Pregnancy

Pregnancy is the fertilization and development of one or more offspring, known as an embryo or foetus, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Childbirth usually occurs about 38 weeks after conception; in women who have a menstrual cycle length of four weeks, this is approximately 40 weeks from the start of the last normal menstrual period (LNMP). Human pregnancy is the most studied of all mammalian pregnancies.

An embryo is the developing offspring during the first 8 weeks following conception, and subsequently the term foetus is used until birth. Human pregnancy is divided into three trimester periods. The first trimester carries the highest risk of miscarriage (natural death of embryo or foetus). During the second trimester, the development of the foetus can be more easily monitored and diagnosed. The beginning of the third trimester often approximates the point of viability, or the ability of the foetus to survive, with or without medical help, outside of the uterus.

There are generally three different dates as the start of pregnancy:

Since these are spread over a significant period of time, the duration of pregnancy necessarily depends on the date selected as the starting point chosen.

A woman is considered to be in labour when she begins experiencing regular uterine contractions, accompanied by changes of her cervix – primarily effacement and dilation. While childbirth is widely experienced as painful, some women do report painless labours, while others find that concentrating on the birth helps to quicken labour and lessen the sensations. Most births are successful vaginal births, but sometimes complications arise and a woman may undergo a caesarean section.

During the time immediately after birth, both the mother and the baby are hormonally cued to bond, the mother through the release of oxytocin, a hormone also released during breastfeeding. Studies show that skin-to-skin contact between a mother and her newborn immediately after birth is beneficial for both the mother and baby. A review done by the World Health Organization found that skin-to-skin contact between mothers and babies after birth reduces crying, improves mother-infant interaction, and helps mothers to breastfeed successfully. They recommend that neonates be allowed to bond with the mother during their first two hours after birth, the period that they tend to be more alert than in the following hours of early life.

Different stages of Pregnancy