Ruth C. Fretts, MD

A When the latent phase reaches 18 hours in nulliparous women, the likelihood of successful vaginal delivery decreases markedly.

Expert Commentary

This paper explores 2 sides of the same question:

• When has an induction failed?
  
• Is there an optimal length of the latent phase where the vaginal delivery rate is high enough without placing the mother or baby in significant jeopardy?
  

This question is important because induction of nulliparous patients at or near term is a common obstetrical intervention, and because nulliparous women with an unfavorable cervix have a more protracted latent phase. The labor curve also differs between spontaneous and induced labors.

What constitutes a “failed” induction?

As the authors point out, we lack an exact definition. One group of researchers developed a definition based on outcomes.¹“In their frame-work,” Simon and Grobman note, “a failed induction of labor may be diagnosed in women whose continued lack of progression into the active phase makes it unlikely that they would safely proceed to a vaginal deliv-ery.” The investigators¹ opined that, in nulliparous gravidas, a latent phase of up to 12 hours was safe, while longer periods carried a low chance (13%) of vaginal delivery.

Simon and Grobman performed their study to “further determine the most clinically relevant definition of a failed induction of labor.”

Details of the study

This was a relatively small retrospective chart review of 397 nulliparous women who were induced for medical or elective reasons. Of these, 32% underwent prior cervical ripening with the use of an extraamniotic saline-infusion catheter for 6 hours. The latent phase began with the initiation of oxytocin and amniotomy and ended when either 4 cm cervical dilation and 80% effacement were achieved, or the cervix dilated to 5 cm regardless of effacement. Only 2% of women never achieved active labor prior to cesarean section, but the rate of cesarean delivery increased in near linear fashion with the lengthening of the latent phase. Nevertheless, 64% of women who had a latent phase up to 18 hours delivered vaginally. After 18 hours in the latent phase, the rate of vaginal delivery dropped such that the women who had a latent phase of 18.1 to 21 hours had a cesarean rate of 69%.

Other risks of a prolonged latent phase

Maternal hazards were an increased risk of chorioamnionitis and postpartum hemorrhage, though this did not translate into a lengthened hospital stay or increased transfusion rate. There was no appreciable neonatal consequence of a prolonged latent phase as measured by meconium, special care nursery admission, or umbilical cord pH.

Bottom line

This study provides some reassurance that, when the latent phase is 18 hours or less, patience may pay off with a vaginal delivery and acceptable maternal and neonatal risk. Keep in mind, however, that this study did not address the role of misoprostol for cervical ripening. Nor was it powered to assess the risk for relatively rare outcomes such as hysterectomy.

The commentators report no financial relationships relevant to these articles.

A When the latent phase reaches 18 hours in nulliparous women, the likelihood of successful vaginal delivery decreases markedly.

Expert Commentary

This paper explores 2 sides of the same question:

• When has an induction failed?
  
• Is there an optimal length of the latent phase where the vaginal delivery rate is high enough without placing the mother or baby in significant jeopardy?
  

This question is important because induction of nulliparous patients at or near term is a common obstetrical intervention, and because nulliparous women with an unfavorable cervix have a more protracted latent phase. The labor curve also differs between spontaneous and induced labors.

What constitutes a “failed” induction?

As the authors point out, we lack an exact definition. One group of researchers developed a definition based on outcomes.¹“In their frame-work,” Simon and Grobman note, “a failed induction of labor may be diagnosed in women whose continued lack of progression into the active phase makes it unlikely that they would safely proceed to a vaginal deliv-ery.” The investigators¹ opined that, in nulliparous gravidas, a latent phase of up to 12 hours was safe, while longer periods carried a low chance (13%) of vaginal delivery.

Simon and Grobman performed their study to “further determine the most clinically relevant definition of a failed induction of labor.”

Details of the study

This was a relatively small retrospective chart review of 397 nulliparous women who were induced for medical or elective reasons. Of these, 32% underwent prior cervical ripening with the use of an extraamniotic saline-infusion catheter for 6 hours. The latent phase began with the initiation of oxytocin and amniotomy and ended when either 4 cm cervical dilation and 80% effacement were achieved, or the cervix dilated to 5 cm regardless of effacement. Only 2% of women never achieved active labor prior to cesarean section, but the rate of cesarean delivery increased in near linear fashion with the lengthening of the latent phase. Nevertheless, 64% of women who had a latent phase up to 18 hours delivered vaginally. After 18 hours in the latent phase, the rate of vaginal delivery dropped such that the women who had a latent phase of 18.1 to 21 hours had a cesarean rate of 69%.

Other risks of a prolonged latent phase

Maternal hazards were an increased risk of chorioamnionitis and postpartum hemorrhage, though this did not translate into a lengthened hospital stay or increased transfusion rate. There was no appreciable neonatal consequence of a prolonged latent phase as measured by meconium, special care nursery admission, or umbilical cord pH.

Bottom line

This study provides some reassurance that, when the latent phase is 18 hours or less, patience may pay off with a vaginal delivery and acceptable maternal and neonatal risk. Keep in mind, however, that this study did not address the role of misoprostol for cervical ripening. Nor was it powered to assess the risk for relatively rare outcomes such as hysterectomy.

The commentators report no financial relationships relevant to these articles.

A When the latent phase reaches 18 hours in nulliparous women, the likelihood of successful vaginal delivery decreases markedly.

Expert Commentary

This paper explores 2 sides of the same question:

• When has an induction failed?
  
• Is there an optimal length of the latent phase where the vaginal delivery rate is high enough without placing the mother or baby in significant jeopardy?
  

This question is important because induction of nulliparous patients at or near term is a common obstetrical intervention, and because nulliparous women with an unfavorable cervix have a more protracted latent phase. The labor curve also differs between spontaneous and induced labors.

What constitutes a “failed” induction?

As the authors point out, we lack an exact definition. One group of researchers developed a definition based on outcomes.¹“In their frame-work,” Simon and Grobman note, “a failed induction of labor may be diagnosed in women whose continued lack of progression into the active phase makes it unlikely that they would safely proceed to a vaginal deliv-ery.” The investigators¹ opined that, in nulliparous gravidas, a latent phase of up to 12 hours was safe, while longer periods carried a low chance (13%) of vaginal delivery.

Simon and Grobman performed their study to “further determine the most clinically relevant definition of a failed induction of labor.”

Details of the study

This was a relatively small retrospective chart review of 397 nulliparous women who were induced for medical or elective reasons. Of these, 32% underwent prior cervical ripening with the use of an extraamniotic saline-infusion catheter for 6 hours. The latent phase began with the initiation of oxytocin and amniotomy and ended when either 4 cm cervical dilation and 80% effacement were achieved, or the cervix dilated to 5 cm regardless of effacement. Only 2% of women never achieved active labor prior to cesarean section, but the rate of cesarean delivery increased in near linear fashion with the lengthening of the latent phase. Nevertheless, 64% of women who had a latent phase up to 18 hours delivered vaginally. After 18 hours in the latent phase, the rate of vaginal delivery dropped such that the women who had a latent phase of 18.1 to 21 hours had a cesarean rate of 69%.

Other risks of a prolonged latent phase

Maternal hazards were an increased risk of chorioamnionitis and postpartum hemorrhage, though this did not translate into a lengthened hospital stay or increased transfusion rate. There was no appreciable neonatal consequence of a prolonged latent phase as measured by meconium, special care nursery admission, or umbilical cord pH.

Bottom line

This study provides some reassurance that, when the latent phase is 18 hours or less, patience may pay off with a vaginal delivery and acceptable maternal and neonatal risk. Keep in mind, however, that this study did not address the role of misoprostol for cervical ripening. Nor was it powered to assess the risk for relatively rare outcomes such as hysterectomy.

The commentators report no financial relationships relevant to these articles.

Objective

To study the fetal effects of excess maternal thyroid hormone (TH).

Results

Of the 36 couples in this study, 9 included women with TH resistance (RTH) who were euthyroid despite high TH levels, 9 included men with this condition, and 18 were unaffected. Mean miscarriage rates were 22.9%, 2.0%, and 4.4%, respectively. Infants without RTH who were born to mothers with the condition were significantly smaller than infants who shared their mother’s TH status.

Expert Commentary

Animal studies suggest that both hyperand hypothyroidism are associated with increased numbers of malformations and poor reproductive outcomes. In humans, hyperthyroidism is usually associated with thyroid autoantibodies, so it is unclear whether the increased rate of miscarriages seen with this condition is related to the elevated circulating thyroid hormone, to autoantibodies, or to both. To explore this, Anselmo et al took advantage of a “natural experiment” in a large extended family. This family harbored a single gene mutation, inherited autosomally, that made the TH receptor resistant to thyroid hormone.

Women with this mutation have, on average, twice the circulating TH level and normal thyroid-stimulating hormone (TSH). They are clinically euthyroid, without autoantibodies, but elevated TH levels pass to the fetus, which may or may not be genetically affected by the same condition.

Infants with mutation are protected

Anselmo et al found normal birth weight among babies affected by the same mutation as their mother. Presumably, these infants are euthyroid and grow normally despite elevated circulating TH. In contrast, infants who lack the mutation are significantly smaller due to the maternal environment of elevated circulating TH.

Unfortunately, although Anselmo and colleagues performed a thorough and thoughtful analysis, they did not indicate how prevalent this condition is in the general population.

Bottom Line

This study supports other evidence that elevated TH is associated with early fetal loss. This information can be generalized to patients with thyroid disease. Women on thyroid replacement should be monitored to ensure that their TH is in the normal range, and physicians should make every attempt to normalize TH in women with thyrotoxicosis.

Objective

To study the fetal effects of excess maternal thyroid hormone (TH).

Results

Of the 36 couples in this study, 9 included women with TH resistance (RTH) who were euthyroid despite high TH levels, 9 included men with this condition, and 18 were unaffected. Mean miscarriage rates were 22.9%, 2.0%, and 4.4%, respectively. Infants without RTH who were born to mothers with the condition were significantly smaller than infants who shared their mother’s TH status.

Expert Commentary

Animal studies suggest that both hyperand hypothyroidism are associated with increased numbers of malformations and poor reproductive outcomes. In humans, hyperthyroidism is usually associated with thyroid autoantibodies, so it is unclear whether the increased rate of miscarriages seen with this condition is related to the elevated circulating thyroid hormone, to autoantibodies, or to both. To explore this, Anselmo et al took advantage of a “natural experiment” in a large extended family. This family harbored a single gene mutation, inherited autosomally, that made the TH receptor resistant to thyroid hormone.

Women with this mutation have, on average, twice the circulating TH level and normal thyroid-stimulating hormone (TSH). They are clinically euthyroid, without autoantibodies, but elevated TH levels pass to the fetus, which may or may not be genetically affected by the same condition.

Infants with mutation are protected

Anselmo et al found normal birth weight among babies affected by the same mutation as their mother. Presumably, these infants are euthyroid and grow normally despite elevated circulating TH. In contrast, infants who lack the mutation are significantly smaller due to the maternal environment of elevated circulating TH.

Unfortunately, although Anselmo and colleagues performed a thorough and thoughtful analysis, they did not indicate how prevalent this condition is in the general population.

Bottom Line

This study supports other evidence that elevated TH is associated with early fetal loss. This information can be generalized to patients with thyroid disease. Women on thyroid replacement should be monitored to ensure that their TH is in the normal range, and physicians should make every attempt to normalize TH in women with thyrotoxicosis.

Objective

To study the fetal effects of excess maternal thyroid hormone (TH).

Results

Of the 36 couples in this study, 9 included women with TH resistance (RTH) who were euthyroid despite high TH levels, 9 included men with this condition, and 18 were unaffected. Mean miscarriage rates were 22.9%, 2.0%, and 4.4%, respectively. Infants without RTH who were born to mothers with the condition were significantly smaller than infants who shared their mother’s TH status.

Expert Commentary

Animal studies suggest that both hyperand hypothyroidism are associated with increased numbers of malformations and poor reproductive outcomes. In humans, hyperthyroidism is usually associated with thyroid autoantibodies, so it is unclear whether the increased rate of miscarriages seen with this condition is related to the elevated circulating thyroid hormone, to autoantibodies, or to both. To explore this, Anselmo et al took advantage of a “natural experiment” in a large extended family. This family harbored a single gene mutation, inherited autosomally, that made the TH receptor resistant to thyroid hormone.

Women with this mutation have, on average, twice the circulating TH level and normal thyroid-stimulating hormone (TSH). They are clinically euthyroid, without autoantibodies, but elevated TH levels pass to the fetus, which may or may not be genetically affected by the same condition.

Infants with mutation are protected

Anselmo et al found normal birth weight among babies affected by the same mutation as their mother. Presumably, these infants are euthyroid and grow normally despite elevated circulating TH. In contrast, infants who lack the mutation are significantly smaller due to the maternal environment of elevated circulating TH.

Unfortunately, although Anselmo and colleagues performed a thorough and thoughtful analysis, they did not indicate how prevalent this condition is in the general population.

Bottom Line

This study supports other evidence that elevated TH is associated with early fetal loss. This information can be generalized to patients with thyroid disease. Women on thyroid replacement should be monitored to ensure that their TH is in the normal range, and physicians should make every attempt to normalize TH in women with thyrotoxicosis.