity, choose to accept a large family. The spouses are to consider their responsibilities towards God, themselves, the family, and human society. Each of these factors may be taken into account in the right order in determining “serious and just reasons.”

In other words, the spouses are to discern together first, what is God’s plan for their family here and now, then their own physical and emotional resources for accepting another child, the needs of other family members, and lastly the good of the human society in which they live. The pope gives special encouragement to scientists to perfect the natural methods (HV, no.24), declaring that the discipline of chastity exercised in periodic continence enhances married life provided the spouses value the true blessings of the family (HV, no.21).

“When Can We Use NFP?” For Your Marriage, USCCB, https://www.foryourmarriage.org/when-can-we-use-nfp/.

There may be instances that arise in which couples are not able to have another child for a short amount of time, as mentioned above. But they are encouraged to choose natural methods, like NFP, to navigate this time.

While the title "birth control" sounds like it would help couples plan their family, it is significantly less successful and effective in doing just that.

Natural Family Planning (NFP) actually has highter success rates in postponing pregnancy for just reasons (as mentioned above) than hormonal contraceptions, because couples would be avoiding intercourse during the woman's fertile window. 
Instead of guessing when a woman is fertile and can get pregnant, she can know by charting her fertility.

A woman who charts daily will be able to see when she ovulates, noting the natural signs of fertility that are present. On those days, the couple would abstain from intercourse to avoid potential pregnancy.

Want to understand your natural menstrual cycle better? Check out this article from Natural Womanhood:
Understanding Your Menstrual Cycle

To learn more about why hormonal contraceptives are less effective in preventing pregnancy, check out the study below.