If You're Short and Pregnant, You May Have a Shorter Pregnancy

If you're small, it makes sense that your baby would be smaller, too, right? August 2015 research published in the journal PLOS Medicine finds that not only do shorter people have babies with lower birth weights and lengths—but the duration of their pregnancy is actually shorter as well.

This means that being shorter in stature may be a risk factor for preterm birth. Read on to learn what short pregnant people should know about how stature influences the length of pregnancy.

What Causes Short Pregnancies for Short Pregnant People?

Scientists at the March of Dimes Prematurity Research Center Ohio Collaborative studied over 3,000 Nordic gestational parents and babies. They found an interesting link between maternal height and babies born early.

"As part of our genetic studies of factors that increase the risk for preterm birth, we collect other information about the mothers, such as their height, weight, and age," study author Louis Muglia, MD, PhD, co-director of the Perinatal Institute at Cincinnati Children's Hospital Medical Center, says. "We found when we ran our analysis that mom's height was a risk factor for having a preterm birth, so we decided to investigate this further."

Genentics

What the researchers discovered was surprising when they looked at the reasons behind this correlation. They found a genetic link between maternal height and a baby's birth weight and length. That was expected—small parents make small babies.

However, the pregnancy length was not simply caused by the mother's genetics, meaning something else was responsible for shorter people having shorter pregnancies.

Environment

Studies have found that while genetics are a significant component of determining height, environmental factors also play a role. For example, researchers have found that environmental factors in childhood known to affect growth include:

• Nutrition (particularly a lack of dietary protein)
• Childhood diseases and infections
• Parental education and income

Dr. Muglia says that whatever influences maternal height, such as genes, nutrition, and other health habits, influences how long someone will carry their pregnancy. He says researchers think this relationship may exist either because maternal height influences uterine size or pelvic size or height is related to their metabolism and how much energy they can supply to a growing baby prior to birth.

In other words, environmental factors influence maternal height, influencing how long a baby can stay put. Joe Leigh Simpson, MD, former March of Dimes senior vice president for Research and Global Programs (2012-2018), reiterates that gestational length is controlled by more than a person's genes. Whatever it was that makes someone short also generates a shorter gestational length.

Dr. Simpson says that, presumably, one's height reflected other things that had gone on in their lifetime—their nutritional status or exposure to pollution, for example.

What Can Short Pregnant People Do?

There's not much you can do to change your genetics. But if you're on the shorter side, can you do anything to make it to 40 weeks?

"I think height is just one of several factors that influence preterm birth risk," Dr. Muglia says. "Making sure to optimize other factors related to pregnancy health is key." He says these include the following:

• Being a healthy weight at the start of pregnancy
• Having appropriate pregnancy weight gain
• Not smoking
• Waiting an appropriate time between pregnancies (at least 18 months)

A health care provider may also want to monitor you a bit more closely if you're very petite. "When I saw patients, with someone who is 4 feet 10 inches tall, you intuitively know that this pregnancy may not last as long and there may be a need for a cesarean section because of the size of the pelvis," Dr. Simpson says. He especially keeps an eye on this if paternal height is a bit bigger and there's a risk for a bigger baby.

Nothing can be done about genetics, but environmental factors like poor nutrition, which often restricts people's growth in low-income countries, can be improved. Dr. Simpson says we know that many people in very unfavorable situations—stress, pollution, poor nutrition—still deliver at full term; they just have a higher risk of not making it to full term.

"Height is a part of the puzzle. But pregnancy is a very robust phenomenon. Otherwise, nobody who's short would ever have a full-term pregnancy!"