Dr. Sparks blogs about “Why 39 Weeks?”

Consider a common situation. After a long and uncomfortable pregnancy, an expectant mother asks her doctor if she can choose a date for her delivery.  She has considered her family’s complicated schedule including childcare issues, her work situation, her husband’s work schedule, and the availability of grandparents to visit and provide support. She might mention holidays or competing birthdays of other family members. (Not unusual—my wife and I did not want our daughter’s birthday to be Halloween). For discussion, let’s say she tells her doctor that “Friday” would be the ideal day for her baby’s birth.

Her obstetrician tells her that she will not be 39 weeks until Sunday, making Monday the earliest option for her delivery. She feels frustrated that her doctor does not understand how this small difference would complicate her life—that there seems to be no flexibility in her doctor’s decision.

Until recently, few expectant parents got to “choose” a delivery date. Most babies were born after labor began spontaneously. Relatively few exceptions were generally related to medical complications that made delivery safer for mother and/or baby than continuation of the pregnancy. This is still true for the majority of pregnancies. But today, more women are asked “What day would you prefer for your delivery?”

Scheduled deliveries are more common today for a number of reasons. There are more cesarean deliveries, fewer vaginal births after cesarean delivery, and more elective inductions (labor induced for a non-medical reason). Each of these deserves to be the topic of a future blog post. But for now, let’s focus on why obstetricians have become so inflexible about offering a delivery date before the end of 39 weeks of gestation (pregnancy).

The timing of a scheduled elective delivery depends on your baby’s gestational age (age before birth) and the risk of prematurity. It is important to understand that gestational age is usually just an estimate and the risk of prematurity is a variable term. We count “gestational age” as the number of days or weeks from the first day of the last menstrual period (LMP). We assume that ovulation and conception occurred 14 days after that date. Since menstrual cycles vary and ovulation delay is possible, the baby’s exact gestational age is only known in cases of in vitro fertilization or when ovulation was documented using biochemical testing. The day we estimate as your “due date” (EDD) is assigned as 40 weeks from your LMP date.  Normal should be viewed as delivery around that imprecise date. In fact, around 80% of babies arrive sometime between 2-weeks before and 2-weeks after your EDD.

A baby’s ability to survive the transition to life outside the uterus improves with gestational age. Before 24 weeks, chance for a healthy life is near zero. For “term” infants the risk of serious complications or death is very low. Keeping that maturation difference in mind, we have—for many years—used 38 weeks as a guideline when advising our patients about an elective delivery.

Recently, however, medical studies have given us new information. The newest data show a statistical difference in the health of infants born at 39 weeks, compared with those born at 38 weeks. For that reason, guidelines have changed nationally. Since that small change, significantly fewer babies are being admitted to newborn intensive care units (NICU)—indicating healthier newborns.  Most hospitals, including Brookwood, now require obstetricians to document a medical reason (a complication for mother or baby that makes early delivery necessary) if we schedule a delivery before 39 weeks.

Back to the beginning, if you are anticipating a schduled delivery, we want to help you choose a “family friendly” date. For you and your doctor, your baby’s health will always be the top priority. Remember, Healthy Babies Need 39 Weeks!