Does Height Impact Gestation Length?

Every mom-to-be will be peppered with the same question for nine months straight, “When are you due?” With less than 5% of babies being born on their actual due date, a baby’s birthday is anyone’s guess. New research performed by The March of Dimes offers a hint into just how long an expecting mother, or her surrogate, may be waiting to give birth.

Common knowledge tells us that the typical human gestation period is 38-42 full weeks, just about nine months. But these new findings are challenging this long accepted fact and suggesting that a woman’s height may play a role in the length of her period. Simply stated; shorter women have shorter pregnancies.

In a 2015 study released by the March of Dimes, researchers found that shorter women tend to have shorter pregnancies. The study also suggested that they tend to have an elevated risk for birthing smaller babies and pre-term deliveries.

No need for concern from intended parents with shorter surrogates though, as the study showed that maternal height, which is established by genetic factors, is directly responsible for the length of the gestation. This means that a surrogate’s height plays no role in cases of shorter-term pregnancies or prematurity, since she shares no genetic link with the child she is carrying.

The study went on to conclude that while maternal height does play a role in the length of the pregnancy, there is no determinate connection between the genetic influence of the biological mother and the birth weight or length of the child. Those traits tend to be influenced by other transmitted genes.

For now, researchers say that they can’t explain the cause for the link between maternal height and gestational length, suggesting only that lifetime factors such as nutrition, environment, and unknown genetic considerations may play a role. In the case of surrogacy, this could explain why a surrogate’s personal pregnancy lengths can vary from the pregnancy length she experiences as a surrogate.

Read more about the study here.

Kim Bergman, PhD, a licensed psychologist of 26 years, has specialized in the area of gay and lesbian parenting, parenting by choice and third party assisted reproduction for over two decades. Dr. Bergman has created a comprehensive psychological screening, support and monitoring process for intended parents, surrogates and donors. She is the co-owner of Growing Generations and is a member of the American Society for Reproductive Medicine, the American Psychological Association, the Los Angeles County Psychological Association, the Lesbian and Gay Psychotherapy Association, and the Gay and Lesbian Medical Association. She is on the national Emeritus board of the Family Equality Council. Dr. Bergman writes, teaches and speaks extensively on parenting by choice. Along with co-authors, she published “Gay Men Who Become Fathers via Surrogacy: The Transition to Parenthood” (Journal of GLBT Family Studies, April 2010). Dr. Bergman’s is the author of the book, Your Future Family: The Essential Guide to Assisted Reproduction (Conari Press 2019) as well as the children's book You Began as a Wish (Independent Press 2019). Dr. Bergman created her own family using third party assisted reproduction and she lives with her wife of 35 years. She has two adult daughters.