According to the Chinese concept, the body has two opposing and complementary vital forces - yin (cold) and yang(hot) and our health is dependent on the proper balance of these forces. When a woman get pregnant and give birth, it affect the hot-cold balance of the body, in order to balance them, it is treated by adjusting the diet.
Cooling foods - most vege, certain furits (sugar cane, water melon, pineapple, papaya) , medicinal tea, some chinese herbs (american ginseng). Excessive consumption of cooling foods is believed to produce 'wind', numbness, muscle cramps, aching veins, dizziness, coughing. Cooling food are not totally forbidden during pregnancy, but are avoided because they are belived to cause cramps in the mother and weak unhealthy children or miscarriages.
Heating food - meat (beef, mutton), spices, some fruits (durian), some chinese herbs(korean ginseng), brandy, rice wine and chocolate. They are not advocated during pregnancy because they are said to produce stout babies and this makes labour difficult. Chinese take heating foods during pregnancy because they are good for the health.
Heating food strengthen the body but too much of it causes 'hot air', like dry throat, dry lips, fever, etc.
Rice, poutlry, pork and certain fish are neutral. Thus the method of cooking enhance or dimisnish the effect of the food. Steaming is cooling, frying the oil is heating. Flavouring agens like ginger, pepper, rice wine, sesame oil are added when cooking to reinforce the heating good.
Then there are other groups call 'itchy food'(crabs, cockles, cuttlefish, prawns), 'windy food' (young cocunut, mango, jackfruits), 'poisonous food' (cockerel, crab, cockles, cuttlefish, catfish and some fish). These are avoided during pregnancy and confinement period because they may cause bleeding, produce an itch or hamper wound healing.