Most women give birth spontaneously, but some need assistance during the second stage of labour with instruments such as obstetric forceps or vacuum, especially in the case of obstructed or prolonged labor. A Cochrane review found that overall, forceps or metal cup appear to be the most effective at achieving a vaginal birth, but with increased risk of maternal trauma with forceps and neonatal trauma with the metal cup. Over the past two decades authorities have declared vacuum extraction the method of choice in modern obstetric practice due to improved safety for the fetus and less likelihood of maternal morbidity. The risks of failed delivery and trade-offs between risks of maternal and neonatal trauma thus need to be considered when choosing an instrument.
In the event that labor cannot be resolved by manipulation (to reposition the fetus) or instrumentation, Caesarean section may be required. Caesarean section (C-section) is a common abdominal operation for surgical delivery of a baby and the placenta, with techniques varying depending on the clinical situation and surgeon preferences. However, C-sections require effective anesthesia which can be regional (epidural or spinal) or a general anesthetic.
The rates of instrumental vaginal births range from 5% to 20% of births in high-income countries, with less information about the incidence in low-income countries. In general, assisted vaginal delivery (AVD) is more common in high-income countries than in low- and middle-income countries (LMICs). A limited review of EmOC signal functions in 2006 found that AVD was generally the signal function least likely to have been performed. Other studies in sub-Saharan Africa also find that AVD was the signal function most often missing in health facilities.[7,8] In Latin America, availability of AVD may be even lower - previous studies reported it to be completely missing for facilities in Nicaragua, and uncommon in Peru and no longer part of the pre-service training curriculum at some of the country’s leading medical schools. A review of AVD found that it is more likely to be performed in hospitals than in health centres and clinics, and the top reported reason for non-performance was equipment-related, followed by lack of staff training. Most countries surveyed appeared to show a preference for vacuum extraction over forceps, especially at non-hospitals, which may reflect the global transition in instrument choice and a consensus that forceps is more difficult to use and less versatile.
We identified multiple studies that examined the efficacy of treating obstructed labor on reducing maternal mortality rates.[11,12,13,14] The efficacy of assisted delivery for obstructed labor is high - for example, Yarrow 2004 reported a 94.1% success rate when using vacuum-assisted deliveries, and of the nine failed vacuum deliveries, four were subsequently delivered by forceps and five by cesarean section, with no maternal mortality reported. AVD is thus sometimes first attempted, with a c-section performed if needed. A multi-country study in sub-Saharan Africa found that obstructed labor accounted for 31.3% of all c-sections, followed by malpresentation (18.3%). A WHO Global survey in 2004-2008 found that operative vaginal deliveries accounted for only 2.6% of deliveries, compared to nearly 25% of deliveries by c-section with indications, suggesting that c-sections are far more commonly used than AVD. We include these estimates of operative vaginal deliveries as calibration targets in the model.
For women with obstructed labour, we model the availability and efficacy of assisted delivery, conditional on delivery site. We assume that the availability of treatment increases by site and income group, and that treatment is not available at home. We assume that treatment availability increases over time and so constrain the year coefficient to be non-negative when sampling. We assume that ‘severe’ OL requires c-section and can only be treated at CEmOC facilities, while ‘moderate’ OL can be treated with AVD if available. However, given the preference for c-section over AVD in many cases, we simulate a probability of c-section instead of AVD for women with moderate OL at EmOC as well. We assume that the efficacy of treatment is non-differential by severity (moderate/severe) or mode (AVD/c-section), and apply the same risk reduction for all mortality and morbidity outcomes. We set priors centered around 95% efficacy for risk reduction based on the empirical data.
Conditional on the delivery site we simulate the probabilities that treatment will be available and the efficacy of treatment on obstructed labour outcomes, accounting for quality of care.
GMatH (Global Maternal Health) Model - Last updated: 28 November 2022
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