It is more conventional for women to gain weight during pregnancy, as their baby develops over the months. However, it is also quite normal to lose some weight, especially during the first trimester , as your body adjusts with all the changes related to pregnancy. Although common and often harmless, weight loss in early pregnancy is still not considered a sign that you are carrying.
Losing weight during the first trimester is commonly due to morning sickness  that often makes you too nauseated to have a normal appetite, preventing you from following the recommended diet. Severe morning sickness may lead to a condition called hyperemesis gravidarum (HG), another, more serious but rarer factor causing weight loss during this time .
The main reason behind gaining weight during pregnancy is to form a fat deposit for providing the energy required during labor, delivery and later for breastfeeding . For this reason, it is not unusual for obese women to lose some weight during this period as they already have sufficient amount of these energy resources in their body. If you are overweight and are unable to modify your diet, then the calories stored in your body will be utilized for your baby’s nutritional requirements, resulting in weight loss .
There is not much to worry about if you are losing a little weight early in the pregnancy. Most women gradually regain their appetite by the second trimester. However, you can take some of the following measures to manage nausea and improve your appetite to make sure your baby is not deprived of his necessary nutrients:
If you are already past the 13th-14th weeks and are equally put off by the smell of most things edible, there is nothing to worry about too much. You can just follow the same diet and supplements as the first trimester, and your baby will be fine .
It is never recommended to follow a weight loss diet when pregnant as this will prevent you from getting the essential vitamins and minerals including folic acid, iron, calcium, and magnesium. You are supposed to get around 2500 calories per day during pregnancy to ensure proper fetal growth , which might be a little difficult to get if you are dieting.
Malnutrition during these nine months can come in the way of proper development of your baby, also increasing the risks of various maternal complications [3, 10].
Although being overweight is associated with an increased risk of high blood pressure, gestational diabetes, and pre-eclampsia, dieting is not recommended even in obese women . Moreover, if you are overweight at the time of conceiving, losing a little weight over the pregnancy does not reduce these health risks much .
If you fail to gain the recommended weight by the third trimester, consult your doctor for a proper diet to help you gain the necessary pounds .
In case the severe morning sickness persists even in the late second trimester, or you continue to lose weight after the 25th week of pregnancy, it might indicate some underlying condition. Rapid weight loss or losing weight despite following a proper diet any time during these nine months may indicate serious complications like gestational diabetes . Hyperemesis gravidarum often needs medical attention .