PREGNANCY 75 



on one side in tlie process of enlargement. These changes some- 

 times produce constipation, while in tlie later stages of pregnancy 

 pressure on the bladder may cause frequent micturition. The 

 general distension often causes a cracking of the skin in the 

 abdominal region. 



Other well-known indications of pregnancy in man are the 

 sensations of nausea sometimes followed by vomiting (the 

 " morning sickness ") which tends to occur from the second to the 

 third or fourth month, but not afterwards, and the general 

 circulatory disturbances which may cause haemorrhoids and 

 varicose veins, or induce local congestion in the face or other 

 parts of the body. The congestion of the mucosa around the 

 vaginal opening (Chadwick's sign) is another indication. A 

 slight pigmentation may occur on the forehead as well as around 

 the nipples. There is sometimes an enlargement of the th}Toid 

 gland similar to what occurs at menstruation. 



The slight fluttering movements in the abdomen, commonly 

 called the " quickening," are due to the foetal movements being 

 felt for the first time. They take place at about the eighteenth 

 to twentieth week, when, owing to the increased length of the 

 umbilical cord, the foetus can move freely. 



Duration of Pregnancy 



The average duration of human pregiiancy is estimated at 

 about 270 days or ten lunar months, or rather more than nine 

 calendar months. It is reckoned from the date of conception, 

 or if this is not known from the cessation of the last menstruation. 

 There is evidence that ovulation takes place most usually about 

 the eighteenth or nineteenth day after the beginning of men- 

 struation, so that the time for parturition may be expected, with 

 a fair degree of accuracy on about the 288th day after the com- 

 mencement of the last menstruation. It would appear, however, 

 as already indicated, that there is a good deal of variation in the 

 precise stage of the menstrual cycle at which fertilisation may 

 occur. Moreover, prolonged gestation is a not very uncommon 

 occurrence, with parturition at the 320th or even the 331st day, 

 and twelve-month pregnancies are not unknown (Siegel). On 

 the other hand, well-developed children may be born as early 

 as the 240th day (Williams). 



