Associate Professor Steve Robson explains why women can experience nausea and vomiting late in their pregnancy, and what to do when this occurs.
Most women will experience nausea, and possibly vomiting (commonly referred to as 'morning sickness') in early pregnancy. For the unlucky few, these unpleasant symptoms will persist beyond the first trimester. While 'nausea and vomiting of pregnancy' (NVP) is common and distressing, the severe condition called hyperemesis gravidarum is fortunately rare.
For the unlucky few who suffer unremitting morning sickness through to the latter stages of pregnancy, the condition can be exhausting and debilitating. And then there are some women who have a complete recovery, and assume they are in the clear, only to have the problems return towards the end of pregnancy.
There are a number of reasons why this can occur. As the uterus increases in size, the other abdominal organs (the bowel, in particular) are compressed in the upper part of the abdomen, against the diaphragm. Also, the hormones of pregnancy have some important effects. These hormones act to relax the valve, or 'sphincter,' that normally holds the junction between the oesophagus (gullet) and stomach closed. At the same time, the movement of food onward from the stomach into the small bowel can be very slow, a condition known as 'gastroparesis.' This means that there can be a lot of food in the stomach and this is pressed from below by the pregnant uterus. Due to the laxity of the sphincter, the food flows back upwards, and sometimes out. This can cause painful heartburn, nausea, and sometimes vomiting.
This can be relieved by simple measures such as eating smaller meals, avoiding lots of fluid with meals, taking antacids, and not eating too close to bedtime so women are not lying flat in bed with a full stomach. Some women sleep with their head elevated to help reduce the reflux. In severe cases, for which these measures do not provide relief, doctors sometimes prescribe medication that reduces acidity in the stomach and increases the movement of the stomach to help empty it. Fortunately, these symptoms usually resolve as soon as the baby is born.
There are some other important conditions that can cause nausea and vomiting in late pregnancy, and if you are in any doubt about what is causing it, make sure you contact your doctor or midwife. Food poisoning, for example with salmonella or E coli, can cause a sudden onset of vomiting, but usually with diarrhoea as well. Similarly, contagious episodes of gastroenteritis (such as caused by Norovirus) can also make women ill. Vomiting and diarrhoea can last for several days, leading to dehydration, and these can pose risks for both mother and baby, including miscarriage. For these reasons, it is important to be very conscious of food safety, and to avoid other people if an epidemic of gastroenteritis is occurring.
Finally, some important complications of pregnancy can sometimes lead to the onset of upper abdominal pain, nausea and vomiting. Fortunately, they are very rare, but women should always alert their doctor or midwife if they have concerns. Pre-eclampsia, a condition most commonly occurring in a woman's first pregnancy, can cause high blood pressure, swelling, and the presence of protein in the urine. In very severe cases, it can cause a woman to feel acutely unwell, with pain in the upper abdomen, nausea and vomiting. The other condition is acute fatty liver, which is extremely rare and can be difficult to diagnose as sometimes the initial signs are very vague. Acute fatty liver can be so severe it can lead to loss of the baby, and sometimes a liver transplant is the only treatment – thankfully we rarely see this.
In summary, women who have nausea and vomiting in the third trimester will often feel better with simple measures. If the condition doesn't respond, becomes severe, or is associated with other problems, make sure you let your doctor or midwife know straight away.
Associate Professor Steve Robson is vice-president of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists and a practising obstetrician.