Which of the following is an anti-emetic commonly used in midwifery practice?

Cyclizine is an effective anti-emetic that is commonly used in midwifery practice to manage nausea and vomiting, particularly in pregnant women. It belongs to the class of medications known as antihistamines, which help to prevent the action of histamine, a substance in the body that can trigger nausea and vomiting. By blocking these receptors, cyclizine alleviates symptoms associated with motion sickness, as well as nausea related to pregnancy and other conditions.

The other options listed are not suitable for the purpose of treating nausea and vomiting in the midwifery context. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) used primarily for pain relief and to reduce inflammation, but it does not have anti-emetic properties. Aspirin, while also an NSAID, is similarly ineffective for nausea and is typically avoided during pregnancy due to potential risks to the fetus. Metformin is an oral medication used primarily to manage type 2 diabetes; it does not serve the purpose of treating nausea or vomiting. Thus, cyclizine stands out as the appropriate choice in this context.