Child Spacing Calculator

What the interval means medically

Health guidance generally focuses on the interpregnancy interval — the gap between giving birth and conceiving again, rather than between the children's birthdays.

Most guidance suggests waiting at least 18 months after a birth before conceiving again, and some recommends 18 to 24 months. Shorter intervals, particularly under 6 months, are associated with somewhat higher rates of preterm birth, low birth weight, and maternal anaemia.

Very long intervals — beyond about 5 years — have also been associated with slightly increased risks in some research, though the effects are smaller and less consistent.

These are population-level associations, not predictions about any individual pregnancy. Plenty of closely spaced pregnancies go entirely well. If you conceive sooner than planned, that is a reason for good antenatal care rather than alarm.

After a caesarean

If your first birth was by caesarean, the recommended interval is generally longer to allow the scar to heal fully. Many guidelines suggest waiting at least 12 to 18 months from the caesarean to conception, particularly if you hope to attempt a vaginal birth afterwards.

Shorter intervals after a caesarean carry a somewhat higher risk of uterine rupture during a subsequent labour. This is a conversation worth having specifically with your obstetrician, since individual circumstances vary considerably.

What different gaps tend to feel like

These are generalisations with enormous individual variation, but they capture common patterns.

Under 18 months. Intensely demanding in the early years — two children in nappies, neither able to walk far, and no break in the physically hardest phase. Many families report the children become close companions, and the demanding period, while brutal, is over sooner.

2 to 3 years. The most common gap. The first child has some independence and language, though may still be in nappies and is often in the middle of toddler behaviour. Frequently described as a reasonable middle ground.

3 to 5 years. The first child is usually independent in eating, walking, and often toilet-trained, and may be at nursery or school. Considerably easier practically. The children play together less as peers and more as older and younger.

Over 5 years. Almost like starting again, with the advantage of an older child who can genuinely help and does not compete for the same attention. Shared childhood play is limited.

Practical factors worth weighing

• Childcare costs — closely spaced children mean paying for two places simultaneously, which is a large expense for a shorter total period. Wider gaps spread the cost.
• Career timing — consecutive leaves keep the disruption in one block; spaced leaves mean returning and leaving again.
• Equipment — close gaps often mean buying a double pram and a second cot; wider gaps allow reuse.
• Your recovery — physical recovery from birth and breastfeeding, and sleep debt, are real considerations that get less attention than they deserve.
• Age and fertility — if you are older or conception took time previously, waiting carries its own risk.

A note on planning

Conception timing is not fully controllable, which is worth holding lightly. Some families conceive immediately and some take far longer than expected, and a plan that assumes precision often becomes a source of disappointment.

There is also no gap that produces better outcomes for children overall. Research on sibling relationships and child development finds no clearly superior spacing — family dynamics, attention, and circumstances matter far more than the interval.

Whatever gap you end up with, planned or otherwise, families make it work. If you are trying to conceive and it is taking longer than expected, or if you have questions about spacing after a difficult birth, your GP is the right person to speak to.

Common Questions