• I had my first child at 31 and my fourth — and final — child at 40.
• There were a few things I didn't expect about having a kid again, almost 10 years later.
• Pregnancy and delivery were surprisingly easy, but my friendships have suffered.

I always knew I wanted a big family, but I wasn't in a rush to get started. When I got married in my mid-20s, after a prolonged time in school earning two graduate degrees, I wasn't quite ready to have children. I wanted to become more established in my career, pay down student loans, and travel before kids entered the picture.

Then, at 31, I had my first child, followed quickly by two more. I loved being a mother. Yet, even with three children who were my moon and stars, I didn't feel as though my family was complete. It took my husband a few years to get on board, but we eventually agreed to grow our family by one more, and I had my last son just before turning 40.

I wouldn't change a thing, but I didn't fully consider the implications of having a child at almost 40.

Pregnancy and delivery went smoothly

When I had my son, I was ecstatic that my much-wanted fourth and final child had arrived. I drank in his newborn scent. Even though I was older, I found late-night wake-ups and cluster feeding easier and less intrusive than I had with my older kids. Having waited so long for my son and knowing he was my last made every moment with my baby seem just a little sweeter.

Although I was considered a "geriatric mother," my pregnancy and delivery had gone smoothly. Even as a 40-year-old mom, I didn't feel my age, even though there was nearly a decade between becoming pregnant with my first child and giving birth to my fourth.

My friendships suffered

I knew, logically, that being an older mom would have its challenges. However, I didn't fully understand the implications, and they didn't become apparent until my son was a little older. By the time I had my last child, most of my friends had their days free outside of work. They were regularly getting together for coffee breaks, lunch dates, and dinners out. Although bringing a baby along was usually possible and often welcome, once he became a mobile, chatty toddler, I had to decline more invitations. My friendships suffered.

Even now, years after my son started school, I find it hard to relate to many of my friends' lives. While I am still in the thick of raising an elementary-school-aged child, they are no longer making school lunches, chauffeuring their kids to sports practice, and looking over homework every night.

While most of my friends still have children at home, their kids are largely self-sufficient, leaving them with the kind of free time I can only dream about. Last year, some friends planned a girls' trip, but I declined to go because it would be difficult to leave my son for so long. My friends understood but went anyway.

My son keeps me young, but I worry constantly about not being around for him

I love that having a child in elementary school keeps me active and engaged. We still go ice skating together, and unlike my teenagers, my youngest actually wants to tell me about his day and snuggle on the sofa.

However, I worry constantly about not being around long enough for my son as he grows up and starts his own family. I sometimes mourn the relationship I will never have with his children and feel sad that my grandchildren probably won't have grandparents around to spoil them.

My own parents were so supportive of me when I started my family and never hesitated to step in to help. They shower my kids with love.

Because of my age, it's unlikely I will be able to do the same for my children and grandchildren for very long, particularly for my youngest son. Although I knew a more limited time together was a reality when I decided to have a child at nearly 40, I feel the loss more acutely, seeing how quickly time is speeding by.

I still wouldn't change a thing

Although I keep being surprised by the implications of having a baby later in life, I don't regret a thing. With his late arrival, my son completed our family. He brings my entire family so much joy, and it's hard to imagine life without him. There are also advantages to having a child later in life. We are more financially stable, I have more perspective on what truly matters, and he keeps me young at heart. All of this helps me enjoy motherhood a little more than I did with my older kids, who were born when I was younger.