Reversal of anovulation with clomifene (trade names including Clomid) has a relatively less but yet significant risk of multiple pregnancy. Delivery interval
A 15-year German study of 8,220 vaginally delivered twins (that is, 4,110 pregnancies) in Hesse yielded a mean delivery time interval of 13.5 minutes. The delivery interval between the twins was measured as follows:

Within 15 minutes: 75.8%
16–30 minutes: 16.4%
31–45 minutes: 4.3%
46–60 minutes: 1.7%
Over 60 minutes: 1.8% (72 instances)The study stated that the occurrence of complications "was found to be more likely with increasing twin-to-twin delivery time interval" and suggested that the interval be kept short, though it noted that the study did not examine causes of complications and did not control for factors such as the level of experience of the obstetrician, the wish of the women giving birth, or the "management strategies" of the procedure of delivering the second twin. There have also been cases in which twins are born a number of days apart. Possibly the worldwide record for the duration of the time gap between the first and the second delivery was the birth of twins 97 days apart in Cologne, Germany, the first of which was born on November 17, 2018. Complications during pregnancy
Vanishing twins
Researchers suspect that as many as 1 in 8 pregnancies start out as multiples, but only a single fetus is brought to full term, because the other fetus has died very early in the pregnancy and has not been detected or recorded.
: 334  It has been associated with acute liver damage.In 2008 the US label was updated with a warning concerning a risk of premature closure of the ductus arteriosus in pregnancy.In October 2020, the U.S. Food and Drug Administration (FDA) required the drug label to be updated for all nonsteroidal anti-inflammatory medications to describe the risk of kidney problems in unborn babies that result in low amniotic fluid. They recommend avoiding NSAIDs in pregnant women at 20 weeks or later in pregnancy. Overdose
Symptoms of overdosing include kidney failure, gastrointestinal problems, bleeding, rashes, confusion, hallucinations, vertigo, seizures, and loss of consciousness. It is treated with induction of vomiting, gastric lavage, bone char, and control of electrolytes and vital functions. Interactions
Interactions are broadly similar to those of other NSAIDs. Mefenamic acid interferes with the anti–blood clotting mechanism of Aspirin. It increases the blood thinning effects of warfarin and phenprocoumon because it displaces them from their plasma protein binding and increases their free concentrations in the bloodstream. It adds to the risk of gastrointestinal ulcera associated with corticosteroids and selective serotonin reuptake inhibitors. It can increase the risk for adverse effects of methotrexate and lithium by lowering their excretion via the kidneys. It can increase the kidney toxicity of ciclosporin and tacrolimus. Combination with antihypertensive drugs such as ACE inhibitors, sartans and diuretics can decrease their effectiveness as well as increase the risk for kidney toxicity.