Several categories of drugs may be used during labor, depending on the situation: pain relief medications, drugs to start or strengthen contractions, antibiotics to prevent infection, and medications to manage complications like high blood pressure or heavy bleeding. Not every laboring person receives all of these, and the specific combination depends on how labor unfolds.
Epidural and Spinal Pain Relief
The epidural is the most well-known form of labor pain relief and the most effective. It involves placing a thin catheter into the space just outside the spinal cord, through which a continuous flow of medication numbs the lower body. The drugs used are a local anesthetic (most commonly bupivacaine or ropivacaine in North America) combined with a small dose of a strong pain reliever like fentanyl. The local anesthetic blocks nerve signals from the uterus and birth canal, while the fentanyl boosts the pain relief so that lower doses of each drug can be used.
At today’s standard low concentrations, these medications don’t slow down labor or cause breathing problems in the newborn. A combined spinal-epidural is a variation where a single small dose is injected closer to the spinal cord for fast-acting relief, and then the epidural catheter is placed for ongoing medication. You typically feel pressure and movement but not sharp pain, and you can still shift positions in bed.
IV and Inhaled Pain Relief
If you want something less intensive than an epidural, or you need relief quickly before an epidural can be placed, intravenous opioids are an option. These are injected into your IV line and take effect within minutes. They provide sedation and relaxation more than true pain relief. Strong evidence suggests that IV opioids don’t actually reduce the intensity of labor pain the way regional anesthesia does, though many people find the relaxation helpful.
The main concern with IV opioids is their effect on the baby. If given too close to delivery, opioids can cross the placenta and affect the newborn’s breathing, causing pauses in breathing, irregular breathing patterns, and a weakened response to low oxygen levels. For this reason, the timing of these medications relative to delivery matters.
Nitrous oxide is another option that has grown in popularity in the U.S. since the first FDA-approved delivery system became available in 2011. It’s a 50/50 mix of nitrous oxide and oxygen, delivered through a handheld mask that you hold yourself (no straps, so if you become too drowsy, the mask falls away as a built-in safety feature). Because it takes about 30 to 50 seconds to kick in, you start breathing it just before a contraction begins so the peak effect lines up with the peak of pain. It’s milder than an epidural and won’t eliminate pain, but it takes the edge off and can reduce anxiety. It clears your system quickly between contractions.
Drugs to Start or Speed Up Labor
When labor needs to be induced or isn’t progressing on its own, two main types of medication are used. Prostaglandins are given first when the cervix isn’t yet soft and open enough for labor to begin. These come in several forms: a slow-release vaginal insert (dinoprostone), a vaginal gel, or an oral tablet (misoprostol, typically a 25-microgram dose). Their job is to soften and thin the cervix, a process called ripening, which can take many hours.
Once the cervix is favorable, or if contractions need to be strengthened, synthetic oxytocin (commonly known by the brand name Pitocin) is given through an IV. The dose starts low and is gradually increased until contractions are regular and strong. Oxytocin is one of the most commonly administered drugs in labor overall, used for both induction and augmentation of stalled labor.
Antibiotics for Group B Strep
About 1 in 4 pregnant people carry Group B Streptococcus (GBS) bacteria, which is harmless to adults but can cause serious infection in newborns during delivery. If you tested positive for GBS during pregnancy (usually screened between 36 and 37 weeks), you’ll receive IV antibiotics during labor.
The preferred antibiotic is penicillin G, given as an initial dose followed by additional doses every four hours until delivery. Ampicillin is an acceptable alternative, though penicillin is favored because its narrower action is less likely to promote antibiotic resistance. If you’re allergic to penicillin, clindamycin or erythromycin are used instead. The goal is to have at least one full dose in your system for a minimum of four hours before birth to give the baby adequate protection.
Magnesium Sulfate for Preeclampsia
If you have preeclampsia (dangerously high blood pressure during pregnancy), magnesium sulfate is given through an IV to prevent seizures. The standard approach is a loading dose of 4 to 6 grams, followed by a continuous infusion of 2 grams per hour. A 6-gram loading dose is more reliably effective at reaching protective blood levels within two hours compared to the 4-gram dose. This medication typically continues through labor and for 24 hours after delivery.
Magnesium sulfate can cause flushing, warmth, nausea, and a heavy or drowsy feeling. Your team will monitor your reflexes and blood levels throughout to make sure the dose stays in the therapeutic range.
Local Anesthetics for Tears and Repairs
If you tear during delivery or need an episiotomy repaired, a local anesthetic like lidocaine or mepivacaine is injected directly into the tissue to numb the area for stitching. This is a small injection at the site and works within seconds. If you already have an epidural that’s still active, you may not need additional local anesthesia for the repair.
Medications to Prevent Heavy Bleeding
Immediately after delivery of the placenta, you’ll receive a uterotonic, a drug that causes the uterus to contract firmly and clamp down on the blood vessels where the placenta was attached. This is standard practice for every delivery because it significantly reduces the risk of postpartum hemorrhage.
The World Health Organization recommends 10 international units of oxytocin (the same drug used to induce labor, now given as a single dose) as the first-line treatment. In situations where the bleeding risk is higher, combinations are more effective. Oxytocin paired with misoprostol reduces the risk of significant blood loss by about 30% compared to oxytocin alone, and the combination of oxytocin with ergometrine reduces it by about 24%. Carbetocin, a longer-acting version of oxytocin, performs similarly to standard oxytocin and tends to cause fewer side effects.
The trade-off with combination treatments is more side effects. Misoprostol can cause nausea, vomiting, diarrhea, and fever. Ergometrine tends to cause nausea and vomiting and can raise blood pressure, so it’s avoided in people with hypertension. Oxytocin alone has the mildest side effect profile, which is one reason it remains the standard first choice for most deliveries.