Modes of conception and multiple pregnancy: a national survey of babies born during one week in 2003 in the United Kingdom.

OBJECTIVE

To collect data on every baby born in one week in the United Kingdom with respect to mode of conception, multiplicity of pregnancy, and outcome.

DESIGN

A questionnaire completed by the midwife birth attendant.

SETTING

All maternity units in the United Kingdom.

PATIENT(S): All mothers delivering during the week of April 6-12, 2003.

INTERVENTION(S): Questionnaire survey.

MAIN OUTCOME MEASURE(S): Mode of conception (both spontaneous and assisted), type of fertility treatment, multiplicity of pregnancy, mode of delivery, gestational age, and fetal outcome.

RESULT(S): Data were received from 178 maternity units (72.7%) on 6,913 deliveries: 6,812 (98.54%) were singleton, 100 (1.45%) twin, and 1 (0.01%) triplet. In total, 7,015 babies were born. Of all pregnancies, 6,638 (96%) (including the only triplet) were conceived spontaneously and 133 (1.9%) with assistance. The multiple pregnancy rate was significantly greater in assisted (13.5%) than in spontaneous (1.2%) conceptions. Of the multiple pregnancies after fertility treatment, 16.7% resulted from clomifene citrate therapy, 72.2% from IVF or frozen embryo replacements (FET), and 5.6% from superovulation with intrauterine insemination (IUI). The multiple pregnancy rate after IVF/FET (26%) was significantly higher than the one after clomifene citrate therapy (7.3%). In total, 41 babies were born after clomifene citrate therapy, 50 after IVF/ET, and eight after superovulation IUI. The live birth rate was higher for singleton (98.2%) than multiple pregnancies (93.6%).

CONCLUSION(S): Multiple pregnancy from IVF and related treatments remains a significant problem and contributes a greater burden than ovulation induction therapies.