The early symptoms of twin pregnancy are similar to those of singleton pregnancy, but because of the greater changes in the levels of hormones such as HCG (human chorionic gonadotropin), estrogen and progesterone in twin mothers, the reaction of twins is greater than that of singletons and appears earlier, such as menopause, early pregnancy reaction, breast tenderness, frequent urination, etc., especially the swelling and soreness of the lower back and abdomen, physical discomfort such as easy exertion and early pregnancy reaction such as nausea and vomiting. 1. The swelling and soreness of the lower back and abdomen appear earlier in the early stage of twin pregnancy, which is a physical discomfort caused by pregnancy and is a normal physiological phenomenon during pregnancy, due to early embryonic implantation, uterine ligament pulling, and changes in hormone levels in the body resulting in accelerated metabolism in the body. Pregnant mothers are prone to back pain and strain after regular activities, which can be relieved after rest. 2, twin pregnancy due to changes in the mother’s body hormone level can appear early pregnancy reaction, such as cold, dizziness, limb weakness, drowsiness, nausea and vomiting, hate greasy, like to eat sour food, etc.. The nausea and vomiting reactions in twin pregnancies are large, appear early and last for a long time until the middle of pregnancy or even the whole pregnancy (in singleton pregnancies, they mostly appear around 6 weeks after menopause and disappear on their own around 12 weeks), and some twin pregnant mothers are unable to eat and water due to heavy nausea and vomiting reactions, resulting in severe pregnancy vomiting, which endangers the health of the mother and fetus (in serious cases, the fetus develops miscarriage, Wernicke syndrome and ketoacidosis in pregnant mothers). Clinically, the symptoms of the first month of pregnancy are usually not obvious, and doctors mainly rely on blood and urine HCG and vaginal ultrasound to clarify the pregnancy and the size of the gestational week; while the diagnosis of twin pregnancies and the confirmation of chorionicity need to be obtained by ultrasound examination at 6-14 weeks of pregnancy. Chorionicity, related to whether the 2 fetuses live in one amniotic cavity and share one placenta, is divided into dichorionic twin amniotic twins (living in different amniotic cavities with their own placentas, either identical or heterozygous), monochorionic twin amniotic twins (living in different amniotic cavities and sharing one placenta), and monochorionic monoamniotic twins (living in one amniotic cavity and sharing one placenta).