Pregnant women over 35 years old are more likely to have complications during delivery due to delayed and longer labour stages as their uterus can contract, reveals a study.
The findings, published in the journal of Physiology, suggest that older women are also more at risk of requiring a caesarean section or instrumented delivery (e.g., with forceps), suggesting there may be issues with the way their uterus can contract during labour.
"Our research highlights that there are key physiological and cellular changes associated with a mother's age that result in labour dysfunction - an abnormal, long, or difficult labor or delivery. Timing of delivery and progress of labour is directly related to maternal age and this can cause complications during birth," said lead author Dr Rachel M. Tribe. The pregnancy complications include induction for women, who have passed their due date, failure to progress in labour and bleeding after delivery.
The average mouse has a peak fertile period between three to five months, so mice at eight months were used to represent an older mother. They analysed the functions and physiological changes in the cervix and uterine muscles from these pregnant mice. The study found that in older mice, muscle contraction properties in the uterus were impaired, less sensitive to oxytocin and had reduced numbers of mitochondria indicating the uterus muscles are less able to contract.
They also found altered hormonal signals underpinned the delayed onset of labour. Signalling of the pregnancy-related hormone progesterone was also altered and this triggered a delay in labour.