predisposing factors for multiple pregnancy
Last reviewed 04/2023
- overall background rates (UK)
- twins 1 in 105 births
- triplets 1 in 10 000 births
- quadruplets 1 in 500 000 births
- maternal age:
- < 20 years, 6.4 per 1000 births
- > 40 years, 16.8 per 1000 births
- parity
- para 0, 9.8 per 1000 births
- para 7, 18.0 per 1000 births
- family history: maternal, binovular, 5-15% incidence
- race:
- Afro-carribean 1 in 60 twins
- Japanese 1 in 154 twins
- Induced ovulation:
- Human ant. pit. 44% multiple
- purified HMG and HCG 10% multiple
- clomiphene 10% multiple