For most pregnant women, nausea and vomiting are most likely to develop in the first month or two of pregnancy and start tapering off by the end of the first trimester-by week 18 at the outside. But as many as 20 percent of women may find that their symptoms of pregnancy nausea lasting into the third trimester, and 5 percent experience nausea and vomiting right up to delivery.
For some women, morning sickness stops after a few weeks at the start of their pregnancy, only to return again around week 27 or after. Still other women have no nausea at all in early stages, and are quite surprised to find it developing in the last three months.
Of course, at any time, a sudden onset of nausea and vomiting can be due to a virus or other illness. Especially if it is accompanied by diarrhea, it could be the flu or food poisoning. If such symptoms are severe at any time during pregnancy, it's important to be wary of dehydration and make sure to replenish the fluids being lost.
Starting around week 27, hormone activity tends to pick up again, after having leveled off somewhat for most women during the mid-stages of pregnancy. Women who maintain high levels of the hCG hormone are particularly likely to find that their NVP also continues throughout pregnancy.
Another instigator of nausea and vomiting the later stages of pregnancy is simply the size of the growing fetus. At this time it's most common for nausea to strike immediately after a meal, often accompanied by heartburn. As the baby gets bigger, the uterus exerts more pressure on the stomach causing heartburn and nausea when the stomach is filled. At this point, stomach capacity is even smaller, and it's even more important to stick to smaller meals to reduce this stress.
So nausea in the third trimester isn't necessarily unusual or worrisome. However, there are a couple of serious late-pregnancy liver diseases that can also lead to nausea and vomiting, including acute fatty liver of pregnancy and HELLP syndrome. Though both of these ailments are truly rare, they are also life-threatening if untreated. For this reason, doctors now recommend that any woman experiencing nausea and vomiting accompanied by upper abdominal pain and "malaise" in the third trimester of pregnancy have her liver enzymes and renal function evaluated, along with a complete blood count.
Also, any woman who is experiencing nausea and vomiting in combination with severe headaches, facial swelling, sudden swelling, abdominal pain, and visual disturbances (e.g., seeing spots) should call her physician immediately. These are signs of preeclampsia, an illness that can develop quite rapidly anytime after the 20th week of pregnancy and that affects as many as 8 percent of pregnancies. Preeclampsia can cause strokes and kidney damage, liver failure, blot clots, fluid in the lungs, seizures, and even death of both the child and the mother.
There is one final factor that can lead to nausea in late pregnancy-though in this instance it is a bit easier to diagnose. If nausea, vomiting and diarrhea coincide with cramps, backache, pelvic pressure, and contractions occurring less than 10 minutes apart, labor has begun.
While not uncommon, then, nausea late in any pregnancy merits a consultation with your care provider. In most cases there are ordinary and harmless reasons for it, but there is an outside chance that is a symptom of one of these several serious illnesses that occasionally arise during the late weeks of pregnancy.