Pregnancy, Growth and Development: Labor and Delivery

Twins Dizygotic or fraternal twins occur when two separate eggs are ovulated. May be of different sexes. Monozygotic or identical twins occur when a single egg is fertilized but dividing cells break into two groups and develop into two individuals. Genetically identical (clones) fjigsUhttps:// fjigsU

Implantation can also occur in uterine tube, cervix, or the abdominal cavity. Implantation anywhere outside the uterus is called an ectopic pregnancy. It is possible for fetus to grow in the abdominal cavity, but growth inside the uterine tube causes the tube to rupture, resulting in severe bleeding. czWiWIhttps:// czWiWI

Ectopic pregnancy sites

Gestation period Divided into three trimesters. During first trimester individual starts out as a zygote, then morula, blastocyst, and after implantation, is called an embryo. Embryonic phase of development lasts from fertilization until the 8 th week of gestation, when it becomes a fetus. By day 35 the heart is beating, and eye and limb buds are present.

By month four, the rudiments of all organ systems are formed and functioning, and from then on, fetal development is primarily a matter of growth. By the end of the third month the placenta is functioning.

Quickening The first movement of the fetus felt by the mother, usually occurring during the fourth or fifth month of pregnancy By month seven the fetus is quite active During the last month the fetus becomes less active (usually due to space considerations.)

At the end of pregnancy both the mother and the uterus become “irritable” The uterus undergoes Braxton-Hicks contractions: intermittent, painless contractions which can come 10 to 20 minutes apart. Become more frequent as gestation progresses, and can be mistaken for onset of labor Cervix begins to thin and dilate

Labor (parturition) Stage one – the period from the onset of true labor contractions until the cervix is completely dilated at 10 cm. The uterine contractions cause the cervix to dilate, and the amniotic sac may rupture. Usually lasts 6 – 24 hours depending on the number of previous deliveries.

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Stage 2 Period from maximal cervical dilation until the birth of the baby Lasts minutes to an hour Contractions become more intense and frequent.

Stage 3 The expulsion of the placenta Usually occurs within 15 minutes after the birth of the baby, but can range from 5 to 60 minutes.