Labor Induction and Fertility

Although many pregnancies progress normally beyond 40 weeks of gestation, the risks to both the mother and baby gradually increase with advancing gestational age. For this reason, labor induction is often considered between 40 and 42 weeks, particularly when additional risk factors are present.

Background

In the early nineteenth century, the German obstetrician Franz Carl Naegele developed a formula to estimate a woman's expected date of delivery (EDD). Known as Naegele's rule, the formula consists of subtracting three months from the first day of the last menstrual period (LMP) and then adding seven days. Using this method, pregnancy is estimated to last approximately 280 days, or 40 weeks, from the first day of the LMP.

Although Naegele's rule continues to be widely used, modern research has shown that first-trimester ultrasound is a more accurate method of estimating gestational age. Current studies show that ultrasound examinations performed between 9 and 11 weeks of gestation, which rely on crown-rump length measurements, can estimate gestational age within a few days. In fact, the American College of Obstetricians and Gynecologists (ACOG) states that:

“Ultrasound measurement of the embryo or fetus in the first trimester (up to and including 13 6/7 weeks of gestation) is the most accurate method to establish or confirm gestational age.”

Despite advances in ultrasound dating, considerable variation remains in the timing of spontaneous labor, and only a small percentage of women deliver on their estimated due date.

Introduction

Once the gestational age has been established, there is a period from 3 weeks before until 2 weeks after the estimated date of delivery – 40 weeks, which are considered normal. Until recently, a woman giving birth during that 5-week window was considered at “term”. However, this changed in 2013 when the ACOG replaced the single "term" label with more granular designations:

• Early term: 37 0/7 – 38 6/7 weeks

• Full term: 39 0/7 – 40 6/7 weeks

• Late term: 41 0/7 – 41 6/7 weeks

• Post term: ≥42 0/7 weeks

Although the revised gestational-age classifications were not introduced to promote labor induction, they coincided with a broader shift in obstetric practice that increasingly viewed 39 weeks as an optimal time for delivery. Within this context, the ARRIVE trial can be seen as part of a larger movement toward evaluating elective induction at 39 weeks.

According to a paper published in 2025 by Gynecology & Obstetrics, after the 2018 publication of the ARRIVE trial, elective induction rates increased by 42% almost immediately. By 2024, the U.S. labor induction rate had risen to 34.5% of all births — a 39% increase from 2016.

What happens during pregnancy

Labor begins through a complex cascade of hormonal changes involving both the mother and the fetus. Although the exact trigger for spontaneous labor is not fully understood, increasing fetal cortisol production, placental hormones, and mechanical stretching of the uterus all contribute to preparing the body for birth. As labor approaches, estrogen activity increases while the relaxing effects of progesterone diminish through a process known as functional progesterone withdrawal. At the same time, estrogen increases the number of oxytocin receptors in the uterine muscle, making the uterus highly responsive to oxytocin. Once labor begins, oxytocin stimulates uterine contractions, and the pressure of the baby's head against the cervix triggers the release of even more oxytocin. This positive feedback loop continues until the baby is born.

Pitocin and labor induction

Due dates are not exactly expiration dates. As seen above, there’s a 5-week window around the due date – 3 weeks before and 2 weeks after. As long as there are no medical concerns and the mother and baby are monitored regularly, the 5-week window applies. Trying to force labor simply because the baby is late could be contra productive.  Pitocin, a synthetic version of oxytocin, is commonly used to induce or augment labor, but its use is not without risks. Excessive uterine stimulation may result in overly frequent contractions, changes in fetal heart rate, and the need for additional medical interventions. In some cases, when induction is unsuccessful or fetal distress develops, cesarean delivery may be required. In addition, a study published in 2011 by the British Medical Journal concluded that the administration of oxytocin during labor increases the risk of postpartum hemorrhage, a major cause of maternal mortality and morbidity worldwide.

In an effort to protect the health of both the mother and the baby, there are circumstances in which labor induction is medically necessary. For example, induction may be indicated in pregnancies complicated by gestational diabetes, fetal growth restriction (low birth weight), oligohydramnios (low amniotic fluid), intrauterine infection, hypertensive disorders of pregnancy such as preeclampsia or gestational hypertension, chronic hypertension, placental abruption, or other conditions in which continuing the pregnancy poses a greater risk than delivery.

Stress and labor

The idea that fear and perceived danger can inhibit labor has been discussed for decades in obstetrics, midwifery, and physiology. One of the earliest and most influential work was published in 1968 by the American Journal of Obstetrics & Gynecology. The study titled “Effect of disturbance on labor” studied the effects of stress and fear on labor in both animals and humans during the 1940s–1960s. The researchers proposed that fear triggers the release of catecholamines (especially adrenaline), which can inhibit uterine contractions and interfere with labor progression. A decade later, another study concluded that higher levels of epinephrine were found to be associated with lower uterine contractile activity in the first stage of labor.

While stress hormones can interfere with labor by suppressing oxytocin release and reducing uterine efficiency, a calm and supportive environment may promote the natural hormonal processes involved in childbirth. A large Cochrane review found that continuous emotional and physical support during labor was associated with shorter labor duration, increased rates of spontaneous vaginal birth, and decreased rates of cesarean delivery, suggesting that a supportive birth environment may facilitate normal labor progression.

Acupuncture and labor preparation

Acupuncture, as shown by several studies, can reduce stress levels. As discussed earlier, elevated maternal stress during labor increases the release of hormones, such as cortisol, interfering with the body's natural production and action of oxytocin—the hormone responsible for uterine contractions. By promoting relaxation and reducing stress, acupuncture may help create a physiologic environment that supports the normal progression of labor.

A randomized study published in the American Journal of Obstetrics and Gynecology in 2024 investigated whether acupuncture administered before a scheduled induction could increase the likelihood of spontaneous labor. The authors found that women who received acupuncture four days before their scheduled induction were more likely to be admitted in spontaneous labor or after spontaneous rupture of membranes before their planned induction date.

Conclusion

Labor may slow or even temporarily stall when the mother experiences fear or stress. Physiologically, elevated stress hormones can interfere with the body's natural release and action of oxytocin, the hormone responsible for coordinated uterine contractions. Although labor induction is an essential and often lifesaving intervention in appropriately selected pregnancies, promoting the natural onset of labor whenever possible remains an important goal. Studies suggest that acupuncture may help reduce maternal stress and support the physiologic processes involved in spontaneous labor, making it a valuable complementary approach to labor preparation.