With greater reproductive control comes more options — which sometimes just means more questions. As more and more women are juggling a career and family — and in a work environment that has yet to prove it’s ability to retain working mothers — identifying the best age to get pregnant has never seemed more important.

In theory, there is no ideal age for pregnancy; a perfect world would have an individualized perfect age for pregnancy that varies from couple to couple. But in the real world, there are biological constraints, as well as social factors that will influence your reproductive decisions.

It starts by figuring out what you mean by ‘best’ when you ask what is the best age to have a baby; this answer will vary — typically across four considerations — from person to person, and couple to couple. Let’s walk through the evidence around each one.

What is the best age to get pregnant?

In terms of fertility

Most women’s top concern regarding the right age for pregnancy is biological, for good reason — we’re all born with a finite number of eggs, and lose one with each menstrual cycle. Other biological changes associated with age also make conceiving and carrying a baby to term more difficult.

It’s difficult to pin down an ideal age for fertility. Most experts agree there’s a best age range for pregnancy, when fertility is at its peak: between 20 and 35 years of age. While fertility does decrease during this time, your chances of getting pregnant within any given year are still good: 75% of women at age 30 will be able to conceive naturally and have a baby in this time frame; at age 35, 66% of women will be able to do so. After 35, natural conception becomes more difficult, and the chances of genetic disorders and miscarriage rise.

An important — and overlooked — factor in this definition of the ideal age for pregnancy is the age of the father. Men’s fertility also declines with age, which can lead to the same conception, genetic and miscarriage issues. The best age for a man to get a partner pregnant is before he’s 40.

In terms of the baby’s health

The same age range applies here. A 2011 study across 72 countries examining the relationship between a mother’s age at first birth and infant health outcomes concluded that the riskiest age for a woman to have a baby was in her teens. Children’s health improved slightly as the mother’s age at first birth rose to 27, but not in a statistically significant way. After age 27, the relation between children’s health and age at first birth appeared to level off.

That said, the study only compared maternal age to children’s physical health, specifically risk of mortality, stunting, underweight, wasting, diarrhoea and anaemia. Getting pregnant after age 35 is associated with a higher risk of preterm birth (which itself carries associated effects on children’s health) and an increased chance of cognitive or mental health issues like autism, schizophrenia, and Down syndrome.

Again, the perfect age for pregnancy isn’t just something women have to worry about. Paternal age past 40 at conception has also been associated with many of these adverse outcomes as well.

In terms of your health

Pregnancy and motherhood takes a toll on women’s bodies, so it’s worth considering the right age for pregnancy from this angle, too. A 2005 study pins the best age to have a first baby at 29 to 34, in terms of mother’s health. Women who gave birth for the first time within this age range reported fewer aches and pains, better overall health, and fewer chronic diseases in middle and old age, than women who were younger or older at the time of their first birth.

If you’re interested in having more than one child, then it’s also important to consider the health effects associated with maternal age at last birth, too. One 2002 study found that women who gave birth beyond age 35 had higher blood pressure, higher blood glucose levels, and generally poorer health than women who did not give birth past 35.

In terms of parenting

Finally, becoming a parent is not just about fertility, delivery and health, but also about the actual nurturing of a child into a functional adult. So, the best age to have a baby can be weighed from this perspective, too. Studies suggest the older a parent is, the better at parenting they tend to be, opting for a more authoritative style — that is, one that sets boundaries, but offers explanations and emotional warmth and support — rather than an authoritarian ‘my way or the highway’ style.

Older parental age has also been linked to better behavior and more advanced academic performance. This is attributed in part to the fact that older parents tend to be more emotionally mature, better educated, more financially secure, and in more settled relationships, allowing them to provide more stable and supportive environments for children.

In the end, these age ranges are a guide, not a rule of thumb for pregnancy age. Only you and your partner can decide what is the best age to have a baby based on your priorities, experiences, and circumstances.