Question

Signals for parturition originate from
(A) Fully developed foetus only
(B) Placenta only
(C) Oxytocin released by maternal pituitary
(D) Both A and B

Answer 1

Parturition is the process of childbirth, which marks the ending of pregnancy. It results in the delivery of one or more babies by the mother's naturally vaginal opening or by medical intervention called a caesarean section or C-section in which the baby is delivered through surgery.

Complete answer:
In humans, pregnancy lasts for 40 weeks during which the foetus attains complete development. Sometimes, the baby will be delivered before 37 weeks of pregnancy making it a premature baby. At the time of birth, the first sign of parturition is labour pain, which is caused by the contraction of the uterus wall to push the baby out. The entire labour can be observed in three stages:
Dilation: The onset of labour triggers the dilation of the cervix that happens at two phases- active and latent phase. The active phase is from 0 to 4 cm cervix dilation, occurring for 4 to 6 hours. The dilation completes during the latent phase during which the cervix dilation is from 4 to 10 cm.
Expulsion: Once the cervix is dilated completely, the baby is set to be delivered. At this stage, there are active and passive phases. The passive phase is when the baby’s head starts moving towards the vaginal opening. The active phase begins once the mother starts feeling the need to contract the abdominal muscles along with the uterine contraction to deliver the baby. This stage lasts for about 45 min after which the baby gets delivered.
Placental: After the baby is born, the placenta and the membranes are delivered. They are delivered slowly or can be gently pulled by the doctors.

Thus, the signals of parturition originate from (D) both A and B.

Note:
Parturition by C-section is advised when the delivery possesses risks for the mother or the baby. Some of the complications in childbirth are as follows:

Foetal distress - slowing of baby’s heart beat
When the umbilical cord wraps around the baby’s neck
Breech pregnancy – when the baby’s head doesn’t move towards the vagina
Obstructed labor
Twin delivery
High blood pressure in mother