The incidence of double ovulation

Whilst dizygotic twinning rates are well characterised, it is not known how many women will release two eggs during a menstrual cycle instead of one.This number will obviously be higher than the twinning rate since twins arise only if both eggs successfully fertilise and develop. With our database of ultrasound examinations we aim to determine the relative number of those who ovulate one or two eggs in a non-pregnant population. Correlation with the twinning rates may yield interesting clues on human fertility, and may help explain why rates of twinning vary so much between different racial groups.

Prediction of IVF pregnancy success using early ultrasound pregnancy markers

The corpus luteum (CL) is a vital hormone secreting structure which forms on the ovary at the point spot where an egg is released. It therefore reflects the number of eggs released where the presence of one CL would mean that one egg has been released.
The CL is a vital structure in early pregnancy since it is known to secrete progesterone which nourishes and supports early pregnancy. We have had an interest in investigating whether the presence of a larger CL in early pregnancy may protect the fetus and be associated with a lower risk of miscarriage.
Indeed, in a preliminary study of 235 cases there was a significantly increased risk of miscarriage associated with a small CL measured by ultrasound at 5-9 weeks of pregnancy. The miscarriage risk was 5.9% for CL diameters at >90th centile (i.e. large corpora lutea) and a 15.7% risk when the diameter was between the 40-60th centile. If the CL diameter was <10th centile, there was a 21.9% risk of miscarriage.
We believe that this sets the ground to be able to predict the risk of miscarriage in women who had undergone a frozen embryo transfer IVF cycle, and have a viable pregnancy demonstrated at a 6 week ultrasound. Frozen embryo transfer cycles would be expected to be mostly one corpus luteum present in the ovaries unlike fresh embryo transfer where the medications given initially produce multiple corpora lutea (treatment cycle cysts).
Specifically, we would like to examine whether CL diameter in association with, mean sac diameter-crown rump length, can together provide a good estimation of miscarriage risk in frozen embryo transfer cycle regimens in cases where there is one corpus luteum present (e.g. some clomiphene citrate cycles, or regimens where an embryo transfer is timed with the women's natural cycle). We will also examine whether day 15-17 hCG levels also adds to risk estimation.

Investigating the outcomes of twins discordance for size at 5-9 weeks gestation

Until recently, it was believed that the factors causing low birthweight came into play during the middle of pregnancy. Recently, several studies have pointed to factors occurring earlier during pregnancy.
The significance of finding that one twin is smaller than the other at ultrasound at 5-9 weeks is uncertain. It is a dilemma for the clinicians since whether it heralds a poorer outcome, which some suspect, is far from certain. We hypothesis that in situations where one twin is found to be much smaller than the co-twin as early as 5-9 weeks of pregnancy, there will be an increased risk of low birthweight and chromosomal abnormalities in the smaller twin.
We plan to investigate this hypothesis in an IVF cohort. Should we show that this is the case, then the information gained from this study will have direct implications on how IVF clinicians counsel patients when faced with this ultrasound finding.

Determining zygosity by early ultrasound

Recently, we have published a novel method to determine whether twins are identical (monozygotic) or non-identical (dizygotic) at an early pregnancy ultrasound by noting the number of corpora lutea (CL), a structure which reflects ovulation (egg release). In the presence of a dichorionic twin pregnancy (which can be either monozygotic or dizygotic), the identification of one CL would suggest that twins are monozygotic whereas two CL's implies dizygosity. If need be, this could be further correlated against chorionicity where, for instance, 2 CL's (presumed Dz) and monochorionicity (certain Mz twins) would suggest that the predicted zygosity is incorrect.
However, this clearly requires verification. We are in the process of prospectively comparing ultrasound prediction of zygosity at 5-9 weeks of gestation with DNA fingerprinting of twins after delivery.

Low gestation sac and prediction of placenta Praevia

This is a prospective study which sets out to establish the range of distances of the gestation sac from the internal cervical os in the first trimester and determine the relationship between this measurement and the later development of placenta praevia.

Third Trimester Doppler studies of the fetal Middle Cerebral Artery

A prospective study which aims to establish the reference range of the fetal middle cerebral artery blood flow in a multiracial population and to compare this data with a population of pregnancies complicated with symmetrical and asymmetrical intrauterine growth retardation.
Size of the corpus luteum during the first trimester of pregnancy We are collecting a large dataset characterising the size of the corpus luteum at 5-13 weeks of gestation from over 1200 pregnancies. We aim to see whether it begins to regress at the end of the 1st trimester when the fetus becomes less dependent on its secretion of progesterone.

Intranasal (NET S21405 2575ug) and Endometrial response

A multicentre collaborative trial which aims to determine the effect on the endometrium of a new intranasal HRT preparation NET S2140. Secondary evaluation criteria include presence of endometrial hyperplasia after one year of treatment, vaginal bleeding pattern, endometrial histology, general tolerance and kinetic profile.