answers: blighted ovum or anembryonic gestation
context: an embryo whose crown–rump length is 15 mm or more has no visible cardiac activity. Blighted ovum A blighted ovum or anembryonic gestation (anembryonic pregnancy) is a pregnancy in which the embryo never develops or develops and is reabsorbed. It typically results in a miscarriage. In a normal pregnancy, an embryo would be visible on an ultrasound by six weeks after the woman's last menstrual period. Anembryonic gestation is one of the causes of miscarriage of a pregnancy. A blighted ovum or anembryonic gestation is characterized by a normal-appearing gestational sac, but the absence of an embryo. It likely occurs </s> ovarian surface, perhaps aided by a decidual reaction or endometriosis. Ovarian pregnancies rarely go longer than 4 weeks; nevertheless, there is the possibility that the trophoblast finds further support outside the ovary and thus may affect the tube and other organs. In very rare occasions the pregnancy may find a sufficient foothold outside the ovary to continue as an abdominal pregnancy, and an occasional delivery has been reported. The diagnosis is made in asymptomatic pregnant women by obstetric ultrasonography. On pelvic examination a unilateral adnexal mass may be found. Typical symptoms are abdominal pain and, to a lesser degree, vaginal </s> Preterm birth Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks' gestational age. These babies are known as preemies or premies. Symptoms of preterm labor include uterine contractions which occur more often than every ten minutes or the leaking of fluid from the vagina. Premature infants are at greater risk for cerebral palsy, delays in development, hearing problems and sight problems. These risks are greater the earlier a baby is born. The cause of preterm birth is often not known. Risk factors include diabetes, high blood pressure, being pregnant with more
question: gestational sac but no yolk sac and embryo