Pregnancies

Pregnancy is the period during which a fertilized egg implants and develops into a fetus inside the uterus. In humans it typically lasts about 40 weeks from the first day of the last menstrual period, or roughly 38 weeks from conception. The terms gravidity and parity describe how many pregnancies a person has had and how many have progressed past viability, respectively.

Prenatal care starts early and continues through delivery. It includes regular medical checkups, screening tests, and guidance on nutrition, physical activity, and avoidance of harmful substances. Common interventions include folic acid supplementation before and during early pregnancy, vaccination as appropriate, and screening for conditions such as anemia, infections, and fetal growth via ultrasound and laboratory tests. The pregnancy is conventionally divided into three trimesters: first (weeks 1–12), second (weeks 13–27), and third (weeks 28–40).

During development, the embryo forms major organs in the first trimester, and growth accelerates in the second trimester with continued maturation of organ systems. The third trimester concentrates on weight gain and preparing for birth. Maternal changes include hormonal shifts that can affect mood, energy, and sleep, as well as physical changes such as weight gain and abdominal enlargement.

Most pregnancies proceed without major complications, but risks exist. Common concerns include miscarriage or ectopic pregnancy, gestational diabetes, preeclampsia, placenta previa, and preterm birth. Labor marks the start of birth, with contractions and cervical dilation leading to vaginal delivery or cesarean section. The postpartum period follows birth, focusing on recovery, newborn care, and bonding and often lactation.