If you can time a second pregnancy between 18 and 23 months after you first give birth, that may be best for the new baby's health, research suggests.
Conceiving less than 17 months after giving birth can carry a bit more risk of your baby being born prematurely and underweight: the risk is biggest if the gap is less than six months.
If you wait more than five years after a previous birth to have another baby, that can also make a premature or underweight birth a bit more likely.
benefits of bigger age gaps
Some mums swear by waiting until the firstborn is older before trying for a sibling. They think an older child will be able to cope with having a new baby at home better.
An older first child will understand more and you might be able to talk it over with them first. Plus, they've had plenty of time with you already! You may also appreciate being able to give your body more time to recover. And the same can be true of the family finances.
why small age gaps work
Other families find they really benefit from having siblings who are close in age. They're more likely to become fast friends and playmates who will share interests and look out for each other.
Some parents appreciate squeezing those messy, tiring nappy years into a single, shorter period of time, even if it is pretty exhausting at the time. You may also find it's easier to organise childcare for children of similar ages.
watching your biological clock
If you have your first child when you're older, that might affect your decision about when to try for a sibling. It's not something that the under-30s are likely to have to factor in, but fertility declines significantly after 35. So if you've had your first child after then and would like a second, you might want to start as soon as your health allows.
Many women still conceive successfully in their 40s, however, so longer age gaps may still be possible.