=At the end of the ninth month, or thirty-sixth week=, the increased amount of fat under the baby’s skin has given a plumper, rounder contour to the entire body; the aged look has passed and his chances for life have greatly increased. He weighs about 5½ pounds at this stage and is perhaps 18 inches long. =The end of the tenth month, or fortieth week=, usually marks the end of pregnancy. Fig. 9 will show you how the baby lies in the uterus just before birth, curled up into the smallest possible space. [Illustration: FIG. 9.—The usual position of the baby just before he is born. ] The average normally developed baby has grown to a length of about 20 inches and weighs about 7¼ pounds, boys usually being about three ounces heavier than girls, but there may be a variation of weight among entirely normal, healthy babies from a minimum of 5 pounds to as high as 11 pounds or more. Newborn babies very seldom weigh more than 12 pounds, in spite of legends and rumors to the contrary. The size of the baby is affected by the race of his parents; colored babies, for example, averaging a smaller weight than white babies. And, as might be expected, the size of the parents is likely to be reflected in their infants, large parents tending to have large children and vice versa. The number of children which the mother has previously borne is also a factor, since the first child is usually the smallest, the size of those following showing an increase with the mother’s age up to her twenty-eighth year, if her pregnancies do not occur at too frequent intervals. =Twins.= Sometimes a woman gives birth to more than one baby at the same time. When there are two they are called twins; triplets when there are three; quadruplets, quintuplets and sextuplets respectively, when there are four, five and six babies within the uterus at once. Six is the largest accredited number on record. It is estimated that twins occur once in ninety pregnancies and triplets once in about seven thousand cases. The tendency seems to be inherited, as is evidenced by the number of twins and triplets to be found among relatives. Twins are often prematurely born and each is likely to be smaller than a baby resulting from a single pregnancy, but their combined weight is greater than the weight of one normal baby.