In a 33‑week‑gestation woman in active labor with a low‑lying fetal head and no other information, should we use forceps delivery, vacuum extraction (ventouse), cesarean section, or fetal scalp blood sampling?

Immediate Cesarean Section is Indicated

At 33 weeks gestation with the fetal head palpable in the vagina during labor, cesarean section is the only appropriate delivery method—operative vaginal delivery (forceps or vacuum) is absolutely contraindicated at this gestational age, and fetal scalp sampling does not address the need for immediate delivery. 1

Why Cesarean Section is Mandatory

Gestational Age Contraindications for Operative Vaginal Delivery

• Operative vaginal delivery (both forceps and vacuum extraction) requires term gestation (≥37 weeks) as a fundamental prerequisite. 1
• At 33 weeks, the preterm fetal skull is significantly more fragile and susceptible to intracranial hemorrhage, skull fractures, and severe neurologic injury from the compressive forces of forceps or vacuum application. 1
• The increased risk of maternal morbidity from second-stage cesarean delivery (including uterine extensions, hemorrhage, and infection) is still substantially lower than the catastrophic fetal risks of attempting operative vaginal delivery at 33 weeks. 1

Special Considerations for Impacted Fetal Head

• Given that the fetal head is already palpable in the vagina at 33 weeks (suggesting deep engagement), there is significant risk of impacted fetal head during cesarean delivery. 2, 3
• The surgical team should be prepared to use specialized disimpaction techniques including manual vaginal disimpaction (vaginal push method), uterine relaxation with tocolysis, or reverse breech extraction if standard delivery maneuvers fail. 2
• The Fetal Pillow device can be considered for prophylactic elevation of the fetal head before uterine incision to reduce impaction risk, though evidence for improved outcomes is mixed. 2

Why Other Options Are Inappropriate

Forceps and Vacuum Extraction

• Both instruments carry unacceptable risks of femoral and humeral fractures, intracranial hemorrhage, and permanent neurologic injury when applied to a preterm fetus at 33 weeks. 1
• The preterm skull lacks the structural integrity to withstand the traction and rotational forces inherent in operative vaginal delivery. 1

Fetal Scalp Blood Sampling

• Fetal scalp sampling is a diagnostic tool for assessing fetal acid-base status in cases of Category II fetal heart rate patterns, not a delivery method. 1
• This patient requires expedited delivery, not further diagnostic testing—the clinical scenario describes active preterm labor requiring immediate intervention. 1

Critical Pitfalls to Avoid

• Do not attempt operative vaginal delivery simply because the head is low and accessible—gestational age is an absolute contraindication regardless of station. 1
• Ensure the surgical team is prepared for potential impacted fetal head complications, as the deeply engaged head at 33 weeks may be difficult to elevate through the uterine incision. 2, 3
• Have tocolytic agents immediately available in the operating room for uterine relaxation if disimpaction maneuvers are required. 2