When should labor be induced in a pregnant patient, particularly those with a history of hypertension?

When to Induce Labor

For low-risk nulliparous women, elective induction at 39 weeks 0 days gestation is reasonable and reduces cesarean delivery rates and hypertensive disorders without increasing perinatal morbidity. For women with gestational hypertension, induction should occur at 37 weeks 0 days gestation to prevent progression to preeclampsia and severe hypertensive disease. 1, 2

Low-Risk Nulliparous Women (No Hypertension)

Timing and Eligibility

• Offer elective induction at 39 weeks 0 days gestation to low-risk nulliparous women who meet ARRIVE trial eligibility criteria 1
• Women must have reliable pregnancy dating confirmed by early ultrasonography before 21 weeks gestation (or first-trimester ultrasound if uncertain last menstrual period) 2
• Eligibility requires no obstetric or medical complications, regardless of cervical favorability 1

Maternal Benefits at 39 Weeks

• Cesarean delivery rate decreases from 22.2% to 18.6% (RR 0.84), requiring 28 inductions to prevent one cesarean 1
• Hypertensive disorders (preeclampsia and gestational hypertension) decrease from 14.1% to 9.1% (RR 0.64) 1, 2
• No statistically significant difference in perinatal death or severe neonatal morbidity between induction and expectant management 1

Shared Decision-Making

• Both elective induction at 39 weeks and expectant management are reasonable options 1
• Some women will prefer the reduced cesarean and hypertension risk with induction; others will prefer awaiting spontaneous labor 1
• Do not offer elective induction under circumstances inconsistent with ARRIVE protocol unless part of research or quality improvement 1

Women with Gestational Hypertension

Timing of Delivery

• Induce labor at 37 weeks 0 days gestation for women with gestational hypertension (new-onset hypertension ≥140/90 mmHg after 20 weeks without proteinuria) 2
• This timing reduces maternal complications, particularly progression to preeclampsia and severe hypertensive disease, without increasing cesarean delivery rates 2
• Most international guidelines aligned with ACOG principles recommend delivery at exactly 37 weeks for gestational hypertension 2

Alternative Timing Options

• Some guidelines support discussing delivery from 37-39 weeks, allowing shared decision-making 2
• Three guidelines recommend delivery between 38-39 weeks as an alternative approach 2

Prerequisites for Safe Induction

• Gestational age must be confirmed by early ultrasonography - this is the most critical safety measure 2
• For women certain of last menstrual period, dating ultrasound must be performed before 21 weeks 2
• For uncertain last menstrual period, only first-trimester ultrasound dating is acceptable 2
• Never offer elective induction without confirmed early ultrasound dating 2

Medical Indications for Induction (Any Gestational Age)

Clear Medical Indications

• Rh problems, maternal diabetes, preeclampsia at or near term when delivery is in the best interest of mother and fetus 3
• Premature rupture of membranes with indication for delivery 3
• Uterine inertia requiring stimulation or reinforcement of labor 3
• Postpartum hemorrhage control (third stage of labor) 3

Timing Based on Condition

• Women with medical or obstetric conditions necessitating induction should be delivered at a time consistent with standard recommendations for each specific condition 1
• Spontaneous onset of labor is appropriate and preferable for women with normal cardiac function and most heart disease 1

Cervical Ripening Considerations

Unfavorable Cervix (Modified Bishop Score <5)

• Most women (63%) in the ARRIVE trial had unfavorable cervices at randomization 1
• Cervical ripening agent should be used for women with unfavorable cervix 1
• Allow at least 12 hours after completion of cervical ripening, rupture of membranes, and uterine stimulant use before considering cesarean for "failed" induction in latent phase 1

Favorable Cervix

• Combined amniotomy and intravenous oxytocin is generally the most effective approach for women with favorable cervix 4

Mechanical vs Pharmacologic Methods

• For women with cardiovascular disease, mechanical methods (Foley catheter) are preferable to pharmacological agents, particularly in patients with cyanosis where drop in systemic vascular resistance would be detrimental 1
• Dinoprostone has profound effects on blood pressure and is contraindicated in active cardiovascular disease 1
• Misoprostol carries theoretical risk of coronary vasospasm and low risk of arrhythmias 1

Critical Pitfalls to Avoid

Dating and Eligibility Errors

• Never rely on last menstrual period alone for dating - early ultrasound confirmation is mandatory 2
• Do not offer elective induction without confirmed early ultrasound dating 2
• Ensure adequate labor and delivery capacity before implementing routine early term induction 2

Severe Hypertension Management

• Do not withhold antihypertensive therapy if blood pressure reaches severe range (≥160/110 mmHg sustained >15 minutes) 2
• Severe hypertension requires immediate treatment and consideration for delivery 2
• First-line agents include IV labetalol, oral nifedipine, or IV hydralazine 2

Postpartum Monitoring

• Blood pressure typically rises in first 3-6 days postpartum - hypertension may worsen or appear de novo after delivery 2, 5
• Do not discharge patients with preeclampsia without clear blood pressure monitoring plan for critical first 3-7 days 5
• Switch methyldopa to alternative agents postpartum due to risk of postpartum depression 2, 5

Contraindications to Induction

Absolute Contraindications

• Prematurity, borderline cephalopelvic disproportion, previous major surgery on cervix or uterus including cesarean section 3
• Overdistention of uterus, grand multiparity, invasive cervical carcinoma 3
• Patients on oral anticoagulants may require cesarean delivery to minimize period off anticoagulation 1

Monitoring Requirements

• All patients receiving intravenous oxytocin must be under continuous observation by trained personnel 3
• Physician qualified to manage complications must be immediately available 3
• Overstimulation can be hazardous to both mother and fetus even with proper administration 3

Special Populations

Multiparous Women

• Unknown whether ARRIVE findings can be extrapolated to multiparous women 1
• Further research needed to measure impact in settings other than clinical trial 1

Cardiac Disease

• Vaginal delivery is preferred mode for most women with heart disease 1
• Cesarean delivery reserved for obstetric indications or specific cardiac conditions (significant aortopathy, severe pulmonary hypertension, ongoing anticoagulation requirement) 1
• Induction should be considered at 40 weeks gestation for all women with cardiac disease 1