What should you know about hatching blastocyst twins?

Hatching blastocyst twins are twins developing from embryos that are starting to emerge from their outer shell before implantation. A blastocyst is an early embryo made of an inner group of cells and an outer layer. Hatching helps the embryo attach to the lining of the womb. One blastocyst may divide into identical twins, while two blastocysts may result in non-identical twins.

The word hatching describes a stage of embryo development, not a warning sign by itself. Twin pregnancies need closer observation because the babies may share a placenta or an amniotic sac, or may have separate support structures. Ultrasound helps establish these details and follows growth, fluid levels and the babies’ wellbeing. The appearance of an embryo on an early scan cannot, on its own, predict every later pregnancy outcome.

Attend the scans and appointments offered by your maternity team. Ask whether the twins have separate or shared placentas and sacs, and which schedule of growth monitoring is appropriate. Take prescribed supplements as directed, report new symptoms, and discuss work, travel, activity and birth planning according to your pregnancy. A later Growth Scan may be used to compare each baby’s size and wellbeing.

Contact your maternity team promptly for vaginal bleeding, fluid leakage, significant abdominal pain, regular tightening, severe headache, vision changes, sudden swelling or reduced fetal movements later in pregnancy. Seek urgent help for heavy bleeding, severe pain, fainting or trouble breathing. These symptoms need assessment regardless of how the embryos were described on an early scan.

Ask: Do the twins share a placenta or an amniotic sac? How often will scans check growth and fluid? What symptoms should prompt an urgent call? When should we discuss birth options, including a Caesarean Section?