Spacing Babies: What’s the Ideal Interval Between Pregnancies?

How to decide what’s best for you, your body, and your family? You know how you’ll decorate the nursery, which baby names you want, even what daycare your infant will attend. But do you know when to have a subsequent child?

Is there an ideal age difference between siblings, and if so what is it? While opinions on the matter are strong, they vary. In reality, everyone’s situation is unique, but here are factors to consider in making your own decision about the size and timing of your family.

Ilona*, an Internet producer in Toronto, Canada, is expecting her second child three years after the birth of her son, Max. For her, cost was a big factor in the timing of baby number two. “Full-time daycare for two is costly,” she says. “By the time my second child goes into daycare, at approximately eight months, Max will be entering junior kindergarten, which is free.”

For Debbie, a mother of two in Montreal, neither pregnancy was planned but certainly wanted. “I was told before I got pregnant that my chances of conceiving were very low so I did not use any birth control, even after the birth of my first child. Then I got pregnant with my second child 15 months later.”

Health Concerns

Whether or not pregnancies are planned, the interval between them may dictate the health of mother and child. “The risks of low birth weight, prematurity, and small size are higher [when subsequent pregnancies are] between zero to three months and greater than five years,” says Dr. Kristie L. Milowic, MD, a clinical fellow in developmental and behavioral pediatrics at the Center for Development and Learning at the University of North Carolina.

According to a study by the Centers for Disease Control and Prevention, published in the February 25, 1999, issue of the New England Journal of Medicine, the recommended interval between pregnancies is 18 to 23 months. Those who became pregnant within six months of giving birth had a 30 to 40 percent greater chance of delivering a premature baby or a child small in size. The risks also increased significantly for mothers who waited 10 years. These women were twice as likely to have undersized babies and had a 50 percent greater chance of delivering prematurely. The study examined 173,205 births in Utah from 1989 to 1996, with the majority of mothers being white. The results may not be the same for minorities or for high-risk pregnancies. A second study to account for this deficiency is currently underway.

A South American study suggested that women who waited too long [to conceive a subsequent baby] had a greater likelihood of having an adverse maternal outcome, such as preeclampsia or eclampsia,” says Dr. Christine M. Derzko, MD, associate professor OB-GYN and Internal Medicine at University of Toronto and head of the division of Reproductive Endocrinology and Infertility at St. Michael’s Hospital in Toronto. Preeclampsia results in swelling, elevated blood pressure, and protein in the urine during pregnancy. With eclampsia, seizures occur during the third trimester.

Greater spacing between pregnancies decreases the benefits gained from a previous pregnancy, such as an already enlarged uterus and increased blood flow to the womb. With shorter spacing, however, a new mother may not have time to recover from vitamin depletion, blood loss, reproductive-system damage or other postpartum problems. A short post-cesarean section interval can result in uterine rupture, says Dr. Derzko. And, in either type of delivery, it may be harder for a woman to return to her normal weight.

A woman’s body sometimes provides a “natural spacing” between pregnancies as nursing can suppress ovulation, says Dr. Milowic; however, this system is certainly not foolproof, she adds, and is dependent on how much and how often a mother breastfeeds.

Logistical Concerns

Family needs may also impact spacing. When determining the timing of a subsequent pregnancy, many parents consider factors such as finances, employment, and age. Dr. Derzko, the mother of four (ages 31, 30, 23 and 21), spaced her pregnancies around work. “The first two were prior to starting residency in OB-GYN; the second two were when I was finished.”

Similarly, Dr. Milowic, the mother of three kids (ages seven, five and four), says she and her husband made a conscious decision to have their children close together since they had married older and already had careers. Milowic had her children before returning to residency. “It was very rough to have three kids in diapers. The first six months are literally a blur,” she says.

While some parents want to get the diaper phase and nighttime wakings out of the way, others want to avoid having two kids in college at the same time. Some parents also prefer to wait until the older child is a bit more independent, is able to understand, and even wants another child in the home, as Ilona’s son does. “Max has a real sense of himself as both our child and as an individual, which I think will help to reduce any fears he may have of losing any of our affection,” she says. “By the time the baby comes [Max will] be old enough to help us a bit with taking care of him or her, which should be a source of pride and accomplishment for him.”

Sibling Relations

Pat, a book editor in New York and mother of three (ages 40, 38 and 32), believed her two oldest would be playmates and the best of friends growing up. Instead, she says, having her babies so close together “was very hard on the oldest child because she didn’t have enough time to be the center of attention.”

“With children that are closely spaced, there is a tendency to parent them together, to push the older one to grow up a little faster, to become more independent because [he or she is] looking after the younger one,” says Dr. Milowic. While her own children are close and share a lot in common, she does see some rivalry. But, she adds, “I think they learn the art of negotiation, they learn how to share, and they learn early on how to deal with other people.”

Dr. Derzko and Pat also noticed sibling rivalry between their closely-spaced children during childhood. Now that their kids are older and some have children of their own, both mothers observe that their kids have become quite close.

With even greater spacing, from four to ten years, there may be a tendency for older children to tire of being the big helpers and permanent babysitters, and become frustrated with toddlers who continually mess up their personal possessions.

When she was growing up, Dr. Derzko felt the five-year difference between her and her younger sister was too much. In her own children though, “the younger ones almost ‘hero worship’ the two older ones, and the older two certainly are both fond and full of respect for the accomplishments of their younger siblings.”

For John, Pat’s youngest child, the spacing also worked out well. “By the time he was 10, Christine [the second child] was leaving for college,” she says. “Between the years of 10 to 17 he had us completely to himself.”

Can You Handle It?

When deciding how to space pregnancies, it mostly comes down to the overall physical stamina of a mom. Only a mother knows her body well enough to determine whether she can care for two young children at the same time. What the parents want and what a mother can bear, rather than the age difference between children, is most important. (Check out our quiz, Are You Ready for Another Baby?)

Having two children too close together is like having twins,” says Pat. Having a third several years later, “gave me, as a mother, a chance to breathe.”

In the end, of course, “You can plan all you want, but people don’t necessarily get pregnant when they want to,” says Dr. Milowic. “Keep an open mind.”

*Some names have been changed.

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