Some of our patients often ask, “Doctor, is IVF an option for twins?” Under the existing family planning policy in China, many couples who need IVF want to have two babies at once. In their minds, having twins means having two healthy babies in the future. In fact, we need to choose twin pregnancy carefully and understand the risks of twin pregnancy. We have encountered many clinical cases of adverse pregnancy outcomes after twin pregnancies. A couple who had been infertile for many years and had failed many in vitro fertilization attempts had a successful twin pregnancy in our hospital. There are also many pregnant women who suffer unavoidable miscarriages in the middle of pregnancy due to twin pregnancies and end up with pain and disappointment after months of hard work. Many twin babies are born prematurely, with low birth weight and growth retardation, which puts an even greater financial burden on the families who have already spent a lot. A multiple pregnancy is a pregnancy with two or more fetuses at the same time. The incidence of twin pregnancy is the highest, and there are two types of twin pregnancy: monozygotic (monozygotic) and dizygotic (dizygotic) twins. In recent years, with the introduction of ovulation-promoting drugs and assisted reproductive techniques such as intrauterine insemination, in vitro fertilization-embryo transfer, intra-ovarian microinjection of single sperm and assisted hatching, and blastocyst culture, the incidence of multiple pregnancies has increased significantly over the past 30 years. Currently, the overall multiple pregnancy rate in our center is about 30-40%, and the rate is even higher after blastocyst culture followed by transfer of blastocysts, and we have clinically encountered cases of 4-5 pregnancies after transfer of 2 embryos. Modern medicine has proved that multiple pregnancies are high-risk pregnancies with significantly increased risk of pregnancy and fetal complications, such as gestational hypertension syndrome, eclampsia, abnormal glucose tolerance during pregnancy, weak contractions during labor, surgical delivery and postpartum hemorrhage; fetal complications such as miscarriage, preterm labor and premature rupture of membranes, fetal malformation, twin fetal transfusion syndrome, intrauterine growth retardation, intrauterine fetal death, low birth weight fetus, neonatal asphyxia, and fetal death. The incidence of low birth weight and neonatal asphyxia increases. With shorter gestational weeks, neonatal complications and sequelae due to low birth weight increase, such as ophthalmologic abnormalities, respiratory distress syndrome, small bowel necrosis, and cerebral palsy. Furthermore, perinatal mortality is three times higher in twin pregnancies and five times higher in triplet pregnancies than in singleton pregnancies. One study showed that the incidence of preeclampsia was three times higher in twin pregnancies and nine times higher in triplet pregnancies than in singleton pregnancies. The mortality rate among pregnant women is 2.5 times higher in multiple pregnancies than in singleton pregnancies, and the symptoms of early pregnancy reactions (such as nausea and vomiting) are more pronounced in multiple pregnancies than in singleton pregnancies. Fetal mortality is higher in multiple pregnancies than in singleton pregnancies, and the risk of preterm delivery is significantly higher, 50% in twin pregnancies (10% of which occur before 32 weeks), and the incidence of preterm delivery increases with the number of fetuses. The perinatal morbidity and mortality rate of twin pregnancies also increases 3-6 times. What is more important to note is that with the change in social attitudes and lifestyle habits, senior pregnancy has become a trend, and once again, mothers-to-be are reminded that the risk of multiple pregnancies will increase as the age of the pregnant mother increases. At present, China stipulates that reduction is required for three or more pregnancies after assisted conception, therefore, most of the multiple pregnancies after assisted conception are twin pregnancies. An additional concern for mothers-to-be is the consistency of growth of the two babies. Inconsistent growth in twin pregnancies is a unique complication of twin pregnancies and refers to the inconsistency in the genotype, external manifestations and development of twins, which can occur for a variety of reasons, mainly clinically in terms of weight, and is diagnosed by the difference in birth weight. It is now generally accepted that twins with inconsistent growth have a poorer prognosis in the perinatal period and a higher incidence of maternal complications; and with increasing weight differences between twins, there is a corresponding increase in perinatal mortality. Monozygotic dizygotic growth disparities can occur at any time of gestation, whereas dizygotic dizygotic growth disparities usually occur in the middle to late stages of pregnancy. The earlier the onset of growth disparity in early pregnancy, the greater the weight difference, and the higher the perinatal mortality rate. Therefore, monitoring during pregnancy is more important for early detection and intervention. Currently, the fetal weight can be predicted by measuring the fetal head and hip length by ultrasound in the early stages and by measuring the fetal head circumference, abdominal circumference and femur length in the middle and late stages. Mothers with monozygotic twins should be monitored more intensively and pay more attention to maternal checkups. In addition, some studies have shown that obese and tall people are more likely to have twin pregnancies, especially dizygotic twin pregnancies, and that height is negatively associated with complications of twin pregnancies. Therefore, it is usually recommended that pregnant women below 160 cm in height should choose twin pregnancies with caution because of the increased complications during pregnancy and in the fetus in women with short stature. The goal of infertility treatment is not only to obtain a pregnancy, but more importantly, to obtain a safe pregnancy and a healthy newborn. Once a multiple pregnancy occurs, it is important for pregnant mothers to learn more about it and how to deal with it, to choose the number of pregnancies after weighing the risks and benefits, and to intensify maternal checkups during pregnancy.